SUSTAINABILITY Planetary boundaries: Guiding human ...

12
RESEARCH ARTICLE SUMMARY SUSTAINABILITY Planetary boundaries: Guiding human development on a changing planet Will Steffen,* Katherine Richardson, Johan Rockström, Sarah E. Cornell, Ingo Fetzer, Elena M. Bennett, Reinette Biggs, Stephen R. Carpenter, Wim de Vries, Cynthia A. de Wit, Carl Folke, Dieter Gerten, Jens Heinke, Georgina M. Mace, Linn M. Persson, Veerabhadran Ramanathan, Belinda Reyers, Sverker Sörlin INTRODUCTION: There is an urgent need for a new paradigm that integrates the continued development of human societies and the main- tenance of the Earth system (ES) in a resilient and accommodating state. The planetary bound- ary (PB) framework contributes to such a paradigm by providing a science-based analysis of the risk that human perturbations will de- stabilize the ES at the planetary scale. Here, the scientific underpinnings of the PB framework are updated and strengthened. RATIONALE: The relatively stable, 11,700-year- long Holocene epoch is the only state of the ES that we know for certain can support contem- porary human societies. There is increasing evi- dence that human activities are affecting ES functioning to a degree that threatens the re- silience of the ESits ability to persist in a Holocene-like state in the face of increasing human pressures and shocks. The PB frame- work is based on critical processes that reg- ulate ES functioning. By combining improved scientific understanding of ES functioning with the precautionary principle, the PB framework identifies levels of anthropogenic perturbations below which the risk of destabilization of the ES is likely to remain lowa safe operating spacefor global societal development. A zone of uncertainty for each PB highlights the area of increasing risk. The current level of anthro- pogenic impact on the ES, and thus the risk to the stability of the ES, is assessed by compar- ison with the proposed PB (see the figure). RESULTS: Three of the PBs (climate change, stratospheric ozone depletion, and ocean acid- ification) remain essentially unchanged from the earlier analysis. Regional-level boundaries as well as globally aggregated PBs have now been developed for biosphere integrity (earlier biodiversity loss), biogeochemical flows, land- system change, and freshwater use. At present, only one regional boundary (south Asian mon- soon) can be established for atmospheric aerosol loading. Although we cannot identify a single PB for novel entities (here de- fined as new substances, new forms of existing sub- stances, and modified life forms that have the po- tential for unwanted geo- physical and/or biological effects), they are included in the PB framework, given their potential to change the state of the ES. Two of the PBsclimate change and bio- sphere integrityare recognized as corePBs based on their fundamental importance for the ES. The climate system is a manifestation of the amount, distribution, and net balance of energy at Earths surface; the biosphere regulates ma- terial and energy flows in the ES and increases its resilience to abrupt and gradual change. Anthropogenic perturbation levels of four of the ES processes/features (climate change, bio- sphere integrity, biogeochemical flows, and land- system change) exceed the proposed PB (see the figure). CONCLUSIONS: PBs are scientifically based levels of human perturbation of the ES beyond which ES functioning may be substantially altered. Transgression of the PBs thus creates substantial risk of destabilizing the Holocene state of the ES in which modern societies have evolved. The PB framework does not dictate how societies should develop. These are po- litical decisions that must include considera- tion of the human dimensions, including equity, not incorporated in the PB framework. Never- theless, by identifying a safe operating space for humanity on Earth, the PB framework can make a valuable contribution to decision- makers in charting desirable courses for socie- tal development. RESEARCH 736 13 FEBRUARY 2015 VOL 347 ISSUE 6223 sciencemag.org SCIENCE Current status of the control variables for seven of the planetary boundaries. The green zone is the safe operating space, the yellow represents the zone of uncertainty (increasing risk), and the red is a high-risk zone.The planetary boundary itself lies at the intersection of the green and yellow zones. The control variables have been normalized for the zone of uncertainty; the center of the figure therefore does not represent values of 0 for the control variables.The control variable shown for climate change is atmospheric CO 2 concentration. Processes for which global-level boundaries cannot yet be quantified are represented by gray wedges; these are atmospheric aerosol loading, novel entities, and the functional role of biosphere integrity. The list of author affiliations is available in the full article online. *Corresponding author. E-mail: [email protected] Cite this article as W. Steffen et al., Science 347, 1259855 (2015). DOI: 10.1126/science.1259855 ON OUR WEB SITE Read the full article at http://dx.doi. org/10.1126/ science.1259855 .................................................. on February 13, 2015 www.sciencemag.org Downloaded from on February 13, 2015 www.sciencemag.org Downloaded from on February 13, 2015 www.sciencemag.org Downloaded from on February 13, 2015 www.sciencemag.org Downloaded from on February 13, 2015 www.sciencemag.org Downloaded from on February 13, 2015 www.sciencemag.org Downloaded from on February 13, 2015 www.sciencemag.org Downloaded from on February 13, 2015 www.sciencemag.org Downloaded from on February 13, 2015 www.sciencemag.org Downloaded from on February 13, 2015 www.sciencemag.org Downloaded from on February 13, 2015 www.sciencemag.org Downloaded from

Transcript of SUSTAINABILITY Planetary boundaries: Guiding human ...

RESEARCH ARTICLE SUMMARY

SUSTAINABILITY

Planetary boundaries Guidinghuman development on achanging planetWill Steffen Katherine Richardson Johan Rockstroumlm Sarah E Cornell Ingo FetzerElena M Bennett Reinette Biggs Stephen R Carpenter Wim de VriesCynthia A de Wit Carl Folke Dieter Gerten Jens Heinke Georgina M MaceLinn M Persson Veerabhadran Ramanathan Belinda Reyers Sverker Soumlrlin

INTRODUCTION There is an urgent need fora new paradigm that integrates the continueddevelopment of human societies and the main-tenance of the Earth system (ES) in a resilientandaccommodating state Theplanetarybound-ary (PB) framework contributes to such aparadigm by providing a science-based analysisof the risk that human perturbations will de-stabilize the ES at the planetary scale Here thescientific underpinnings of the PB frameworkare updated and strengthened

RATIONALE The relatively stable 11700-year-longHolocene epoch is the only state of the ES

that we know for certain can support contem-porary human societies There is increasing evi-dence that human activities are affecting ESfunctioning to a degree that threatens the re-silience of the ESmdashits ability to persist in aHolocene-like state in the face of increasinghuman pressures and shocks The PB frame-work is based on critical processes that reg-ulate ES functioning By combining improvedscientific understanding of ES functioningwiththe precautionary principle the PB frameworkidentifies levels of anthropogenic perturbationsbelow which the risk of destabilization of theES is likely to remain lowmdasha ldquosafe operating

spacerdquo for global societal development A zoneof uncertainty for each PB highlights the areaof increasing risk The current level of anthro-pogenic impact on the ES and thus the risk tothe stability of the ES is assessed by compar-ison with the proposed PB (see the figure)

RESULTS Three of the PBs (climate changestratospheric ozone depletion and ocean acid-ification) remain essentially unchanged fromthe earlier analysis Regional-level boundariesas well as globally aggregated PBs have nowbeen developed for biosphere integrity (earlierldquobiodiversity lossrdquo) biogeochemical flows land-system change and freshwater use At presentonly one regional boundary (south Asian mon-soon) can be established for atmospheric aerosolloading Althoughwe cannot identify a single PB

for novel entities (here de-fined as new substancesnew forms of existing sub-stances and modified lifeforms that have the po-tential for unwanted geo-physical andor biological

effects) they are included in the PB frameworkgiven their potential to change the state of theES Two of the PBsmdashclimate change and bio-sphere integritymdashare recognized as ldquocorerdquo PBsbased on their fundamental importance for theES The climate system is a manifestation of theamount distribution and net balance of energyat Earthrsquos surface the biosphere regulates ma-terial and energy flows in the ES and increasesits resilience to abrupt and gradual changeAnthropogenic perturbation levels of four ofthe ES processesfeatures (climate change bio-sphere integrity biogeochemical flows and land-system change) exceed the proposed PB (see thefigure)

CONCLUSIONS PBs are scientifically basedlevels of human perturbation of the ES beyondwhich ES functioning may be substantiallyaltered Transgression of the PBs thus createssubstantial risk of destabilizing the Holocenestate of the ES in which modern societies haveevolved The PB framework does not dictatehow societies should develop These are po-litical decisions that must include considera-tion of the human dimensions including equitynot incorporated in the PB framework Never-theless by identifying a safe operating spacefor humanity on Earth the PB frameworkcan make a valuable contribution to decision-makers in charting desirable courses for socie-tal development

RESEARCH

736 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 sciencemagorg SCIENCE

Current status of the control variables for seven of the planetary boundariesThe green zoneis the safe operating space the yellow represents the zone of uncertainty (increasing risk) and thered is a high-risk zoneThe planetary boundary itself lies at the intersection of the green and yellowzones The control variables have been normalized for the zone of uncertainty the center of thefigure therefore does not represent values of 0 for the control variablesThe control variable shownfor climate change is atmospheric CO2 concentration Processes for which global-level boundariescannot yet be quantified are represented by gray wedges these are atmospheric aerosol loadingnovel entities and the functional role of biosphere integrity

The list of author affiliations is available in the full article onlineCorresponding author E-mail willsteffenanueduauCite this article as W Steffen et al Science 347 1259855(2015) DOI 101126science1259855

ON OUR WEB SITE

Read the full articleat httpdxdoiorg101126science1259855

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RESEARCH ARTICLE

SUSTAINABILITY

Planetary boundaries Guidinghuman development on achanging planetWill Steffen12 Katherine Richardson3 Johan Rockstroumlm1 Sarah E Cornell1

Ingo Fetzer1 Elena M Bennett4 Reinette Biggs15 Stephen R Carpenter6

Wim de Vries78 Cynthia A de Wit9 Carl Folke110 Dieter Gerten11 Jens Heinke111213

Georgina M Mace14 Linn M Persson15 Veerabhadran Ramanathan1617

Belinda Reyers118 Sverker Soumlrlin19

The planetary boundaries framework defines a safe operating space for humanity basedon the intrinsic biophysical processes that regulate the stability of the Earth systemHere we revise and update the planetary boundary framework with a focus on theunderpinning biophysical science based on targeted input from expert researchcommunities and on more general scientific advances over the past 5 years Several of theboundaries now have a two-tier approach reflecting the importance of cross-scaleinteractions and the regional-level heterogeneity of the processes that underpin theboundaries Two core boundariesmdashclimate change and biosphere integritymdashhave beenidentified each of which has the potential on its own to drive the Earth system into a newstate should they be substantially and persistently transgressed

The planetary boundary (PB) approach (1 2)aims to define a safe operating space forhumansocieties to develop and thrive basedon our evolving understanding of the func-tioning and resilience of the Earth system

Since its introduction the framework has beensubject to scientific scrutiny [eg (3ndash7)] and hasattracted considerable interest and discussionswithin the policy governance and business sec-tors as an approach to inform efforts toward glob-al sustainability (8ndash10)In this analysis we further develop the basic

PB framework by (i) introducing a two-tier ap-proach for several of the boundaries to accountfor regional-level heterogeneity (ii) updating thequantification ofmost of the PBs (iii) identifyingtwo core boundaries and (iv) proposing a regional-level quantitative boundary for one of the twothat were not quantified earlier (1)

The basic framework Defininga safe operating space

Throughout history humanity has faced environ-mental constraints at local and regional levelswith some societies dealing with these challengesmore effectively than others (11 12) More recent-ly early industrial societies often used local water-ways and airsheds as dumping grounds for theirwaste and effluent from industrial processes Thiseroded local and regional environmental qualityand stability threatening to undermine the pro-gress made through industrialization by damag-ing human health and degrading ecosystemsEventually this led to the introduction of localor regional boundaries or constraints on what

could be emitted to and extracted from the en-vironment (eg chemicals that pollute airshedsor waterways) and on howmuch the environmentcould be changed by direct human modification(land-usecover change in natural ecosystems)(13) The regulation of some human impacts onthe environmentmdashfor example the introductionof chemical contaminantsmdashis often framed inthe context of ldquosafe limitsrdquo (14)These issues remain but in addition we now

face constraints at the planetary level where themagnitude of the challenge is vastly differentThe humanenterprise has grown so dramaticallysince themid-20th century (15) that the relativelystable 11700-year-long Holocene epoch the onlystate of the planet that we know for certain cansupport contemporary human societies is nowbeing destabilized (figs S1 and S2) (16ndash18) Infact a new geological epoch the Anthropocenehas been proposed (19)The precautionary principle suggests that hu-

man societies would be unwise to drive the Earthsystem substantially away from a Holocene-likecondition A continuing trajectory away from theHolocene could lead with an uncomfortably highprobability to a very different state of the Earthsystem one that is likely to be much less hos-pitable to the development of human societies(17 18 20) The PB framework aims to help guidehuman societies away from such a trajectory bydefining a ldquosafe operating spacerdquo inwhichwe cancontinue to develop and thrive It does this byproposing boundaries for anthropogenic pertur-bation of critical Earth-systemprocesses Respect-ing these boundaries would greatly reduce the

risk that anthropogenic activities could inadver-tently drive the Earth system to a much less hos-pitable stateNine processes each of which is clearly being

modified by human actions were originally sug-gested to form the basis of the PB framework (1)Although these processes are fundamental toEarth-system functioning there are many otherways that Earth-system functioning could be de-scribed including potentially valuable metricsfor quantifying the human imprint on it Thesealternative approaches [eg (4)] often representways to explore and quantify interactions amongthe boundaries They can provide a valuable com-plement to the original approach (1) and furtherenrich the broader PB concept as it continues toevolve

The planetary boundaryframework Thresholds feedbacksresilience uncertainties

A planetary boundary as originally defined (1) isnot equivalent to a global threshold or tippingpoint As Fig 1 shows even when a global- orcontinentalocean basinndashlevel threshold in anEarth-system process is likely to exist [eg (20 21)]the proposed planetary boundary is not placedat the position of the biophysical threshold butrather upstream of itmdashie well before reachingthe threshold This buffer between the boundary(the end of the safe operating space the greenzone in Fig 1) and the threshold not only ac-counts for uncertainty in the precise position ofthe threshold with respect to the control variable

RESEARCH

SCIENCE sciencemagorg 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 1259855-1

1Stockholm Resilience Centre Stockholm University 10691Stockholm Sweden 2Fenner School of Environment andSociety The Australian National University Canberra ACT 2601Australia 3Center for Macroecology Evolution and ClimateUniversity of Copenhagen Natural History Museum of DenmarkUniversitetsparken 15 Building 3 2100 Copenhagen Denmark4Department of Natural Resource Sciences and McGill School ofEnvironment McGill University 21 111 Lakeshore Road Ste-Anne-de-Bellevue QC H9X 3V9 Canada 5Centre for Studies inComplexity Stellenbosch University Private Bag X1Stellenbosch 7602 South Africa 6Center for LimnologyUniversity of Wisconsin 680 North Park Street Madison WI53706 USA 7Alterra Wageningen University and ResearchCentre PO Box 47 6700AA Wageningen Netherlands8Environmental Systems Analysis Group Wageningen UniversityPO Box 47 6700 AA Wageningen Netherlands 9Departmentof Environmental Science and Analytical Chemistry StockholmUniversity 10691 Stockholm Sweden 10Beijer Institute ofEcological Economics Royal Swedish Academy of SciencesSE-10405 Stockholm Sweden 11Research Domain EarthSystem Analysis Potsdam Institute for Climate ImpactResearch (PIK) Telegraphenberg A62 14473 PotsdamGermany 12International Livestock Research Institute POBox 30709 Nairobi 00100 Kenya 13CSIRO (CommonwealthScientific and Industrial Research Organization) St LuciaQLD 4067 Australia 14Centre for Biodiversity andEnvironment Research (CBER) Department of GeneticsEvolution and Environment University College London GowerStreet London WC1E 6BT UK 15Stockholm EnvironmentInstitute Linneacutegatan 87D SE-10451 Stockholm Sweden16Scripps Institution of Oceanography University of Californiaat San Diego 8622 Kennel Way La Jolla CA 92037 USA17TERI (The Energy and Resources Institute) University 10Institutional Area Vasant Kunj New Delhi Delhi 110070India 18Natural Resources and the Environment CSIR POBox 320 Stellenbosch 7599 South Africa 19Division ofHistory of Science Technology and Environment KTH RoyalInstitute of Technology SE-10044 Stockholm SwedenCorresponding author E-mail willsteffenanueduau

but also allows society time to react to early warn-ing signs that it may be approaching a thresh-old and consequent abrupt or risky changeThe developing science of early-warning signs

can warn of an approaching threshold or a de-crease in the capability of a system to persistunder changing conditions Examples includeldquocritical slowing downrdquo in a process (22) in-creasing variance (23) and flickering betweenstates of the system (24ndash26) However for suchscience to be useful in a policy context it mustprovide enough time for society to respond inorder to steer away from an impending thresh-old before it is crossed (27 28) The problem ofsystem inertiamdashfor example in the climate sys-tem (18)mdashneeds to be taken into account in as-sessing the time needed for society to react toearly-warning signsNot all Earth-system processes included in the

PBapproachhave singular thresholds at the globalcontinentalocean basin level (1) Nevertheless itis important that boundaries be established forthese processes They affect the capacity of theEarth system to persist in a Holocene-like stateunder changing conditions (henceforth ldquoresiliencerdquo)by regulating biogeochemical flows (eg the ter-restrial andmarine biological carbon sinks) or byproviding the capacity for ecosystems to tolerateperturbations and shocks and to continue func-tioning under changing abiotic conditions (29 30)Examples of such processes are land-systemchange freshwater use change in biosphere in-tegrity [rate of biodiversity loss in (1 2)] andchanges in other biogeochemical flows in addi-tion to carbon (eg nitrogen and phosphorus)Placing boundaries for these processes is more

difficult than for those with known large-scalethresholds (21) but is nevertheless important formaintaining the resilience of the Earth system asa whole As indicated in Fig 1 these processesmany of which show threshold behavior at localand regional scales can generate feedbacks tothe processes that do have large-scale thresholdsThe classic example is the possible weakening ofnatural carbon sinks which could further de-stabilize the climate system and push it closer tolarge thresholds [eg loss of the Greenland icesheet (18)] An interesting research question ofrelevance to the PB framework is how small-scale regime shifts can propagate across scalesand possibly lead to global-level transitions (31 32)A zone of uncertainty sometimes large is as-

sociatedwith each of the boundaries (yellow zonein Fig 1) This zone encapsulates both gaps andweaknesses in the scientific knowledge base andintrinsic uncertainties in the functioning of theEarth system At the ldquosaferdquo end of the zone of un-certainty current scientific knowledge suggeststhat there is very low probability of crossing acritical threshold or substantially eroding the re-silience of the Earth system Beyond the ldquodangerrdquoend of the zone of uncertainty current knowl-edge suggests a much higher probability of achange to the functioning of the Earth systemthat could potentially be devastating for humansocieties Application of the precautionary prin-ciple dictates that the planetary boundary is setat the ldquosaferdquo end of the zone of uncertainty Thisdoes notmean that transgressing a boundarywillinstantly lead to an unwanted outcome but thatthe farther the boundary is transgressed thehigher the risk of regime shifts destabilized sys-

tem processes or erosion of resilience and thefewer the opportunities to prepare for suchchanges Observations of the climate system showthis principle in action by the influence of in-creasing atmospheric greenhouse gas concentra-tions on the frequency and intensity of manyextreme weather events (17 18)

Linking global and regional scales

PB processes operate across scales from oceanbasinsbiomes or sourcessinks to the level of theEarth system as a whole Here we address thesubglobal aspects of the PB framework Rock-stroumlm et al (1) estimated global boundaries on-ly acknowledging that the control variables formany processes are spatially heterogeneous Thatis changes in control variables at the subgloballevel can influence functioning at the Earth-system level which indicates the need to definesubglobal boundaries that are compatible withthe global-level boundary definition Avoidingthe transgression of subglobal boundaries wouldthus contribute to an aggregate outcome withina planetary-level safe operating spaceWe focus on the five PBs that have strong re-

gional operating scales biosphere integrity biogeo-chemical flows [earlier termed ldquophosphorus (P)andnitrogen (N) cyclesrdquo (12)] land-systemchangefreshwater use and atmospheric aerosol loadingTable S1 describes how transgression of any ofthe proposed boundaries at the subglobal levelaffects the Earth system at the global levelFor those processes where subglobal dynamics

potentially play a critical role in global dynamicsthe operational challenge is to capture the im-portance of subglobal change for the functioning

1259855-2 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 sciencemagorg SCIENCE

Fig 1 The conceptual framework for the planetary boundary approach showing the safe operating space the zone of uncertainty the position ofthe threshold (where one is likely to exist) and the area of high riskModified from (1)

RESEARCH | RESEARCH ARTICLE

of the Earth system To do this we propose thedevelopment of a two-level set of control var-iables and boundaries The subglobal-level unitsof analysis for these six boundaries are notidentical they vary according to the role that theprocesses play in the Earth system (i) changesin biosphere integrity occur at the level of land-based biomes large freshwater ecosystems ormajor marine ecosystems as the largest sub-global unit (ii) the role of direct human-drivenland-system change in biophysical climate regu-lation is primarily related to changes in forestbiomes (iii) freshwater flows and use occur atthe largest subglobal level in the major riverbasins around the world and (iv) changes inbiogeochemical flows exemplified by phospho-rus and nitrogen cycling aggregate from rela-tively localized but very severe perturbationsin intensive agricultural zones to affect globalflows of nutrients We recognize these as crit-ical regions for Earth-system functioningWhereappropriate the updates of the individual bound-aries (see below) (33) now contain both the glob-ally aggregated boundary value of the controlvariable and its regional distribution functionFigure 2 shows the distributions and currentstatus of the control variables for three of theboundaries where subglobal dynamics are crit-

ical biogeochemical cycles land-system changeand freshwater useWe emphasize that our subglobal-level focus is

based on the necessity to consider this level tounderstand the functioning of the Earth systemas awhole The PB framework is thereforemeantto complement not replace or supersede effortsto address local and regional environmental issues

Updates of the individual boundaries

Brief updates of all nine of the PBs are given inthis section and more detailed descriptions ofthe updates for three of the PBs that have under-gone more extensive revision can be found in (33)The geographical distribution issues discussedabove are particularly important for five of thePBs and their control variables and boundarieshave been revised accordingly (Table 1) Figure 3shows the current status of the seven bounda-ries that can be quantified at the global level

Climate change

We retain the control variables and boundariesoriginally proposedmdashie an atmospheric CO2 con-centration of 350 parts per million (ppm) and anincrease in top-of-atmosphere radiative forcing of+10 W mndash2 relative to preindustrial levels (1)The radiative forcing control variable is the more

inclusive and fundamental although CO2 is im-portant because of its long lifetime in the atmo-sphere and the very large human emissionsHuman-driven changes to radiative forcing in-clude all anthropogenic factors CO2 other green-house gases aerosols and other factors thataffect the energy balance (18) Radiative forcingis generally the more stringent of the two bound-aries although the relationship between it andCO2 can vary through time with changes in therelative importance of the individual radiativeforcing factorsEvidence has accumulated to suggest that the

zone of uncertainty for the CO2 control variableshould be narrowed from 350 to 550 ppm to 350to 450 ppm CO2 (17 18) while retaining the cur-rent zone of uncertainty for radiative forcing of+10 to 15 W mndash2 relative to preindustrial levelsCurrent values of the control variables are 399ppmCO2 (annual average concentration for 2014) (34)and +23Wmndash2 (11 to 33Wmndash2) in 2011 relativeto 1750 (18) Observed changes in climate at cur-rent levels of the control variables confirm theoriginal choice of the boundary values and thenarrowing of the zone of uncertainty for CO2 Forexample there has already been an increase inthe intensity frequency and duration of heatwaves globally (35) the number of heavy rainfall

SCIENCE sciencemagorg 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 1259855-3

Fig 2The subglobal distributions and current status of the control variables for (A) biogeochemical flows of P (B) biogeochemical flows of N (C) land-system change and (D) freshwater use In each panel green areas are within the boundary (safe) yellow areas are within the zone of uncertainty (increasingrisk) and red areas are beyond the zone of uncertainty (high risk) Gray areas in (A) and (B) are areas where P and N fertilizers are not applied in (C) they areareas not covered by major forest biomes and in (D) they are areas where river flow is very low so that environmental flows are not allocated See Table 1 forvalues of the boundaries and their zones of uncertainty and (33) for more details on methods and results

RESEARCH | RESEARCH ARTICLE

1259855-4 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 sciencemagorg SCIENCE

Table 1 The updated control variables and their current values along with the proposed boundaries and zones of uncertainty for all nine planetaryboundaries In the first column the name for the Earth-system process used in the original PB publication (R2009 reference 1) is given for comparison

Earth-systemprocess

Controlvariable(s)

Planetary boundary(zone of uncertainty)

Current value ofcontrol variable

Climatechange(R2009same)

Atmospheric CO2

concentration ppm

Energy imbalanceat top-of-atmosphere W mndash2

350 ppm CO2 (350ndash450 ppm)

+10 W mndash2 (+10ndash15 W mndash2)

3985 ppm CO2

23 W mndash2

(11ndash33 W mndash2)

Change inbiosphereintegrity(R2009Rate ofbiodiversityloss)

Genetic diversityExtinction rate

Functional diversityBiodiversityIntactness Index (BII)

Note These areinterim controlvariables until moreappropriate ones aredeveloped

lt 10 EMSY (10ndash100 EMSY)but with an aspirational goal ofca 1 EMSY (the backgroundrate of extinction loss) EMSY =extinctions per million species-years

Maintain BII at 90 (90ndash30)or above assessedgeographically by biomeslargeregional areas (eg southernAfrica) major marineecosystems (eg coral reefs) orby large functional groups

100ndash1000 EMSY

84 applied tosouthern Africaonly

Stratosphericozonedepletion(R2009 same)

Stratospheric O3

concentration DUlt5 reduction from pre-industrial level of 290 DU(5ndash10) assessed bylatitude

Only transgressedover Antarctica inAustral spring(~200 DU)

Oceanacidification(R2009same)

Carbonate ionconcentrationaverage globalsurface oceansaturation state withrespect to aragonite(Warag)

ge80 of the pre-industrialaragonite saturation state ofmean surface ocean includingnatural diel and seasonalvariability (ge80ndash ge70)

~84 of thepre-industrialaragonitesaturation state

Biogeochemicalflows (P andN cycles)(R2009Biogeochemicalflows (interferencewith P and Ncycles))

P Global P flowfrom freshwatersystems into theocean

P Regional P flowfrom fertilizers toerodible soils

N Global Industrialand intentionalbiological fixationof N

11 Tg P yrndash1 (11ndash100 Tg P yrndash1)

62 Tg yrndash1 mined and applied toerodible (agricultural) soils(62-112 Tg yrndash1) Boundary is aglobal average but regionaldistribution is critical forimpacts

62 Tg N yrndash1 (62ndash82 Tg N yrndash1)Boundary acts as a globallsquovalversquo limiting introduction ofnew reactive N to Earth Systembut regional distribution offertilizer N is critical forimpacts

~22 Tg P yrndash1

~14 Tg P yrndash1

~150 Tg N yrndash1

RESEARCH | RESEARCH ARTICLE

events inmany regions of the world is increasing(17) changes in atmospheric circulation patternshave increased drought in some regions of theworld (17) and the rate of combined mass lossfrom the Greenland and Antarctic ice sheets isincreasing (36)

Changes in biosphere integrity

We propose a two-component approach address-ing two key roles of the biosphere in the Earthsystem The first captures the role of geneticallyunique material as the ldquoinformation bankrdquo thatultimately determines the potential for life to

continue to coevolve with the abiotic componentof the Earth system in the most resilient waypossible Genetic diversity provides the long-termcapacity of the biosphere to persist under andadapt to abrupt and gradual abiotic change Thesecond captures the role of the biosphere inEarth-system functioning through the value rangedistribution and relative abundance of the func-tional traits of the organisms present in an eco-system or biota (7)For the first role the concept of phylogenetic

species variability (PSV) (7 33 37) would be anappropriate control variable However because

global data are not yet available for PSV we re-tain the global extinction rate as an interim con-trol variable although it is measured inaccuratelyand with a time lag There may be a considerablerisk in using extinction rate as a control variablebecause phylogenetic (and functional) diversitymay be more sensitive to human pressures thanspecies-level diversity (38) In principle the bound-ary should be set at a rate of loss of PSV no greaterthan the rate of evolution of new PSV during theHolocene Because that is unknown wemust fallback on the (imperfectly) known extinction rateof well-studied organisms over the past several

SCIENCE sciencemagorg 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 1259855-5

Earth-systemprocess

Controlvariable(s)

Planetary boundary(zone of uncertainty)

Current value ofcontrol variable

Land-systemchange(R2009same)

Global Area offorested land as of original forestcover

Biome Area offorested land as of potential forest

Global 75 (75ndash54) Valuesare a weighted average of thethree individual biomeboundaries and their uncertaintyzones

BiomeTropical 85 (85ndash60)Temperate 50 (50ndash30)Boreal 85 (85ndash60)

62

Freshwateruse(R2009Globalfreshwateruse)

Global Maximumamount ofconsumptive bluewater use (km3yrndash1)

Basin Blue waterwithdrawal as ofmean monthly riverflow

Global 4000 km3 yrndash1

(4000ndash6000 km3 yrndash1)

Basin Maximum monthlywithdrawal as a percentageof mean monthly river flowFor low-flow months 25(25ndash55) for intermediate-flow months 30 (30ndash60)for high-flow months 55(55ndash85)

~2600 km3 yrndash1

Atmosphericaerosolloading(R2009same)

Global AerosolOptical Depth(AOD) but muchregional variation

Regional AOD asa seasonal averageover a region SouthAsian Monsoonused as a case study

Regional (South AsianMonsoon as a case study)anthropogenic total (absorbingand scattering) AOD overIndian subcontinent of 025(025ndash050) absorbing(warming) AOD less than 10of total AOD

030 AOD overSouth Asianregion

Introductionof novel entities(R2009 Chemicalpollution)

No control variablecurrently defined

No boundary currentlyidentified but see boundaryfor stratospheric ozone for anexample of a boundaryrelated to a novel entity (CFCs)

RESEARCH | RESEARCH ARTICLE

million yearsmdashabout 1 per million species-years(39)mdashand add a large uncertainty bound raisingthe boundary to 10 permillion species-years Therisk is that although the Earth system can tol-erate a higher-than-background level of extinc-tions for a time we do not knowwhat levels of ortypes of biodiversity lossmay possibly trigger non-linear or irreversible changes to the Earth systemThe second control variable aims to capture the

role of the biosphere in Earth-system functioningand measures loss of biodiversity components atboth global and biomelarge ecosystem levels Al-though several variables have been developed atlocal scales for measuring functional diversity[eg (40)] finding an appropriate control varia-ble at regional or global levels is challenging Forthe present we propose an interim control var-iable the Biodiversity Intactness Index (BII) (41)BII assesses change in population abundance as aresult of human impacts such as land or resourceuse across a wide range of taxa and functionalgroups at a biome or ecosystem level using pre-industrial era abundance as a reference point Theindex typically ranges from 100 (abundancesacross all functional groups at preindustrial levels)to lower values that reflect the extent and degreeof human modification of populations of plantsand animals BII values for particular functionalgroups can go above 100 if humanmodificationsto ecosystems lead to increases in the abundanceof those speciesDue to a lack of evidence on the relationship

between BII and Earth-system responses we pro-

pose a preliminary boundary at 90 of the BIIbut with a very large uncertainty range (90 to30) that reflects the large gaps in our knowl-edge about the BIIndashEarth-system functioningrelationship (42 43) BII has been so far appliedto southern Africarsquos terrestrial biomes only (seefig S3 for an estimation of aggregated humanpressures on the terrestrial biosphere globally)where the index (not yet disaggregated to func-tional groups) was estimated to be 84 BIIranged from 69 to 91 for the seven countrieswhere it has been applied (41) Observations acrossthese countries suggest that decreases in BII ad-equately capture increasing levels of ecosystemdegradation defined as land uses that do not al-ter the land-cover type but lead to a persistentloss in ecosystem productivity (41)In addition to further work on functional mea-

sures such as BII in the longer term the conceptof biome integritymdashthe functioning and persist-ence of biomes at broad scales (7)mdashoffers a prom-ising approach and with further research couldprovide a set of operational control variables (oneper biome) that is appropriate robust and scien-tifically based

Stratospheric ozone depletion

We retain the original control variable [O3 con-centration in DU (Dobson units)] and boundary(275 DU) This boundary is only transgressedover Antarctica in the austral spring when O3

concentration drops to about 200 DU (44) How-ever the minimum O3 concentration has been

steady for about 15 years and is expected to riseover the coming decades as the ozone hole isrepaired after the phasing out of ozone-depletingsubstances This is an example in which after aboundary has been transgressed regionally hu-manity has taken effective action to return theprocess back to within the boundary

Ocean acidification

This boundary is intimately linked with one ofthe control variables CO2 for the climate changePB The concentration of free H+ ions in the sur-face ocean has increased by about 30 over thepast 200 years due to the increase in atmosphericCO2 (45) This in turn influences carbonate chem-istry in surface ocean waters Specifically it lowersthe saturation state of aragonite (Warag) a form ofcalcium carbonate formed by many marine orga-nisms At Warag lt 1 aragonite will dissolve Nonew evidence has emerged to suggest that theoriginally proposed boundary (ge80 of the pre-industrial average annual global Warag) shouldbe adjusted although geographical heterogeneityin Warag is important in monitoring the state ofthe boundary around the worldrsquos oceans (fig S4)Currently Warag is approximately equal to 84 ofthe preindustrial value (46) This boundary wouldnot be transgressed if the climate-change bound-ary of 350 ppm CO2 were to be respected

Biogeochemical flows

The original boundary was formulated for phos-phorus (P) and nitrogen (N) only but we nowpropose a more generic PB to encompass humaninfluence on biogeochemical flows in general Al-though the carbon cycle is covered in the climate-change boundary other elements such as silicon(47 48) are also important for Earth-system func-tioning Furthermore there is increasing evidencethat ratios between elements in the environmentmay have impacts on biodiversity on land and inthe sea (49ndash51) Thus we may ultimately need todevelop PBs for other elements and their ratiosalthough for now we focus on P and N onlyA two-level approach is now proposed for the

P component of the biogeochemical flows bound-ary (see also the supplementary materials) Theoriginal global-level boundary based on the pre-vention of a large-scale ocean anoxic event isretained with the proposed boundary set at asustained flow of 11 Tg P yearndash1 from freshwatersystems into the ocean Based on the analysis ofCarpenter and Bennett (3) we now propose anadditional regional-level P boundary designedto avert widespread eutrophication of freshwatersystems at a flow of 62 Tg P yearndash1 from fer-tilizers (mined P) to erodible soilsGiven that the addition of P to regional

watersheds is almost entirely from fertilizers theregional-level boundary applies primarily to theworldrsquos croplands The current global rate of ap-plication of P in fertilizers to croplands is 142 TgP yearndash1 (52 53) Observations point toward a fewagricultural regions of very high P applicationrates as the main contributors to the transgres-sion of this boundary (Fig 2 and fig S5A) andsuggest that a redistribution of P from areas

1259855-6 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 sciencemagorg SCIENCE

Fig 3The current status of the control variables for seven of the nine planetary boundaries Thegreen zone is the safe operating space (below the boundary) yellow represents the zone of uncertainty(increasing risk) and red is the high-risk zoneThe planetary boundary itself lies at the inner heavy circleThe control variables have been normalized for the zone of uncertainty (between the two heavy circles)the center of the figure therefore does not represent values of 0 for the control variables The controlvariable shown for climate change is atmospheric CO2 concentration Processes for which global-levelboundaries cannot yet be quantified are represented by gray wedges these are atmospheric aerosolloading novel entities and the functional role of biosphere integrity Modified from (1)

RESEARCH | RESEARCH ARTICLE

where it is currently in excess to areas where thesoil is naturally P-poormay simultaneously boostglobal crop production and reduce the transgres-sion of the regional-level P boundary (3 52 54)The N boundary has been taken from the com-

prehensive analysis of de Vries et al (5) whichproposed a PB for eutrophication of aquatic eco-systems of 62 Tg N yearndash1 from industrial andintentional biological N fixation using the moststringent water quality criterion As for the Pboundary a few agricultural regions of very highN application rates are the main contributors tothe transgression of this boundary (Fig 2 andfig S5B) This suggests that a redistribution of Ncould simultaneously boost global crop produc-tion and reduce the transgression of the regional-level boundaryBecause the major anthropogenic perturba-

tion of both the N and P cycles arises from fertil-izer application we can analyze the links betweenthe independently determined N and P bounda-ries in an integrated way based on the NP ratioin the growing plant tissue of agricultural cropsApplying this ratio which is on average 118 (55)to the P boundary (62 Tg P yearndash1) gives an Nboundary of 73 Tg N yearndash1 Conversely applyingthe ratio to theN boundary (62 TgN yearndash1) givesa P boundary of 53 Tg P yearndash1 The small dif-ferences between the boundaries derived usingthe NP ratio and those calculated independent-ly which are likely nonsignificant differencesgiven the precision of the data available for thecalculations show the internal consistency inour approach to the biogeochemical boundariesMore detail on the development of the P andN

boundaries is given in (33) where we also em-phasize that the proposed P and N boundariesmay be larger for an optimal allocation of N (andP) over the globe

Land-system change

The updated biosphere integrity boundary pro-vides a considerable constraint on the amountand pattern of land-system change in all ter-restrial biomes forests woodlands savannasgrasslands shrublands tundra and so on Theland-system change boundary is now focusedmore tightly on a specific constraint the biogeo-physical processes in land systems that directlyregulate climatemdashexchange of energy water andmomentum between the land surface and theatmosphere The control variable has been changedfrom the amount of cropland to the amount offorest cover remaining as the three major forestbiomesmdashtropical temperate and borealmdashplay astronger role in land surfacendashclimate couplingthan other biomes (56 57) In particular we fo-cus on those land-system changes that can in-fluence the climate in regions beyond the regionwhere the land-system change occurredOf the forest biomes tropical forests have sub-

stantial feedbacks to climate through changes inevapotranspiration when they are converted tononforested systems and changes in the distribu-tion of boreal forests affect the albedo of the landsurface and hence regional energy exchange Bothhave strong regional and global teleconnections

The biome-level boundary for these two types offorest have been set at 85 (Table 1 and thesupplementary materials) and the boundary fortemperate forests has been proposed at 50 ofpotential forest cover because changes to tem-perate forests are estimated to have weaker in-fluences on the climate system at the global levelthan changes to the other two major forestbiomes (56) These boundaries would almostsurely be met if the proposed biosphere integ-rity boundary of 90 BII were respectedEstimates of the current status of the land-

system change boundary are given in Figs 2 and3 and fig S6 and in (58)

Freshwater use

The revised freshwater use boundary has retainedconsumptive use of blue water [from rivers lakesreservoirs and renewable groundwater stores(59)] as the global-level control variable and4000 km3year as the value of the boundaryThis PB may be somewhat higher or lower de-pending on riversrsquo ecological flow requirements(6) Therefore we report here a new assessmentto complement the PB with a basin-scale bound-ary for the maximum rate of blue water with-drawal along rivers based on the amount of waterrequired in the river system to avoid regime shiftsin the functioning of flow-dependent ecosystemsWe base our control variable on the concept ofenvironmental water flows (EWF) which definesthe level of river flows for different hydrologicalcharacteristics of river basins adequate to main-tain a fair-to-good ecosystem state (60ndash62)The variable monthly flow (VMF) method

(33 63) was used to calculate the basin-scaleboundary for water This method takes accountof intra-annual variability by classifying flow re-gimes into high- intermediate- and low-flowmonths and allocating EWF as a percentage ofthe mean monthly flow (MMF) Based on thisanalysis the zones of uncertainty for the river-basin scale water boundary were set at 25 to 55of MMF for the low-flow regime 40 to 70 forthe intermediate-flow regime and 55 to 85 forthe high-flow regime (table S2) The boundarieswere set at the lower end of the uncertaintyranges that encompass average monthly EWFOur new estimates of the current status of thewater use boundarymdashcomputed based on gridcellndashspecific estimates of agricultural industrialand domestic water withdrawalsmdashare shown inFigs 2 and 3 with details in figs S7 and S8

Atmospheric aerosol loading

Aerosols have well-known serious human healtheffects leading to about 72 million deaths peryear (64) They also affect the functioning of theEarth system in many ways (65) (fig S9) Herewe focus on the effect of aerosols on regionalocean-atmosphere circulation as the rationalefor a separate aerosols boundary We adopt aero-sol optical depth (AOD) (33) as the control var-iable and use the south Asian monsoon as a casestudy based on the potential of widespread aero-sol loading over the Indian subcontinent to switchthe monsoon system to a drier state

The background AOD over south Asia is ~015and can be as high as 04 during volcanic events(66) Emissions of black carbon and organic car-bon from cooking and heating with biofuels andfrom diesel transportation and emission of sul-fates and nitrates from fossil fuel combustioncan increase seasonal mean AODs to as high as04 (larger during volcanic periods) leading todecreases of 10 to 15 of incident solar radiationat the surface (fig S9) A substantial decrease inmonsoon activity is likely around an AOD of 050an increase of 035 above the background (67)Taking a precautionary approach toward uncer-tainties surrounding the position of the tippingpoint we propose a boundary at an AOD of 025(an increase due to human activities of 01) witha zone of uncertainty of 025 to 050 The annualmean AOD is currently about 03 (66) within thezone of uncertainty

Introduction of novel entities

We define novel entities as new substances newforms of existing substances and modified lifeforms that have the potential for unwanted geo-physical andor biological effects Anthropogenicintroduction of novel entities to the environmentis of concern at the global level when these en-tities exhibit (i) persistence (ii) mobility acrossscales with consequent widespread distributionsand (iii) potential impacts on vital Earth-systemprocesses or subsystems These potentially in-clude chemicals and other new types of engi-neered materials or organisms [eg (68ndash71)] notpreviously known to the Earth system as well asnaturally occurring elements (for example heavymetals) mobilized by anthropogenic activitiesThe risks associated with the introduction ofnovel entities into the Earth system are exempli-fied by the release of CFCs (chlorofluorocarbons)which are very useful synthetic chemicals thatwere thought to be harmless but had unexpecteddramatic impacts on the stratospheric ozone layerIn effect humanity is repeatedly running suchglobal-scale experiments but not yet applying theinsights from previous experience to new appli-cations (72 73)Today there aremore than 100000 substances

in global commerce (74) If nanomaterials andplastic polymers that degrade to microplasticsare included the list is even longer There is alsoa ldquochemical intensificationrdquo due to the rapidlyincreasing global production of chemicals theexpanding worldwide distribution as chemicalproducts or in consumer goods and the exten-sive global trade in chemical wastes (75)In recent years there has been a growing de-

bate about the global-scale effects of chemicalpollution leading to calls for the definition ofcriteria to identify the kinds of chemical sub-stances that are likely to be globally problematic(76 77) Persson et al (73) proposed that there arethree conditions that need to be fulfilled for achemical to pose a threat to the Earth system (i)the chemical has an unknown disruptive effecton a vital Earth-systemprocess (ii) the disruptiveeffect is not discovered until it is a problem at theglobal scale and (iii) the effect is not readily

SCIENCE sciencemagorg 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 1259855-7

RESEARCH | RESEARCH ARTICLE

reversible The challenge to the research commu-nity is to develop the knowledge base that allowsthe screening of chemicals before they are re-leased into the environment for properties thatmay predispose them toward becoming globalproblemsAs a first step toward meeting this challenge

the three conditions outlined above have beenused as the basis for identifying scenarios ofchemical pollution that fulfill the conditions andas a next step for pinpointing chemical profilesthat fit the scenarios (28) This proposal consti-tutes a first attempt at adding the Earth-systemperspective when assessing hazard and risk ofchemicals and offers a vision for a systematic ap-proach to a complex management situation withmany unknownsDespite this progress in developing an Earth-

systemndashoriented approach there is not yet anaggregate global-level analysis of chemical pol-lution on which to base a control variable or aboundary value It may also serve little purposeto define boundary values and control varia-bles for a planetary boundary of this complexityNevertheless there is a potential threat fromnovel entities to disrupt the functioning of theEarth-system and society needs to learn how tomitigate these unknown risks and manage chem-icals under uncertainty (28 73)Some precautionary and preventive actions

can be considered These may include a strongerfocus on green chemistry (78) finding synergieswith risk-reducing interventions in other fieldssuch as occupational health (79) paying moreattention to learning from earlier mistakes (8081) and investing in science to better under-stand and monitor vital Earth-system processesin order to be able to detect disruptive effectsfrom novel entities as early as possible

Hierarchy of boundaries

An analysis of the many interactions among theboundaries (table S3 and fig S10) suggests thattwo of themmdashclimate change and biosphereintegritymdashare highly integrated emergent system-level phenomena that are connected to all of theother PBs They operate at the level of the wholeEarth system (7) and have coevolved for nearly4 billion years (82) They are regulated by theother boundaries and on the other hand pro-vide the planetary-level overarching systems with-in which the other boundary processes operateFurthermore large changes in the climate or inbiosphere integrity would likely on their ownpush the Earth system out of the Holocene stateIn fact transitions between time periods in Earthhistory have often been delineated by substantialshifts in climate the biosphere or both (82 83)These observations suggest a two-level hierar-

chy of boundaries in which climate change andbiosphere integrity should be recognized as coreplanetary boundaries through which the otherboundaries operate The crossing of one or moreof the other boundaries may seriously affect hu-man well-being and may predispose the trans-gression of a core boundary(ies) but does not byitself lead to a new state of the Earth system This

hierarchical approach to classifying the bounda-ries becomes clearer by examining inmore detailthe roles of climate and biosphere integrity in thefunctioning of the Earth systemThe climate system is a manifestation of the

amount distribution and net balance of energyat Earthrsquos surface The total amount of energysets the overall conditions for life In Earthrsquos cur-rent climate a range of global surface temper-atures and atmospheric pressures allows the threephases of water to be present simultaneouslywith ice and water vapor playing critical roles inthe physical feedbacks of the climate system Thedistribution of energy by latitude over the landand sea surfaces and within the ocean plays amajor role in the circulation of the two greatfluids the ocean and the atmosphere These sys-temic physical characteristics are key spatial de-terminants of the distribution of the biota andthe structure and functioning of ecosystems andare controllers of biogeochemical flowsBiosphere integrity is also crucial to Earth-

system functioning where the biosphere is de-fined as the totality of all ecosystems (terrestrialfreshwater andmarine) on Earth and their biota(32) These ecosystems and biota play a criticalrole in determining the state of the Earth systemregulating its material and energy flows and itsresponses to abrupt and gradual change (7) Di-versity in the biosphere provides resilience toterrestrial and marine ecosystems (83 84) Thebiosphere not only interacts with the other plan-etary boundaries but also increases the capacityof theEarth system topersist in a given state underchanges in these other boundaries The ultimatebasis for the many roles that the biosphere playsin Earth-system dynamics is the genetic code ofthe biota the basic information bank that de-fines the biospherersquos functional role and its ca-pacity to innovate and persist into the future

Planetary boundaries in asocietal context

A proposed approach for sustainable develop-ment goals (SDGs) (85) argues that the stablefunctioning of the Earth system is a prereq-uisite for thriving societies around the world Thisapproach implies that the PB framework orsomething like it will need to be implementedalongside the achievement of targets aimed atmore immediate human needs such as provi-sion of clean affordable and accessible energyand the adequate supply of food World devel-opment within the biophysical limits of a stableEarth system has always been a necessity [eg(86 87)] However only recently for a numberof reasons has it become possible to identifyevaluate and quantify risks of abrupt planetary-and biome-level shifts due to overshoot of keyEarth-system parameters (i) the emergence ofglobal-change thinking and Earth-system think-ing (88) (ii) the rise of ldquothe Planetaryrdquo as a rel-evant level of complex system understanding(89ndash92) and (iii) observable effects of the rapidincrease in human pressures on the planet (16)The PB approach is embedded in this emerg-

ing social context but it does not suggest how to

maneuver within the safe operating space in thequest for global sustainability For example thePB framework does not as yet account for the re-gional distribution of the impact or its histor-ical patterns Nor does the PB framework takeinto account the deeper issues of equity and cau-sation The current levels of the boundary pro-cesses and the transgressions of boundaries thathave already occurred are unevenly caused bydifferent human societies and different socialgroups The wealth benefits that these trans-gressions have brought are also unevenly distrib-uted socially and geographically It is easy toforesee that uneven distribution of causation andbenefits will continue and these differentialsmust surely be addressed for a Holocene-likeEarth-system state to be successfully legitimatedand maintained However the PB framework ascurrently construed provides no guidance as tohow this may be achieved [although some po-tential synergies have been noted (54)] and itcannot readily be used tomake choices betweenpathways for piecemeal maneuvering withinthe safe operating space ormore radical shifts ofglobal governance (93)The nature of the PB framework implies that

two important cautions should be observedwhenapplication of the framework to policy or man-agement is proposed boundary interactions andscale

Boundary interactions

The planetary boundaries framework arises fromthe scientific evidence that Earth is a singlecomplex integrated systemmdashthat is the bound-aries operate as an interdependent set [eg(94)] (table S1 and fig S10) Although a system-atic quantitative analysis of interactions amongall of the processes for which boundaries areproposed remains beyond the scope of currentmodeling and observational capacity the Earthsystem clearly operates in well-defined states inwhich these processes and their interactionscan create stabilizing or destabilizing feedbacks(16 90 95) This has profound implications forglobal sustainability because it emphasizes theneed to address multiple interacting environ-mental processes simultaneously (eg stabilizingthe climate system requires sustainable forestmanagement and stable ocean ecosystems)

Scale

The PB framework is not designed to be ldquodown-scaledrdquo or ldquodisaggregatedrdquo to smaller levels suchas nations or local communities That said thePB framework recognizes the importance ofchanges at the level of subsystems in the Earthsystem (eg biomes or large river basins) on thefunctioning of the Earth system as a whole Alsothere are strong arguments for an integrated ap-proach coupling boundary definitions at region-al and global levels with development goals toenable the application of ldquoPB thinkingrdquo at lev-els (nations basins and regions) where policyaction most commonly occurs [eg (85 96)]This update of the PB framework is one step on

a longer-term evolution of scientific knowledge to

1259855-8 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 sciencemagorg SCIENCE

RESEARCH | RESEARCH ARTICLE

inform and support global sustainability goalsand pathways This evolution is needed morethan ever before there are severe implementa-tion gaps inmany global environmental policiesrelating to the PB issues where problematictrends are not being halted or reversed despiteinternational consensus about the urgency of theproblems The prospect of tighter resource con-straints and rising environmental hazards is alsounavoidably turning the focus onto global socialequity and the planetary stewardship of Earthrsquoslife-support system There is a need for a trulyglobal evidence base with much greater integra-tion among issues in order to respond to theseglobal challenges New research initiatives [egFuture Earth (wwwfutureearthorg)] provide evi-dence that science can respond to this need byapplying Earth-system research to advance a newgeneration of integrated global analyses and toexplore options for transformations toward sus-tainability This is a clear sign that as the risksof the Anthropocene to human well-being be-come clearer research is maturing to a pointwhere a systemic step-change is possiblemdashandnecessarymdashin exploring and defining a safe andjust planetary operating space for the furtherdevelopment of human societies

Methods summary

Our approach to building the planetary bound-aries framework is described above We haveimplemented the framework through an ex-pert assessment and synthesis of the scientificknowledge of intrinsic biophysical processes thatregulate the stability of the Earth system Ourprecautionary approach is based on the main-tenance of a Holocene-like state of the Earthsystem and on an assessment of the level ofhuman-driven change that would risk destabi-lizing this state For the climate change PB thereis already much literature on which to basesuch an assessment For others such as strato-spheric ozone ocean acidification extinctionrates and P andN cycles we have used estimatesof preindustrial values of the control variableas a Holocene baseline Where large undesira-ble thresholds exist and have been studied (egpolar ice sheets Amazon rainforest aragonitedissolution atmospheric aerosols and the southAsian monsoon) quantitative boundaries can bereadily proposed For others where the focus ison erosion of Earth-system resilience the bound-aries are more difficult (but not impossible) toquantify as reflected in larger uncertainty zonesWe used large-scale assessments of the impacts

of human activities on Earth-system functioning[eg Intergovernmental Panel on Climate Change(17 18) the International Geosphere-BiosphereProgramme synthesis (16) and chemicals (75 80)]as sources of community-level understandingon which to propose PBs Our update has alsorelied on post-2009 assessments of individualboundaries by the relevant expert research com-munities examples include phosphorus (3) ni-trogen (5) biosphere integrity (7) freshwater use(5 63) and novel entities [with a focus on chem-icals (28 73)] Finally some new analyses have

been undertaken specifically for this paper (i) afreshwater-use PB based on the EWF approach(33 63) (ii) the linkage of the phosphorus andnitrogen boundaries via the NP ratio in grow-ing crop tissue (33) and (iii) the use of majorforest biomes as the basis for the land-systemchange PB (33)

REFERENCES AND NOTES

1 J Rockstroumlm et al Planetary boundaries Exploring the safeoperating space for humanity Ecol Soc 14 32 (2009)httpwwwecologyandsocietyorgvol14iss2art32

2 J Rockstroumlm et al A safe operating space for humanityNature 461 472ndash475 (2009) doi 101038461472apmid 19779433

3 S R Carpenter E M Bennett Reconsideration of theplanetary boundary for phosphorus Environ Res Lett 6014009 (2011) doi 1010881748-932661014009

4 S W Running Ecology A measurable planetary boundaryfor the biosphere Science 337 1458ndash1459 (2012)doi 101126science1227620 pmid 22997311

5 W de Vries J Kros C Kroeze S P Seitzinger Assessingplanetary and regional nitrogen boundaries related to foodsecurity and adverse environmental impacts Curr OpinionEnviron Sust 5 392ndash402 (2013) doi 101016jcosust201307004

6 D Gerten et al Towards a revised planetary boundary forconsumptive freshwater use Role of environmental flowrequirements Curr Opinion Environ Sust 5 551ndash558 (2013)doi 101016jcosust201311001

7 G M Mace et al Approaches to defining a planetary boundaryfor biodiversity Glob Environ Change 28 289ndash297 (2014)doi 101016jgloenvcha201407009

8 V Galaz Global Environmental Governance Technology andPolitics The Anthropocene Gap (Edward Elgar CheltenhamUK 2014)

9 UN GSP (UN High-Level Panel on Global Sustainability)Resilient People Resilient Planet A Future Worth Choosing(Report for the 2012 Rio+20 Earth Summit United NationsNew York 2012)

10 WBCSD (World Business Council on Sustainable Development)Action 2020 Overview (WBCSD Geneva Switzerlandhttpaction2020org accessed 18 June 2014)

11 R Costanza L Graumlich W Steffen Eds Integrated Historyand Future of People on Earth (MIT Press CambridgeMA USA 2006)

12 S Soumlrlin P Warde in Naturersquos End History and theEnvironment S Soumlrlin P Warde Eds (Palgrave MacMillanLondon 2009) pp 1ndash19

13 R C Bishop Endangered species and uncertainty Theeconomics of a safe minimum standard Am J Agric Econ 6110ndash18 (1978) doi 1023071240156

14 T M Crowards Safe minimum standards Costs andopportunities Ecol Econ 25 303ndash314 (1998) doi 101016S0921-8009(97)00041-4

15 W Steffen J Crutzen J R McNeill The Anthropocene Arehumans now overwhelming the great forces of NatureAmbio 36 614ndash621 (2007) doi 1015790044-7447(2007)36[614TAAHNO]20CO2 pmid 18240674

16 W Steffen et al Global Change and the Earth System A PlanetUnder Pressure (The IGBP Book Series Springer-VerlagBerlin Heidelberg New York 2004)

17 IPCC (Intergovernmental Panel on Climate Change) Managingthe risks of extreme events and disasters to advanceclimate change adaptation A special report of Working GroupsI and II of the IPCC CB Field et al Eds (CambridgeUniversity Press Cambridge UK (2012) doi 101017CBO9781139177245

18 IPCC (Intergovernmental Panel on Climate Change) ClimateChange 2013 The Physical Science Basis Summary forPolicymakers L Alexander et al Eds (IPCC SecretariatGeneva Switzerland 2013) doi 101017CBO9781107415324

19 P J Crutzen Geology of mankind Nature 415 23 (2002)doi 101038415023a pmid 11780095

20 K Richardson W Steffen D Liverman Climate Change GlobalRisks Challenges and Decisions (Cambridge Univ PressCambridge UK 2011)

21 T M Lenton et al Tipping elements in the Earthrsquos climatesystem Proc Natl Acad Sci USA 105 1786ndash1793 (2008)doi 101073pnas0705414105 pmid 18258748

22 M Scheffer et al Early-warning signals for criticaltransitions Nature 461 53ndash59 (2009) doi 101038nature08227 pmid 19727193

23 S R Carpenter W A Brock Rising variance A leadingindicator of ecological transition Ecol Lett 9 311ndash318 (2006)doi 101111j1461-0248200500877x pmid 16958897

24 J Bakke et al Rapid oceanic and atmospheric changes duringthe Younger Dryas cold period Nat Geosci 2 202ndash205(2009) doi 101038ngeo439

25 M Scheffer et al Anticipating critical transitions Science338 344ndash348 (2012) doi 101126science1225244pmid 23087241

26 R Wang et al Flickering gives early warning signals of acritical transition to a eutrophic lake state Nature 492419ndash422 (2012) doi 101038nature11655 pmid 23160492

27 R Biggs S R Carpenter W A Brock Turning back fromthe brink Detecting an impending regime shift in time to avertit Proc Natl Acad Sci USA 106 826ndash831 (2009)doi 101073pnas0811729106 pmid 19124774

28 M MacLeod et al Identifying chemicals that are planetaryboundary threats Environ Sci Technol 48 11057ndash11063(2014) doi 101021es501893m pmid 25181298

29 C S Holling Resilience and stability of ecological systemsAnnu Rev Ecol Syst 4 1ndash23 (1973) doi 101146annureves04110173000245

30 C Folke et al Resilience thinking Integrating resilienceadaptability and transformability Ecol Soc 15 20 (2010)wwwecologyandsocietyorgvol15iss4art20

31 T P Hughes S Carpenter J Rockstroumlm M SchefferB Walker Multiscale regime shifts and planetary boundariesTrends Ecol Evol 28 389ndash395 (2013) doi 101016jtree201305019 pmid 23769417

32 T M Lenton H T P Williams On the origin of planetary-scaletipping points Trends Ecol Evol 28 380ndash382 (2013)doi 101016jtree201306001 pmid 23777818

33 Supplementary text figures and tables are available onScience Online

34 NOAA (National Oceanic and Atmospheric Administration)NOAA-ESRL Annual CO2 Data accessed at httpco2noworgCurrent-CO2CO2-Nowannual-co2html (2014)

35 S E Perkins L V Alexander J Nairn Increasing frequencyintensity and duration of observed global heat waves and warmspells Geophys Res Lett 39 L20714 (2012) doi 1010292012GL053361

36 A Shepherd et al A reconciled estimate of ice-sheet massbalance Science 338 1183ndash1189 (2012) doi 101126science1228102 pmid 23197528

37 M R Helmus T J Bland C K Williams A R IvesPhylogenetic measures of biodiversity Am Nat 169 E68ndashE83(2007) doi 101086511334 pmid 17230400

38 S Drsquoagata et al Human-mediated loss of phylogeneticand functional diversity in coral reef fishes Curr Biol24 555ndash560 (2014) doi 101016jcub201401049pmid 24560574

39 A D Barnosky et al Has the Earthrsquos sixth mass extinctionalready arrived Nature 471 51ndash57 (2011) doi 101038nature09678 pmid 21368823

40 N W Mason F de Bello D Mouillot S Pavoine S Dray Aguide for using functional diversity indices to reveal changesin assembly processes along ecological gradients J VegSci 24 794ndash806 (2013) doi 101111jvs12013

41 R J Scholes R Biggs A biodiversity intactness index Nature434 45ndash49 (2005) doi 101038nature03289pmid 15744293

42 B Cardinale Ecology Impacts of biodiversity loss Science336 552ndash553 (2012) doi 101126science1222102pmid 22556243

43 D U Hooper et al A global synthesis reveals biodiversityloss as a major driver of ecosystem change Nature 486105ndash108 (2012) doi 101038nature11118pmid 22678289

44 BAS (British Antarctic Survey) ldquoAntarctic ozonerdquo wwwantarcticaacukmetjdsozoneindexhtmldata J ShanklinBritish Antarctic Survey (2013)

45 Royal Society Ocean Acidification Due to IncreasingAtmospheric Carbon Dioxide Policy Document 1205 (TheRoyal Society London 2005)

46 J M Guinotte V J Fabry Ocean acidification and its potentialeffects on marine ecosystems Ann N Y Acad Sci 1134320ndash342 (2008) doi 101196annals1439013pmid 18566099

47 D J Conley Terrestrial ecosystems and the globalbiogeochemical silica cycle Global Biogeochem Cycles 16681ndash688 (2002) doi 1010292002GB001894

SCIENCE sciencemagorg 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 1259855-9

RESEARCH | RESEARCH ARTICLE

48 F Vandevenne E Struyf W Clymans P Meire Agriculturalsilica harvest Have humans created a new loop in the globalsilica cycle Front Ecol Environ 10 243ndash248 (2012)doi 101890110046

49 S E Gress T D Nichols C C Northcraft W T PeterjohnNutrient limitation in soils exhibiting differing nitrogenavailabilities What lies beyond nitrogen saturation Ecol 88119ndash130 (2007) doi 1018900012-9658(2007)88[119NLISED]20CO2 pmid 17489460

50 H Hillebrand V Lehmpfuhl Resource stoichiometry andconsumers control the biodiversity-productivity relationship inpelagic metacommunities Am Nat 178 171ndash181 (2011)doi 101086660831 pmid 21750381

51 C M Moore et al Processes and patterns of oceanic nutrientlimitation Nat Geosci 6 701ndash710 (2013) doi 101038ngeo1765

52 G K MacDonald E M Bennett P A Potter N RamankuttyAgronomic phosphorus imbalances across the worldrsquoscroplands Proc Natl Acad Sci USA 108 3086ndash3091 (2011)doi 101073pnas1010808108 pmid 21282605

53 L Bouwman et al Exploring global changes in nitrogen andphosphorus cycles in agriculture induced by livestockproduction over the 1900-2050 period Proc Natl AcadSci USA 110 20882ndash20887 (2013) doi 101073pnas1012878108 pmid 21576477

54 W Steffen M Stafford Smith Planetary boundaries equityand global sustainability Why wealthy countries could benefitfrom more equity Curr Opinion Environ Sust 5 403ndash408(2013) doi 101016jcosust201304007

55 D J Greenwood et al A unifying concept for the dependenceof whole-crop N P ratio on biomass theory and experimentAnn Bot (Lond) 102 967ndash977 (2008) doi 101093aobmcn188 pmid 18840873

56 P K Snyder C Delire J A Foley Evaluating the influence ofdifferent vegetation biomes on the global climate Clim Dyn23 279ndash302 (2004) doi 101007s00382-004-0430-0

57 P C West G T Narisma C C Barford C J KucharikJ A Foley An alternative approach for quantifying climateregulation by ecosystems Front Ecol Environ 9 126ndash133(2010) doi 101890090015

58 EPI (Earth Policy Institute) ldquoForest coverrdquo wwwearthpolicyorgindicatorsC56forests_2012_ (2014)

59 M Falkenmark Meeting water requirements of an expandingworld population Philos Trans R Soc Lond B Biol Sci 352929ndash936 (1997) doi 101098rstb19970072

60 J S Wallace M C Acreman C A Sullivan The sharing ofwater between society and ecosystems From conflict tocatchment-based co-management Philos Trans R Soc LondB Biol Sci 358 2011ndash2026 (2003) doi 101098rstb20031383 pmid 14728795

61 N L Poff et al The natural flow regime A paradigm for riverconservation and restoration BioSci 47 769ndash784 (1997)doi 1023071313099

62 N L Poff J K H Zimmerman Ecological responses to alteredflow regimes A literature review to inform the science andmanagement of environmental flows Biol 55 194ndash205 (2010)doi 101111j1365-2427200902272x

63 A V Pastor F Ludwig H Biemans H Hoff P KabatAccounting for environmental flow requirements in globalwater assessments Hydrol Earth Syst Sci 18 5041ndash5059(2014) doi 105194hess-18-5041-2014

64 WHO (World Health Organization) Burden of Disease from theJoint Effects of Household and Ambient Air Pollution for 2012(wwwwhointphehealth_topicsoutdoorairdatabasesFINAL_HAP_AAP_BoD24March2014pdf accessed 23 June 2014httpwwwwhointphehealth_topicsoutdoorairdatabasesen)

65 O Boucher et al in Climate Change 2013 The Physical ScienceBasis IPCC AR5 WGI report T Stocker et al Eds (CambridgeUniv Press Cambridge UK 2013) chap 7 pp 571ndash657

66 M Chin et al Multi-decadal aerosol variations from 1980 to2009 A perspective from observations and a global modelAtmos Chem Phys 14 3657ndash3690 (2014) doi 105194acp-14-3657-2014

67 V Ramanathan et al Atmospheric brown clouds Impacts onSouth Asian climate and hydrological cycle Proc Natl AcadSci USA 102 5326ndash5333 (2005) doi 101073pnas0500656102 pmid 15749818

68 M Cole P Lindeque C Halsband T S Galloway Microplasticsas contaminants in the marine environment A review MarPollut Bull 62 2588ndash2597 (2011) doi 101016jmarpolbul201109025 pmid 22001295

69 EEA (European Environment Agency) Genetically ModifiedOrganisms (GMOs) The Significance of Gene Flow ThroughPollen Transfer (Environmental Issue Report 28 EuropeanEnvironment Agency Copenhagen Denmark 2002)

70 J A Ivar do Sul M F Costa The present and future ofmicroplastic pollution in the marine environment Environ Pollut185 352ndash364 (2014) doi 101016jenvpol201310036pmid 24275078

71 R Kessler Engineered nanoparticles in consumer productsUnderstanding a new ingredient Environ Health Perspect 119a120ndasha125 (2011) doi 101289ehp119-a120 pmid 21356630

72 M Rees Our Final Century Will Civilisation Survive theTwenty-first Century (Arrow Books London 2003)

73 L M Persson et al Confronting unknown planetary boundarythreats from chemical pollution Environ Sci Technol 4712619ndash12622 (2013) doi 101021es402501c pmid 23980998

74 P P Egeghy et al The exposure data landscape formanufactured chemicals Sci Total Environ 414 159ndash166(2012) doi 101016jscitotenv201110046 pmid 22104386

75 UNEP (United Nations Environment Programme) GCOGlobal Chemicals Outlook Towards Sound Management ofChemicals (United Nations Environment ProgrammeNairobi Kenya 2013)

76 S Strempel M Scheringer C A Ng K HungerbuumlhlerScreening for PBT chemicals among the ldquoexistingrdquo andldquonewrdquo chemicals of the EU Environ Sci Technol 465680ndash5687 (2012) doi 101021es3002713pmid 22494215

77 M Scheringer et al How many persistent organic pollutantsshould we expect Atmos Poll Res 3 383ndash391 (2012)doi 105094APR2012044

78 K Sanderson Chemistry Itrsquos not easy being green Nature469 18ndash20 (2011) doi 101038469018a pmid 21209638

79 P A Schulte et al Occupational safety and health greenchemistry and sustainability A review of areas ofconvergence Environ Health 12 31 (2013) doi 1011861476-069X-12-31 pmid 23587312

80 EEA (European Environment Agency) Late Lessons from EarlyWarnings The Precautionary Principle 1896-2000 (EnvironmentalIssue Report 222001 Copenhagen Denmark 2001)

81 D Gee Late lessons from early warnings Toward realism andprecaution with endocrine-disrupting substances EnvironHealth Perspect 114 (suppl 1) 152ndash160 (2006) doi 101289ehp8134 pmid 16818262

82 T Lenton A Watson A Revolutions That Made the Earth(Oxford Univ Press Oxford UK 2011)

83 R Biggs et al Toward principles for enhancing the resilienceof ecosystem services Annu Rev Environ Resour 37421ndash448 (2012) doi 101146annurev-environ-051211-123836

84 G S Cumming P Olsson F S Chapin III C S HollingResilience experimentation and scale mismatches in social-ecological systems Landscape Ecol 28 1139ndash1150 (2013)doi 101007s10980-012-9725-4

85 D Griggs et al Policy Sustainable development goals forpeople and planet Nature 495 305ndash307 (2013) doi 101038495305a pmid 23518546

86 R Costanza Ed Ecological Economics The Science andManagement of Sustainability (Columbia Univ PressNew York 1991)

87 C Folke in Linking the Natural Environment and the EconomyEssays from the Eco-Eco Group C Folke T Karingberger Eds(Kluwer Academic Publishers Dordrecht Netherlands 1991)pp 77ndash94

88 L Robin S Soumlrlin P Warde Eds The Future of NatureDocuments of Global Change (Yale Univ Press New Haven CT2013)

89 U Heise Sense of Place and Sense of Planet TheEnvironmental Imagination of the Global (Oxford Univ PressOxford 2008)

90 M Scheffer Critical Transitions in Nature and Society(Princeton Univ Press Princeton NJ 2009)

91 J Masco Bad weather On planetary crisis Soc Stud Sci 407ndash40 (2010) doi 1011770306312709341598

92 G Paacutelsson et al Reconceptualizing the lsquoAnthroposrsquo in theAnthropocene Integrating the social sciences and humanitiesin global environmental change research Environ Sci Policy28 4 (2013) doi 101016jenvsci201211004

93 N Castree et al Changing the intellectual climate NatureClim Change 4 763ndash768 (2014) doi 101038nclimate2339

94 J M Anderies S R Carpenter W Steffen J Rockstroumlm Thetopology of non-linear global carbon dynamics From tippingpoints to planetary boundaries Environ Res Lett 8 044048(2013) doi 1010881748-932684044048

95 S E Cornell I C Prentice J I House C J DownyUnderstanding the Earth System Global Change Science forApplication (Cambridge Univ Press Cambridge 2012)

96 J A Dearing et al Safe and just operating spaces for regionalsocial-ecological systems Glob Environ Change 28 227ndash238(2014) doi 101016jgloenvcha201406012

ACKNOWLEDGMENTS

We thank J Foley and N Ramunkutty for contributions to theland-system change boundary A Pastor for analytical work on thePB for freshwater B Armstrong C Butler T McMichael andA Woodward for contributions to the novel entities boundary andB Scholes for comments on an earlier version of the manuscriptData associated with the paper are located at the StockholmResilience Centre Sweden (httpwwwstockholmresilienceorg21researchresearch-programmesplanetary-boundarieshtml)The planetary boundaries research at the Stockholm ResilienceCentre is made possible through a core grant from MISTRA(Swedish Foundation for Strategic Environmental Research) SECis supported by the Swedish Research Council EMB is supportedby the Natural Sciences and Engineering Research Council ofCanada and by the Trottier Institute for Science and Public PolicyRB is supported by a Branco Weiss Fellowship CF is supportedby the Family Erling Persson Academy Programme on GlobalEconomic Dynamics and the Biosphere IF is supported by theStordalen Foundation (Norway) SS is supported by theRiksbanken Jubileumsfond and the Institute for Advanced StudyPrinceton NJ and SRC and VR are supported bythe US National Science Foundation

SUPPLEMENTARY MATERIALS

wwwsciencemagorgcontent34762231259855supplDC1MethodsFigs S1 to S10Tables S1 to S3References (97ndash158)

11 August 2014 accepted 8 January 2015Published online 15 January 2015101126science1259855

1259855-10 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 sciencemagorg SCIENCE

RESEARCH | RESEARCH ARTICLE

DOI 101126science1259855 (2015)347 Science

et alWill SteffenplanetPlanetary boundaries Guiding human development on a changing

This copy is for your personal non-commercial use only

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herefollowing the guidelines

can be obtained byPermission to republish or repurpose articles or portions of articles

) February 12 2015 wwwsciencemagorg (this information is current as of

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httpwwwsciencemagorgcontent34762231259855fullhtmlversion of this article at

including high-resolution figures can be found in the onlineUpdated information and services

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subject collectionsThis article appears in the following

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CopyrightAmerican Association for the Advancement of Science 1200 New York Avenue NW Washington DC 20005 (print ISSN 0036-8075 online ISSN 1095-9203) is published weekly except the last week in December by theScience

on

Feb

ruar

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201

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ence

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org

Dow

nloa

ded

from

RESEARCH ARTICLE

SUSTAINABILITY

Planetary boundaries Guidinghuman development on achanging planetWill Steffen12 Katherine Richardson3 Johan Rockstroumlm1 Sarah E Cornell1

Ingo Fetzer1 Elena M Bennett4 Reinette Biggs15 Stephen R Carpenter6

Wim de Vries78 Cynthia A de Wit9 Carl Folke110 Dieter Gerten11 Jens Heinke111213

Georgina M Mace14 Linn M Persson15 Veerabhadran Ramanathan1617

Belinda Reyers118 Sverker Soumlrlin19

The planetary boundaries framework defines a safe operating space for humanity basedon the intrinsic biophysical processes that regulate the stability of the Earth systemHere we revise and update the planetary boundary framework with a focus on theunderpinning biophysical science based on targeted input from expert researchcommunities and on more general scientific advances over the past 5 years Several of theboundaries now have a two-tier approach reflecting the importance of cross-scaleinteractions and the regional-level heterogeneity of the processes that underpin theboundaries Two core boundariesmdashclimate change and biosphere integritymdashhave beenidentified each of which has the potential on its own to drive the Earth system into a newstate should they be substantially and persistently transgressed

The planetary boundary (PB) approach (1 2)aims to define a safe operating space forhumansocieties to develop and thrive basedon our evolving understanding of the func-tioning and resilience of the Earth system

Since its introduction the framework has beensubject to scientific scrutiny [eg (3ndash7)] and hasattracted considerable interest and discussionswithin the policy governance and business sec-tors as an approach to inform efforts toward glob-al sustainability (8ndash10)In this analysis we further develop the basic

PB framework by (i) introducing a two-tier ap-proach for several of the boundaries to accountfor regional-level heterogeneity (ii) updating thequantification ofmost of the PBs (iii) identifyingtwo core boundaries and (iv) proposing a regional-level quantitative boundary for one of the twothat were not quantified earlier (1)

The basic framework Defininga safe operating space

Throughout history humanity has faced environ-mental constraints at local and regional levelswith some societies dealing with these challengesmore effectively than others (11 12) More recent-ly early industrial societies often used local water-ways and airsheds as dumping grounds for theirwaste and effluent from industrial processes Thiseroded local and regional environmental qualityand stability threatening to undermine the pro-gress made through industrialization by damag-ing human health and degrading ecosystemsEventually this led to the introduction of localor regional boundaries or constraints on what

could be emitted to and extracted from the en-vironment (eg chemicals that pollute airshedsor waterways) and on howmuch the environmentcould be changed by direct human modification(land-usecover change in natural ecosystems)(13) The regulation of some human impacts onthe environmentmdashfor example the introductionof chemical contaminantsmdashis often framed inthe context of ldquosafe limitsrdquo (14)These issues remain but in addition we now

face constraints at the planetary level where themagnitude of the challenge is vastly differentThe humanenterprise has grown so dramaticallysince themid-20th century (15) that the relativelystable 11700-year-long Holocene epoch the onlystate of the planet that we know for certain cansupport contemporary human societies is nowbeing destabilized (figs S1 and S2) (16ndash18) Infact a new geological epoch the Anthropocenehas been proposed (19)The precautionary principle suggests that hu-

man societies would be unwise to drive the Earthsystem substantially away from a Holocene-likecondition A continuing trajectory away from theHolocene could lead with an uncomfortably highprobability to a very different state of the Earthsystem one that is likely to be much less hos-pitable to the development of human societies(17 18 20) The PB framework aims to help guidehuman societies away from such a trajectory bydefining a ldquosafe operating spacerdquo inwhichwe cancontinue to develop and thrive It does this byproposing boundaries for anthropogenic pertur-bation of critical Earth-systemprocesses Respect-ing these boundaries would greatly reduce the

risk that anthropogenic activities could inadver-tently drive the Earth system to a much less hos-pitable stateNine processes each of which is clearly being

modified by human actions were originally sug-gested to form the basis of the PB framework (1)Although these processes are fundamental toEarth-system functioning there are many otherways that Earth-system functioning could be de-scribed including potentially valuable metricsfor quantifying the human imprint on it Thesealternative approaches [eg (4)] often representways to explore and quantify interactions amongthe boundaries They can provide a valuable com-plement to the original approach (1) and furtherenrich the broader PB concept as it continues toevolve

The planetary boundaryframework Thresholds feedbacksresilience uncertainties

A planetary boundary as originally defined (1) isnot equivalent to a global threshold or tippingpoint As Fig 1 shows even when a global- orcontinentalocean basinndashlevel threshold in anEarth-system process is likely to exist [eg (20 21)]the proposed planetary boundary is not placedat the position of the biophysical threshold butrather upstream of itmdashie well before reachingthe threshold This buffer between the boundary(the end of the safe operating space the greenzone in Fig 1) and the threshold not only ac-counts for uncertainty in the precise position ofthe threshold with respect to the control variable

RESEARCH

SCIENCE sciencemagorg 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 1259855-1

1Stockholm Resilience Centre Stockholm University 10691Stockholm Sweden 2Fenner School of Environment andSociety The Australian National University Canberra ACT 2601Australia 3Center for Macroecology Evolution and ClimateUniversity of Copenhagen Natural History Museum of DenmarkUniversitetsparken 15 Building 3 2100 Copenhagen Denmark4Department of Natural Resource Sciences and McGill School ofEnvironment McGill University 21 111 Lakeshore Road Ste-Anne-de-Bellevue QC H9X 3V9 Canada 5Centre for Studies inComplexity Stellenbosch University Private Bag X1Stellenbosch 7602 South Africa 6Center for LimnologyUniversity of Wisconsin 680 North Park Street Madison WI53706 USA 7Alterra Wageningen University and ResearchCentre PO Box 47 6700AA Wageningen Netherlands8Environmental Systems Analysis Group Wageningen UniversityPO Box 47 6700 AA Wageningen Netherlands 9Departmentof Environmental Science and Analytical Chemistry StockholmUniversity 10691 Stockholm Sweden 10Beijer Institute ofEcological Economics Royal Swedish Academy of SciencesSE-10405 Stockholm Sweden 11Research Domain EarthSystem Analysis Potsdam Institute for Climate ImpactResearch (PIK) Telegraphenberg A62 14473 PotsdamGermany 12International Livestock Research Institute POBox 30709 Nairobi 00100 Kenya 13CSIRO (CommonwealthScientific and Industrial Research Organization) St LuciaQLD 4067 Australia 14Centre for Biodiversity andEnvironment Research (CBER) Department of GeneticsEvolution and Environment University College London GowerStreet London WC1E 6BT UK 15Stockholm EnvironmentInstitute Linneacutegatan 87D SE-10451 Stockholm Sweden16Scripps Institution of Oceanography University of Californiaat San Diego 8622 Kennel Way La Jolla CA 92037 USA17TERI (The Energy and Resources Institute) University 10Institutional Area Vasant Kunj New Delhi Delhi 110070India 18Natural Resources and the Environment CSIR POBox 320 Stellenbosch 7599 South Africa 19Division ofHistory of Science Technology and Environment KTH RoyalInstitute of Technology SE-10044 Stockholm SwedenCorresponding author E-mail willsteffenanueduau

but also allows society time to react to early warn-ing signs that it may be approaching a thresh-old and consequent abrupt or risky changeThe developing science of early-warning signs

can warn of an approaching threshold or a de-crease in the capability of a system to persistunder changing conditions Examples includeldquocritical slowing downrdquo in a process (22) in-creasing variance (23) and flickering betweenstates of the system (24ndash26) However for suchscience to be useful in a policy context it mustprovide enough time for society to respond inorder to steer away from an impending thresh-old before it is crossed (27 28) The problem ofsystem inertiamdashfor example in the climate sys-tem (18)mdashneeds to be taken into account in as-sessing the time needed for society to react toearly-warning signsNot all Earth-system processes included in the

PBapproachhave singular thresholds at the globalcontinentalocean basin level (1) Nevertheless itis important that boundaries be established forthese processes They affect the capacity of theEarth system to persist in a Holocene-like stateunder changing conditions (henceforth ldquoresiliencerdquo)by regulating biogeochemical flows (eg the ter-restrial andmarine biological carbon sinks) or byproviding the capacity for ecosystems to tolerateperturbations and shocks and to continue func-tioning under changing abiotic conditions (29 30)Examples of such processes are land-systemchange freshwater use change in biosphere in-tegrity [rate of biodiversity loss in (1 2)] andchanges in other biogeochemical flows in addi-tion to carbon (eg nitrogen and phosphorus)Placing boundaries for these processes is more

difficult than for those with known large-scalethresholds (21) but is nevertheless important formaintaining the resilience of the Earth system asa whole As indicated in Fig 1 these processesmany of which show threshold behavior at localand regional scales can generate feedbacks tothe processes that do have large-scale thresholdsThe classic example is the possible weakening ofnatural carbon sinks which could further de-stabilize the climate system and push it closer tolarge thresholds [eg loss of the Greenland icesheet (18)] An interesting research question ofrelevance to the PB framework is how small-scale regime shifts can propagate across scalesand possibly lead to global-level transitions (31 32)A zone of uncertainty sometimes large is as-

sociatedwith each of the boundaries (yellow zonein Fig 1) This zone encapsulates both gaps andweaknesses in the scientific knowledge base andintrinsic uncertainties in the functioning of theEarth system At the ldquosaferdquo end of the zone of un-certainty current scientific knowledge suggeststhat there is very low probability of crossing acritical threshold or substantially eroding the re-silience of the Earth system Beyond the ldquodangerrdquoend of the zone of uncertainty current knowl-edge suggests a much higher probability of achange to the functioning of the Earth systemthat could potentially be devastating for humansocieties Application of the precautionary prin-ciple dictates that the planetary boundary is setat the ldquosaferdquo end of the zone of uncertainty Thisdoes notmean that transgressing a boundarywillinstantly lead to an unwanted outcome but thatthe farther the boundary is transgressed thehigher the risk of regime shifts destabilized sys-

tem processes or erosion of resilience and thefewer the opportunities to prepare for suchchanges Observations of the climate system showthis principle in action by the influence of in-creasing atmospheric greenhouse gas concentra-tions on the frequency and intensity of manyextreme weather events (17 18)

Linking global and regional scales

PB processes operate across scales from oceanbasinsbiomes or sourcessinks to the level of theEarth system as a whole Here we address thesubglobal aspects of the PB framework Rock-stroumlm et al (1) estimated global boundaries on-ly acknowledging that the control variables formany processes are spatially heterogeneous Thatis changes in control variables at the subgloballevel can influence functioning at the Earth-system level which indicates the need to definesubglobal boundaries that are compatible withthe global-level boundary definition Avoidingthe transgression of subglobal boundaries wouldthus contribute to an aggregate outcome withina planetary-level safe operating spaceWe focus on the five PBs that have strong re-

gional operating scales biosphere integrity biogeo-chemical flows [earlier termed ldquophosphorus (P)andnitrogen (N) cyclesrdquo (12)] land-systemchangefreshwater use and atmospheric aerosol loadingTable S1 describes how transgression of any ofthe proposed boundaries at the subglobal levelaffects the Earth system at the global levelFor those processes where subglobal dynamics

potentially play a critical role in global dynamicsthe operational challenge is to capture the im-portance of subglobal change for the functioning

1259855-2 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 sciencemagorg SCIENCE

Fig 1 The conceptual framework for the planetary boundary approach showing the safe operating space the zone of uncertainty the position ofthe threshold (where one is likely to exist) and the area of high riskModified from (1)

RESEARCH | RESEARCH ARTICLE

of the Earth system To do this we propose thedevelopment of a two-level set of control var-iables and boundaries The subglobal-level unitsof analysis for these six boundaries are notidentical they vary according to the role that theprocesses play in the Earth system (i) changesin biosphere integrity occur at the level of land-based biomes large freshwater ecosystems ormajor marine ecosystems as the largest sub-global unit (ii) the role of direct human-drivenland-system change in biophysical climate regu-lation is primarily related to changes in forestbiomes (iii) freshwater flows and use occur atthe largest subglobal level in the major riverbasins around the world and (iv) changes inbiogeochemical flows exemplified by phospho-rus and nitrogen cycling aggregate from rela-tively localized but very severe perturbationsin intensive agricultural zones to affect globalflows of nutrients We recognize these as crit-ical regions for Earth-system functioningWhereappropriate the updates of the individual bound-aries (see below) (33) now contain both the glob-ally aggregated boundary value of the controlvariable and its regional distribution functionFigure 2 shows the distributions and currentstatus of the control variables for three of theboundaries where subglobal dynamics are crit-

ical biogeochemical cycles land-system changeand freshwater useWe emphasize that our subglobal-level focus is

based on the necessity to consider this level tounderstand the functioning of the Earth systemas awhole The PB framework is thereforemeantto complement not replace or supersede effortsto address local and regional environmental issues

Updates of the individual boundaries

Brief updates of all nine of the PBs are given inthis section and more detailed descriptions ofthe updates for three of the PBs that have under-gone more extensive revision can be found in (33)The geographical distribution issues discussedabove are particularly important for five of thePBs and their control variables and boundarieshave been revised accordingly (Table 1) Figure 3shows the current status of the seven bounda-ries that can be quantified at the global level

Climate change

We retain the control variables and boundariesoriginally proposedmdashie an atmospheric CO2 con-centration of 350 parts per million (ppm) and anincrease in top-of-atmosphere radiative forcing of+10 W mndash2 relative to preindustrial levels (1)The radiative forcing control variable is the more

inclusive and fundamental although CO2 is im-portant because of its long lifetime in the atmo-sphere and the very large human emissionsHuman-driven changes to radiative forcing in-clude all anthropogenic factors CO2 other green-house gases aerosols and other factors thataffect the energy balance (18) Radiative forcingis generally the more stringent of the two bound-aries although the relationship between it andCO2 can vary through time with changes in therelative importance of the individual radiativeforcing factorsEvidence has accumulated to suggest that the

zone of uncertainty for the CO2 control variableshould be narrowed from 350 to 550 ppm to 350to 450 ppm CO2 (17 18) while retaining the cur-rent zone of uncertainty for radiative forcing of+10 to 15 W mndash2 relative to preindustrial levelsCurrent values of the control variables are 399ppmCO2 (annual average concentration for 2014) (34)and +23Wmndash2 (11 to 33Wmndash2) in 2011 relativeto 1750 (18) Observed changes in climate at cur-rent levels of the control variables confirm theoriginal choice of the boundary values and thenarrowing of the zone of uncertainty for CO2 Forexample there has already been an increase inthe intensity frequency and duration of heatwaves globally (35) the number of heavy rainfall

SCIENCE sciencemagorg 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 1259855-3

Fig 2The subglobal distributions and current status of the control variables for (A) biogeochemical flows of P (B) biogeochemical flows of N (C) land-system change and (D) freshwater use In each panel green areas are within the boundary (safe) yellow areas are within the zone of uncertainty (increasingrisk) and red areas are beyond the zone of uncertainty (high risk) Gray areas in (A) and (B) are areas where P and N fertilizers are not applied in (C) they areareas not covered by major forest biomes and in (D) they are areas where river flow is very low so that environmental flows are not allocated See Table 1 forvalues of the boundaries and their zones of uncertainty and (33) for more details on methods and results

RESEARCH | RESEARCH ARTICLE

1259855-4 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 sciencemagorg SCIENCE

Table 1 The updated control variables and their current values along with the proposed boundaries and zones of uncertainty for all nine planetaryboundaries In the first column the name for the Earth-system process used in the original PB publication (R2009 reference 1) is given for comparison

Earth-systemprocess

Controlvariable(s)

Planetary boundary(zone of uncertainty)

Current value ofcontrol variable

Climatechange(R2009same)

Atmospheric CO2

concentration ppm

Energy imbalanceat top-of-atmosphere W mndash2

350 ppm CO2 (350ndash450 ppm)

+10 W mndash2 (+10ndash15 W mndash2)

3985 ppm CO2

23 W mndash2

(11ndash33 W mndash2)

Change inbiosphereintegrity(R2009Rate ofbiodiversityloss)

Genetic diversityExtinction rate

Functional diversityBiodiversityIntactness Index (BII)

Note These areinterim controlvariables until moreappropriate ones aredeveloped

lt 10 EMSY (10ndash100 EMSY)but with an aspirational goal ofca 1 EMSY (the backgroundrate of extinction loss) EMSY =extinctions per million species-years

Maintain BII at 90 (90ndash30)or above assessedgeographically by biomeslargeregional areas (eg southernAfrica) major marineecosystems (eg coral reefs) orby large functional groups

100ndash1000 EMSY

84 applied tosouthern Africaonly

Stratosphericozonedepletion(R2009 same)

Stratospheric O3

concentration DUlt5 reduction from pre-industrial level of 290 DU(5ndash10) assessed bylatitude

Only transgressedover Antarctica inAustral spring(~200 DU)

Oceanacidification(R2009same)

Carbonate ionconcentrationaverage globalsurface oceansaturation state withrespect to aragonite(Warag)

ge80 of the pre-industrialaragonite saturation state ofmean surface ocean includingnatural diel and seasonalvariability (ge80ndash ge70)

~84 of thepre-industrialaragonitesaturation state

Biogeochemicalflows (P andN cycles)(R2009Biogeochemicalflows (interferencewith P and Ncycles))

P Global P flowfrom freshwatersystems into theocean

P Regional P flowfrom fertilizers toerodible soils

N Global Industrialand intentionalbiological fixationof N

11 Tg P yrndash1 (11ndash100 Tg P yrndash1)

62 Tg yrndash1 mined and applied toerodible (agricultural) soils(62-112 Tg yrndash1) Boundary is aglobal average but regionaldistribution is critical forimpacts

62 Tg N yrndash1 (62ndash82 Tg N yrndash1)Boundary acts as a globallsquovalversquo limiting introduction ofnew reactive N to Earth Systembut regional distribution offertilizer N is critical forimpacts

~22 Tg P yrndash1

~14 Tg P yrndash1

~150 Tg N yrndash1

RESEARCH | RESEARCH ARTICLE

events inmany regions of the world is increasing(17) changes in atmospheric circulation patternshave increased drought in some regions of theworld (17) and the rate of combined mass lossfrom the Greenland and Antarctic ice sheets isincreasing (36)

Changes in biosphere integrity

We propose a two-component approach address-ing two key roles of the biosphere in the Earthsystem The first captures the role of geneticallyunique material as the ldquoinformation bankrdquo thatultimately determines the potential for life to

continue to coevolve with the abiotic componentof the Earth system in the most resilient waypossible Genetic diversity provides the long-termcapacity of the biosphere to persist under andadapt to abrupt and gradual abiotic change Thesecond captures the role of the biosphere inEarth-system functioning through the value rangedistribution and relative abundance of the func-tional traits of the organisms present in an eco-system or biota (7)For the first role the concept of phylogenetic

species variability (PSV) (7 33 37) would be anappropriate control variable However because

global data are not yet available for PSV we re-tain the global extinction rate as an interim con-trol variable although it is measured inaccuratelyand with a time lag There may be a considerablerisk in using extinction rate as a control variablebecause phylogenetic (and functional) diversitymay be more sensitive to human pressures thanspecies-level diversity (38) In principle the bound-ary should be set at a rate of loss of PSV no greaterthan the rate of evolution of new PSV during theHolocene Because that is unknown wemust fallback on the (imperfectly) known extinction rateof well-studied organisms over the past several

SCIENCE sciencemagorg 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 1259855-5

Earth-systemprocess

Controlvariable(s)

Planetary boundary(zone of uncertainty)

Current value ofcontrol variable

Land-systemchange(R2009same)

Global Area offorested land as of original forestcover

Biome Area offorested land as of potential forest

Global 75 (75ndash54) Valuesare a weighted average of thethree individual biomeboundaries and their uncertaintyzones

BiomeTropical 85 (85ndash60)Temperate 50 (50ndash30)Boreal 85 (85ndash60)

62

Freshwateruse(R2009Globalfreshwateruse)

Global Maximumamount ofconsumptive bluewater use (km3yrndash1)

Basin Blue waterwithdrawal as ofmean monthly riverflow

Global 4000 km3 yrndash1

(4000ndash6000 km3 yrndash1)

Basin Maximum monthlywithdrawal as a percentageof mean monthly river flowFor low-flow months 25(25ndash55) for intermediate-flow months 30 (30ndash60)for high-flow months 55(55ndash85)

~2600 km3 yrndash1

Atmosphericaerosolloading(R2009same)

Global AerosolOptical Depth(AOD) but muchregional variation

Regional AOD asa seasonal averageover a region SouthAsian Monsoonused as a case study

Regional (South AsianMonsoon as a case study)anthropogenic total (absorbingand scattering) AOD overIndian subcontinent of 025(025ndash050) absorbing(warming) AOD less than 10of total AOD

030 AOD overSouth Asianregion

Introductionof novel entities(R2009 Chemicalpollution)

No control variablecurrently defined

No boundary currentlyidentified but see boundaryfor stratospheric ozone for anexample of a boundaryrelated to a novel entity (CFCs)

RESEARCH | RESEARCH ARTICLE

million yearsmdashabout 1 per million species-years(39)mdashand add a large uncertainty bound raisingthe boundary to 10 permillion species-years Therisk is that although the Earth system can tol-erate a higher-than-background level of extinc-tions for a time we do not knowwhat levels of ortypes of biodiversity lossmay possibly trigger non-linear or irreversible changes to the Earth systemThe second control variable aims to capture the

role of the biosphere in Earth-system functioningand measures loss of biodiversity components atboth global and biomelarge ecosystem levels Al-though several variables have been developed atlocal scales for measuring functional diversity[eg (40)] finding an appropriate control varia-ble at regional or global levels is challenging Forthe present we propose an interim control var-iable the Biodiversity Intactness Index (BII) (41)BII assesses change in population abundance as aresult of human impacts such as land or resourceuse across a wide range of taxa and functionalgroups at a biome or ecosystem level using pre-industrial era abundance as a reference point Theindex typically ranges from 100 (abundancesacross all functional groups at preindustrial levels)to lower values that reflect the extent and degreeof human modification of populations of plantsand animals BII values for particular functionalgroups can go above 100 if humanmodificationsto ecosystems lead to increases in the abundanceof those speciesDue to a lack of evidence on the relationship

between BII and Earth-system responses we pro-

pose a preliminary boundary at 90 of the BIIbut with a very large uncertainty range (90 to30) that reflects the large gaps in our knowl-edge about the BIIndashEarth-system functioningrelationship (42 43) BII has been so far appliedto southern Africarsquos terrestrial biomes only (seefig S3 for an estimation of aggregated humanpressures on the terrestrial biosphere globally)where the index (not yet disaggregated to func-tional groups) was estimated to be 84 BIIranged from 69 to 91 for the seven countrieswhere it has been applied (41) Observations acrossthese countries suggest that decreases in BII ad-equately capture increasing levels of ecosystemdegradation defined as land uses that do not al-ter the land-cover type but lead to a persistentloss in ecosystem productivity (41)In addition to further work on functional mea-

sures such as BII in the longer term the conceptof biome integritymdashthe functioning and persist-ence of biomes at broad scales (7)mdashoffers a prom-ising approach and with further research couldprovide a set of operational control variables (oneper biome) that is appropriate robust and scien-tifically based

Stratospheric ozone depletion

We retain the original control variable [O3 con-centration in DU (Dobson units)] and boundary(275 DU) This boundary is only transgressedover Antarctica in the austral spring when O3

concentration drops to about 200 DU (44) How-ever the minimum O3 concentration has been

steady for about 15 years and is expected to riseover the coming decades as the ozone hole isrepaired after the phasing out of ozone-depletingsubstances This is an example in which after aboundary has been transgressed regionally hu-manity has taken effective action to return theprocess back to within the boundary

Ocean acidification

This boundary is intimately linked with one ofthe control variables CO2 for the climate changePB The concentration of free H+ ions in the sur-face ocean has increased by about 30 over thepast 200 years due to the increase in atmosphericCO2 (45) This in turn influences carbonate chem-istry in surface ocean waters Specifically it lowersthe saturation state of aragonite (Warag) a form ofcalcium carbonate formed by many marine orga-nisms At Warag lt 1 aragonite will dissolve Nonew evidence has emerged to suggest that theoriginally proposed boundary (ge80 of the pre-industrial average annual global Warag) shouldbe adjusted although geographical heterogeneityin Warag is important in monitoring the state ofthe boundary around the worldrsquos oceans (fig S4)Currently Warag is approximately equal to 84 ofthe preindustrial value (46) This boundary wouldnot be transgressed if the climate-change bound-ary of 350 ppm CO2 were to be respected

Biogeochemical flows

The original boundary was formulated for phos-phorus (P) and nitrogen (N) only but we nowpropose a more generic PB to encompass humaninfluence on biogeochemical flows in general Al-though the carbon cycle is covered in the climate-change boundary other elements such as silicon(47 48) are also important for Earth-system func-tioning Furthermore there is increasing evidencethat ratios between elements in the environmentmay have impacts on biodiversity on land and inthe sea (49ndash51) Thus we may ultimately need todevelop PBs for other elements and their ratiosalthough for now we focus on P and N onlyA two-level approach is now proposed for the

P component of the biogeochemical flows bound-ary (see also the supplementary materials) Theoriginal global-level boundary based on the pre-vention of a large-scale ocean anoxic event isretained with the proposed boundary set at asustained flow of 11 Tg P yearndash1 from freshwatersystems into the ocean Based on the analysis ofCarpenter and Bennett (3) we now propose anadditional regional-level P boundary designedto avert widespread eutrophication of freshwatersystems at a flow of 62 Tg P yearndash1 from fer-tilizers (mined P) to erodible soilsGiven that the addition of P to regional

watersheds is almost entirely from fertilizers theregional-level boundary applies primarily to theworldrsquos croplands The current global rate of ap-plication of P in fertilizers to croplands is 142 TgP yearndash1 (52 53) Observations point toward a fewagricultural regions of very high P applicationrates as the main contributors to the transgres-sion of this boundary (Fig 2 and fig S5A) andsuggest that a redistribution of P from areas

1259855-6 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 sciencemagorg SCIENCE

Fig 3The current status of the control variables for seven of the nine planetary boundaries Thegreen zone is the safe operating space (below the boundary) yellow represents the zone of uncertainty(increasing risk) and red is the high-risk zoneThe planetary boundary itself lies at the inner heavy circleThe control variables have been normalized for the zone of uncertainty (between the two heavy circles)the center of the figure therefore does not represent values of 0 for the control variables The controlvariable shown for climate change is atmospheric CO2 concentration Processes for which global-levelboundaries cannot yet be quantified are represented by gray wedges these are atmospheric aerosolloading novel entities and the functional role of biosphere integrity Modified from (1)

RESEARCH | RESEARCH ARTICLE

where it is currently in excess to areas where thesoil is naturally P-poormay simultaneously boostglobal crop production and reduce the transgres-sion of the regional-level P boundary (3 52 54)The N boundary has been taken from the com-

prehensive analysis of de Vries et al (5) whichproposed a PB for eutrophication of aquatic eco-systems of 62 Tg N yearndash1 from industrial andintentional biological N fixation using the moststringent water quality criterion As for the Pboundary a few agricultural regions of very highN application rates are the main contributors tothe transgression of this boundary (Fig 2 andfig S5B) This suggests that a redistribution of Ncould simultaneously boost global crop produc-tion and reduce the transgression of the regional-level boundaryBecause the major anthropogenic perturba-

tion of both the N and P cycles arises from fertil-izer application we can analyze the links betweenthe independently determined N and P bounda-ries in an integrated way based on the NP ratioin the growing plant tissue of agricultural cropsApplying this ratio which is on average 118 (55)to the P boundary (62 Tg P yearndash1) gives an Nboundary of 73 Tg N yearndash1 Conversely applyingthe ratio to theN boundary (62 TgN yearndash1) givesa P boundary of 53 Tg P yearndash1 The small dif-ferences between the boundaries derived usingthe NP ratio and those calculated independent-ly which are likely nonsignificant differencesgiven the precision of the data available for thecalculations show the internal consistency inour approach to the biogeochemical boundariesMore detail on the development of the P andN

boundaries is given in (33) where we also em-phasize that the proposed P and N boundariesmay be larger for an optimal allocation of N (andP) over the globe

Land-system change

The updated biosphere integrity boundary pro-vides a considerable constraint on the amountand pattern of land-system change in all ter-restrial biomes forests woodlands savannasgrasslands shrublands tundra and so on Theland-system change boundary is now focusedmore tightly on a specific constraint the biogeo-physical processes in land systems that directlyregulate climatemdashexchange of energy water andmomentum between the land surface and theatmosphere The control variable has been changedfrom the amount of cropland to the amount offorest cover remaining as the three major forestbiomesmdashtropical temperate and borealmdashplay astronger role in land surfacendashclimate couplingthan other biomes (56 57) In particular we fo-cus on those land-system changes that can in-fluence the climate in regions beyond the regionwhere the land-system change occurredOf the forest biomes tropical forests have sub-

stantial feedbacks to climate through changes inevapotranspiration when they are converted tononforested systems and changes in the distribu-tion of boreal forests affect the albedo of the landsurface and hence regional energy exchange Bothhave strong regional and global teleconnections

The biome-level boundary for these two types offorest have been set at 85 (Table 1 and thesupplementary materials) and the boundary fortemperate forests has been proposed at 50 ofpotential forest cover because changes to tem-perate forests are estimated to have weaker in-fluences on the climate system at the global levelthan changes to the other two major forestbiomes (56) These boundaries would almostsurely be met if the proposed biosphere integ-rity boundary of 90 BII were respectedEstimates of the current status of the land-

system change boundary are given in Figs 2 and3 and fig S6 and in (58)

Freshwater use

The revised freshwater use boundary has retainedconsumptive use of blue water [from rivers lakesreservoirs and renewable groundwater stores(59)] as the global-level control variable and4000 km3year as the value of the boundaryThis PB may be somewhat higher or lower de-pending on riversrsquo ecological flow requirements(6) Therefore we report here a new assessmentto complement the PB with a basin-scale bound-ary for the maximum rate of blue water with-drawal along rivers based on the amount of waterrequired in the river system to avoid regime shiftsin the functioning of flow-dependent ecosystemsWe base our control variable on the concept ofenvironmental water flows (EWF) which definesthe level of river flows for different hydrologicalcharacteristics of river basins adequate to main-tain a fair-to-good ecosystem state (60ndash62)The variable monthly flow (VMF) method

(33 63) was used to calculate the basin-scaleboundary for water This method takes accountof intra-annual variability by classifying flow re-gimes into high- intermediate- and low-flowmonths and allocating EWF as a percentage ofthe mean monthly flow (MMF) Based on thisanalysis the zones of uncertainty for the river-basin scale water boundary were set at 25 to 55of MMF for the low-flow regime 40 to 70 forthe intermediate-flow regime and 55 to 85 forthe high-flow regime (table S2) The boundarieswere set at the lower end of the uncertaintyranges that encompass average monthly EWFOur new estimates of the current status of thewater use boundarymdashcomputed based on gridcellndashspecific estimates of agricultural industrialand domestic water withdrawalsmdashare shown inFigs 2 and 3 with details in figs S7 and S8

Atmospheric aerosol loading

Aerosols have well-known serious human healtheffects leading to about 72 million deaths peryear (64) They also affect the functioning of theEarth system in many ways (65) (fig S9) Herewe focus on the effect of aerosols on regionalocean-atmosphere circulation as the rationalefor a separate aerosols boundary We adopt aero-sol optical depth (AOD) (33) as the control var-iable and use the south Asian monsoon as a casestudy based on the potential of widespread aero-sol loading over the Indian subcontinent to switchthe monsoon system to a drier state

The background AOD over south Asia is ~015and can be as high as 04 during volcanic events(66) Emissions of black carbon and organic car-bon from cooking and heating with biofuels andfrom diesel transportation and emission of sul-fates and nitrates from fossil fuel combustioncan increase seasonal mean AODs to as high as04 (larger during volcanic periods) leading todecreases of 10 to 15 of incident solar radiationat the surface (fig S9) A substantial decrease inmonsoon activity is likely around an AOD of 050an increase of 035 above the background (67)Taking a precautionary approach toward uncer-tainties surrounding the position of the tippingpoint we propose a boundary at an AOD of 025(an increase due to human activities of 01) witha zone of uncertainty of 025 to 050 The annualmean AOD is currently about 03 (66) within thezone of uncertainty

Introduction of novel entities

We define novel entities as new substances newforms of existing substances and modified lifeforms that have the potential for unwanted geo-physical andor biological effects Anthropogenicintroduction of novel entities to the environmentis of concern at the global level when these en-tities exhibit (i) persistence (ii) mobility acrossscales with consequent widespread distributionsand (iii) potential impacts on vital Earth-systemprocesses or subsystems These potentially in-clude chemicals and other new types of engi-neered materials or organisms [eg (68ndash71)] notpreviously known to the Earth system as well asnaturally occurring elements (for example heavymetals) mobilized by anthropogenic activitiesThe risks associated with the introduction ofnovel entities into the Earth system are exempli-fied by the release of CFCs (chlorofluorocarbons)which are very useful synthetic chemicals thatwere thought to be harmless but had unexpecteddramatic impacts on the stratospheric ozone layerIn effect humanity is repeatedly running suchglobal-scale experiments but not yet applying theinsights from previous experience to new appli-cations (72 73)Today there aremore than 100000 substances

in global commerce (74) If nanomaterials andplastic polymers that degrade to microplasticsare included the list is even longer There is alsoa ldquochemical intensificationrdquo due to the rapidlyincreasing global production of chemicals theexpanding worldwide distribution as chemicalproducts or in consumer goods and the exten-sive global trade in chemical wastes (75)In recent years there has been a growing de-

bate about the global-scale effects of chemicalpollution leading to calls for the definition ofcriteria to identify the kinds of chemical sub-stances that are likely to be globally problematic(76 77) Persson et al (73) proposed that there arethree conditions that need to be fulfilled for achemical to pose a threat to the Earth system (i)the chemical has an unknown disruptive effecton a vital Earth-systemprocess (ii) the disruptiveeffect is not discovered until it is a problem at theglobal scale and (iii) the effect is not readily

SCIENCE sciencemagorg 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 1259855-7

RESEARCH | RESEARCH ARTICLE

reversible The challenge to the research commu-nity is to develop the knowledge base that allowsthe screening of chemicals before they are re-leased into the environment for properties thatmay predispose them toward becoming globalproblemsAs a first step toward meeting this challenge

the three conditions outlined above have beenused as the basis for identifying scenarios ofchemical pollution that fulfill the conditions andas a next step for pinpointing chemical profilesthat fit the scenarios (28) This proposal consti-tutes a first attempt at adding the Earth-systemperspective when assessing hazard and risk ofchemicals and offers a vision for a systematic ap-proach to a complex management situation withmany unknownsDespite this progress in developing an Earth-

systemndashoriented approach there is not yet anaggregate global-level analysis of chemical pol-lution on which to base a control variable or aboundary value It may also serve little purposeto define boundary values and control varia-bles for a planetary boundary of this complexityNevertheless there is a potential threat fromnovel entities to disrupt the functioning of theEarth-system and society needs to learn how tomitigate these unknown risks and manage chem-icals under uncertainty (28 73)Some precautionary and preventive actions

can be considered These may include a strongerfocus on green chemistry (78) finding synergieswith risk-reducing interventions in other fieldssuch as occupational health (79) paying moreattention to learning from earlier mistakes (8081) and investing in science to better under-stand and monitor vital Earth-system processesin order to be able to detect disruptive effectsfrom novel entities as early as possible

Hierarchy of boundaries

An analysis of the many interactions among theboundaries (table S3 and fig S10) suggests thattwo of themmdashclimate change and biosphereintegritymdashare highly integrated emergent system-level phenomena that are connected to all of theother PBs They operate at the level of the wholeEarth system (7) and have coevolved for nearly4 billion years (82) They are regulated by theother boundaries and on the other hand pro-vide the planetary-level overarching systems with-in which the other boundary processes operateFurthermore large changes in the climate or inbiosphere integrity would likely on their ownpush the Earth system out of the Holocene stateIn fact transitions between time periods in Earthhistory have often been delineated by substantialshifts in climate the biosphere or both (82 83)These observations suggest a two-level hierar-

chy of boundaries in which climate change andbiosphere integrity should be recognized as coreplanetary boundaries through which the otherboundaries operate The crossing of one or moreof the other boundaries may seriously affect hu-man well-being and may predispose the trans-gression of a core boundary(ies) but does not byitself lead to a new state of the Earth system This

hierarchical approach to classifying the bounda-ries becomes clearer by examining inmore detailthe roles of climate and biosphere integrity in thefunctioning of the Earth systemThe climate system is a manifestation of the

amount distribution and net balance of energyat Earthrsquos surface The total amount of energysets the overall conditions for life In Earthrsquos cur-rent climate a range of global surface temper-atures and atmospheric pressures allows the threephases of water to be present simultaneouslywith ice and water vapor playing critical roles inthe physical feedbacks of the climate system Thedistribution of energy by latitude over the landand sea surfaces and within the ocean plays amajor role in the circulation of the two greatfluids the ocean and the atmosphere These sys-temic physical characteristics are key spatial de-terminants of the distribution of the biota andthe structure and functioning of ecosystems andare controllers of biogeochemical flowsBiosphere integrity is also crucial to Earth-

system functioning where the biosphere is de-fined as the totality of all ecosystems (terrestrialfreshwater andmarine) on Earth and their biota(32) These ecosystems and biota play a criticalrole in determining the state of the Earth systemregulating its material and energy flows and itsresponses to abrupt and gradual change (7) Di-versity in the biosphere provides resilience toterrestrial and marine ecosystems (83 84) Thebiosphere not only interacts with the other plan-etary boundaries but also increases the capacityof theEarth system topersist in a given state underchanges in these other boundaries The ultimatebasis for the many roles that the biosphere playsin Earth-system dynamics is the genetic code ofthe biota the basic information bank that de-fines the biospherersquos functional role and its ca-pacity to innovate and persist into the future

Planetary boundaries in asocietal context

A proposed approach for sustainable develop-ment goals (SDGs) (85) argues that the stablefunctioning of the Earth system is a prereq-uisite for thriving societies around the world Thisapproach implies that the PB framework orsomething like it will need to be implementedalongside the achievement of targets aimed atmore immediate human needs such as provi-sion of clean affordable and accessible energyand the adequate supply of food World devel-opment within the biophysical limits of a stableEarth system has always been a necessity [eg(86 87)] However only recently for a numberof reasons has it become possible to identifyevaluate and quantify risks of abrupt planetary-and biome-level shifts due to overshoot of keyEarth-system parameters (i) the emergence ofglobal-change thinking and Earth-system think-ing (88) (ii) the rise of ldquothe Planetaryrdquo as a rel-evant level of complex system understanding(89ndash92) and (iii) observable effects of the rapidincrease in human pressures on the planet (16)The PB approach is embedded in this emerg-

ing social context but it does not suggest how to

maneuver within the safe operating space in thequest for global sustainability For example thePB framework does not as yet account for the re-gional distribution of the impact or its histor-ical patterns Nor does the PB framework takeinto account the deeper issues of equity and cau-sation The current levels of the boundary pro-cesses and the transgressions of boundaries thathave already occurred are unevenly caused bydifferent human societies and different socialgroups The wealth benefits that these trans-gressions have brought are also unevenly distrib-uted socially and geographically It is easy toforesee that uneven distribution of causation andbenefits will continue and these differentialsmust surely be addressed for a Holocene-likeEarth-system state to be successfully legitimatedand maintained However the PB framework ascurrently construed provides no guidance as tohow this may be achieved [although some po-tential synergies have been noted (54)] and itcannot readily be used tomake choices betweenpathways for piecemeal maneuvering withinthe safe operating space ormore radical shifts ofglobal governance (93)The nature of the PB framework implies that

two important cautions should be observedwhenapplication of the framework to policy or man-agement is proposed boundary interactions andscale

Boundary interactions

The planetary boundaries framework arises fromthe scientific evidence that Earth is a singlecomplex integrated systemmdashthat is the bound-aries operate as an interdependent set [eg(94)] (table S1 and fig S10) Although a system-atic quantitative analysis of interactions amongall of the processes for which boundaries areproposed remains beyond the scope of currentmodeling and observational capacity the Earthsystem clearly operates in well-defined states inwhich these processes and their interactionscan create stabilizing or destabilizing feedbacks(16 90 95) This has profound implications forglobal sustainability because it emphasizes theneed to address multiple interacting environ-mental processes simultaneously (eg stabilizingthe climate system requires sustainable forestmanagement and stable ocean ecosystems)

Scale

The PB framework is not designed to be ldquodown-scaledrdquo or ldquodisaggregatedrdquo to smaller levels suchas nations or local communities That said thePB framework recognizes the importance ofchanges at the level of subsystems in the Earthsystem (eg biomes or large river basins) on thefunctioning of the Earth system as a whole Alsothere are strong arguments for an integrated ap-proach coupling boundary definitions at region-al and global levels with development goals toenable the application of ldquoPB thinkingrdquo at lev-els (nations basins and regions) where policyaction most commonly occurs [eg (85 96)]This update of the PB framework is one step on

a longer-term evolution of scientific knowledge to

1259855-8 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 sciencemagorg SCIENCE

RESEARCH | RESEARCH ARTICLE

inform and support global sustainability goalsand pathways This evolution is needed morethan ever before there are severe implementa-tion gaps inmany global environmental policiesrelating to the PB issues where problematictrends are not being halted or reversed despiteinternational consensus about the urgency of theproblems The prospect of tighter resource con-straints and rising environmental hazards is alsounavoidably turning the focus onto global socialequity and the planetary stewardship of Earthrsquoslife-support system There is a need for a trulyglobal evidence base with much greater integra-tion among issues in order to respond to theseglobal challenges New research initiatives [egFuture Earth (wwwfutureearthorg)] provide evi-dence that science can respond to this need byapplying Earth-system research to advance a newgeneration of integrated global analyses and toexplore options for transformations toward sus-tainability This is a clear sign that as the risksof the Anthropocene to human well-being be-come clearer research is maturing to a pointwhere a systemic step-change is possiblemdashandnecessarymdashin exploring and defining a safe andjust planetary operating space for the furtherdevelopment of human societies

Methods summary

Our approach to building the planetary bound-aries framework is described above We haveimplemented the framework through an ex-pert assessment and synthesis of the scientificknowledge of intrinsic biophysical processes thatregulate the stability of the Earth system Ourprecautionary approach is based on the main-tenance of a Holocene-like state of the Earthsystem and on an assessment of the level ofhuman-driven change that would risk destabi-lizing this state For the climate change PB thereis already much literature on which to basesuch an assessment For others such as strato-spheric ozone ocean acidification extinctionrates and P andN cycles we have used estimatesof preindustrial values of the control variableas a Holocene baseline Where large undesira-ble thresholds exist and have been studied (egpolar ice sheets Amazon rainforest aragonitedissolution atmospheric aerosols and the southAsian monsoon) quantitative boundaries can bereadily proposed For others where the focus ison erosion of Earth-system resilience the bound-aries are more difficult (but not impossible) toquantify as reflected in larger uncertainty zonesWe used large-scale assessments of the impacts

of human activities on Earth-system functioning[eg Intergovernmental Panel on Climate Change(17 18) the International Geosphere-BiosphereProgramme synthesis (16) and chemicals (75 80)]as sources of community-level understandingon which to propose PBs Our update has alsorelied on post-2009 assessments of individualboundaries by the relevant expert research com-munities examples include phosphorus (3) ni-trogen (5) biosphere integrity (7) freshwater use(5 63) and novel entities [with a focus on chem-icals (28 73)] Finally some new analyses have

been undertaken specifically for this paper (i) afreshwater-use PB based on the EWF approach(33 63) (ii) the linkage of the phosphorus andnitrogen boundaries via the NP ratio in grow-ing crop tissue (33) and (iii) the use of majorforest biomes as the basis for the land-systemchange PB (33)

REFERENCES AND NOTES

1 J Rockstroumlm et al Planetary boundaries Exploring the safeoperating space for humanity Ecol Soc 14 32 (2009)httpwwwecologyandsocietyorgvol14iss2art32

2 J Rockstroumlm et al A safe operating space for humanityNature 461 472ndash475 (2009) doi 101038461472apmid 19779433

3 S R Carpenter E M Bennett Reconsideration of theplanetary boundary for phosphorus Environ Res Lett 6014009 (2011) doi 1010881748-932661014009

4 S W Running Ecology A measurable planetary boundaryfor the biosphere Science 337 1458ndash1459 (2012)doi 101126science1227620 pmid 22997311

5 W de Vries J Kros C Kroeze S P Seitzinger Assessingplanetary and regional nitrogen boundaries related to foodsecurity and adverse environmental impacts Curr OpinionEnviron Sust 5 392ndash402 (2013) doi 101016jcosust201307004

6 D Gerten et al Towards a revised planetary boundary forconsumptive freshwater use Role of environmental flowrequirements Curr Opinion Environ Sust 5 551ndash558 (2013)doi 101016jcosust201311001

7 G M Mace et al Approaches to defining a planetary boundaryfor biodiversity Glob Environ Change 28 289ndash297 (2014)doi 101016jgloenvcha201407009

8 V Galaz Global Environmental Governance Technology andPolitics The Anthropocene Gap (Edward Elgar CheltenhamUK 2014)

9 UN GSP (UN High-Level Panel on Global Sustainability)Resilient People Resilient Planet A Future Worth Choosing(Report for the 2012 Rio+20 Earth Summit United NationsNew York 2012)

10 WBCSD (World Business Council on Sustainable Development)Action 2020 Overview (WBCSD Geneva Switzerlandhttpaction2020org accessed 18 June 2014)

11 R Costanza L Graumlich W Steffen Eds Integrated Historyand Future of People on Earth (MIT Press CambridgeMA USA 2006)

12 S Soumlrlin P Warde in Naturersquos End History and theEnvironment S Soumlrlin P Warde Eds (Palgrave MacMillanLondon 2009) pp 1ndash19

13 R C Bishop Endangered species and uncertainty Theeconomics of a safe minimum standard Am J Agric Econ 6110ndash18 (1978) doi 1023071240156

14 T M Crowards Safe minimum standards Costs andopportunities Ecol Econ 25 303ndash314 (1998) doi 101016S0921-8009(97)00041-4

15 W Steffen J Crutzen J R McNeill The Anthropocene Arehumans now overwhelming the great forces of NatureAmbio 36 614ndash621 (2007) doi 1015790044-7447(2007)36[614TAAHNO]20CO2 pmid 18240674

16 W Steffen et al Global Change and the Earth System A PlanetUnder Pressure (The IGBP Book Series Springer-VerlagBerlin Heidelberg New York 2004)

17 IPCC (Intergovernmental Panel on Climate Change) Managingthe risks of extreme events and disasters to advanceclimate change adaptation A special report of Working GroupsI and II of the IPCC CB Field et al Eds (CambridgeUniversity Press Cambridge UK (2012) doi 101017CBO9781139177245

18 IPCC (Intergovernmental Panel on Climate Change) ClimateChange 2013 The Physical Science Basis Summary forPolicymakers L Alexander et al Eds (IPCC SecretariatGeneva Switzerland 2013) doi 101017CBO9781107415324

19 P J Crutzen Geology of mankind Nature 415 23 (2002)doi 101038415023a pmid 11780095

20 K Richardson W Steffen D Liverman Climate Change GlobalRisks Challenges and Decisions (Cambridge Univ PressCambridge UK 2011)

21 T M Lenton et al Tipping elements in the Earthrsquos climatesystem Proc Natl Acad Sci USA 105 1786ndash1793 (2008)doi 101073pnas0705414105 pmid 18258748

22 M Scheffer et al Early-warning signals for criticaltransitions Nature 461 53ndash59 (2009) doi 101038nature08227 pmid 19727193

23 S R Carpenter W A Brock Rising variance A leadingindicator of ecological transition Ecol Lett 9 311ndash318 (2006)doi 101111j1461-0248200500877x pmid 16958897

24 J Bakke et al Rapid oceanic and atmospheric changes duringthe Younger Dryas cold period Nat Geosci 2 202ndash205(2009) doi 101038ngeo439

25 M Scheffer et al Anticipating critical transitions Science338 344ndash348 (2012) doi 101126science1225244pmid 23087241

26 R Wang et al Flickering gives early warning signals of acritical transition to a eutrophic lake state Nature 492419ndash422 (2012) doi 101038nature11655 pmid 23160492

27 R Biggs S R Carpenter W A Brock Turning back fromthe brink Detecting an impending regime shift in time to avertit Proc Natl Acad Sci USA 106 826ndash831 (2009)doi 101073pnas0811729106 pmid 19124774

28 M MacLeod et al Identifying chemicals that are planetaryboundary threats Environ Sci Technol 48 11057ndash11063(2014) doi 101021es501893m pmid 25181298

29 C S Holling Resilience and stability of ecological systemsAnnu Rev Ecol Syst 4 1ndash23 (1973) doi 101146annureves04110173000245

30 C Folke et al Resilience thinking Integrating resilienceadaptability and transformability Ecol Soc 15 20 (2010)wwwecologyandsocietyorgvol15iss4art20

31 T P Hughes S Carpenter J Rockstroumlm M SchefferB Walker Multiscale regime shifts and planetary boundariesTrends Ecol Evol 28 389ndash395 (2013) doi 101016jtree201305019 pmid 23769417

32 T M Lenton H T P Williams On the origin of planetary-scaletipping points Trends Ecol Evol 28 380ndash382 (2013)doi 101016jtree201306001 pmid 23777818

33 Supplementary text figures and tables are available onScience Online

34 NOAA (National Oceanic and Atmospheric Administration)NOAA-ESRL Annual CO2 Data accessed at httpco2noworgCurrent-CO2CO2-Nowannual-co2html (2014)

35 S E Perkins L V Alexander J Nairn Increasing frequencyintensity and duration of observed global heat waves and warmspells Geophys Res Lett 39 L20714 (2012) doi 1010292012GL053361

36 A Shepherd et al A reconciled estimate of ice-sheet massbalance Science 338 1183ndash1189 (2012) doi 101126science1228102 pmid 23197528

37 M R Helmus T J Bland C K Williams A R IvesPhylogenetic measures of biodiversity Am Nat 169 E68ndashE83(2007) doi 101086511334 pmid 17230400

38 S Drsquoagata et al Human-mediated loss of phylogeneticand functional diversity in coral reef fishes Curr Biol24 555ndash560 (2014) doi 101016jcub201401049pmid 24560574

39 A D Barnosky et al Has the Earthrsquos sixth mass extinctionalready arrived Nature 471 51ndash57 (2011) doi 101038nature09678 pmid 21368823

40 N W Mason F de Bello D Mouillot S Pavoine S Dray Aguide for using functional diversity indices to reveal changesin assembly processes along ecological gradients J VegSci 24 794ndash806 (2013) doi 101111jvs12013

41 R J Scholes R Biggs A biodiversity intactness index Nature434 45ndash49 (2005) doi 101038nature03289pmid 15744293

42 B Cardinale Ecology Impacts of biodiversity loss Science336 552ndash553 (2012) doi 101126science1222102pmid 22556243

43 D U Hooper et al A global synthesis reveals biodiversityloss as a major driver of ecosystem change Nature 486105ndash108 (2012) doi 101038nature11118pmid 22678289

44 BAS (British Antarctic Survey) ldquoAntarctic ozonerdquo wwwantarcticaacukmetjdsozoneindexhtmldata J ShanklinBritish Antarctic Survey (2013)

45 Royal Society Ocean Acidification Due to IncreasingAtmospheric Carbon Dioxide Policy Document 1205 (TheRoyal Society London 2005)

46 J M Guinotte V J Fabry Ocean acidification and its potentialeffects on marine ecosystems Ann N Y Acad Sci 1134320ndash342 (2008) doi 101196annals1439013pmid 18566099

47 D J Conley Terrestrial ecosystems and the globalbiogeochemical silica cycle Global Biogeochem Cycles 16681ndash688 (2002) doi 1010292002GB001894

SCIENCE sciencemagorg 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 1259855-9

RESEARCH | RESEARCH ARTICLE

48 F Vandevenne E Struyf W Clymans P Meire Agriculturalsilica harvest Have humans created a new loop in the globalsilica cycle Front Ecol Environ 10 243ndash248 (2012)doi 101890110046

49 S E Gress T D Nichols C C Northcraft W T PeterjohnNutrient limitation in soils exhibiting differing nitrogenavailabilities What lies beyond nitrogen saturation Ecol 88119ndash130 (2007) doi 1018900012-9658(2007)88[119NLISED]20CO2 pmid 17489460

50 H Hillebrand V Lehmpfuhl Resource stoichiometry andconsumers control the biodiversity-productivity relationship inpelagic metacommunities Am Nat 178 171ndash181 (2011)doi 101086660831 pmid 21750381

51 C M Moore et al Processes and patterns of oceanic nutrientlimitation Nat Geosci 6 701ndash710 (2013) doi 101038ngeo1765

52 G K MacDonald E M Bennett P A Potter N RamankuttyAgronomic phosphorus imbalances across the worldrsquoscroplands Proc Natl Acad Sci USA 108 3086ndash3091 (2011)doi 101073pnas1010808108 pmid 21282605

53 L Bouwman et al Exploring global changes in nitrogen andphosphorus cycles in agriculture induced by livestockproduction over the 1900-2050 period Proc Natl AcadSci USA 110 20882ndash20887 (2013) doi 101073pnas1012878108 pmid 21576477

54 W Steffen M Stafford Smith Planetary boundaries equityand global sustainability Why wealthy countries could benefitfrom more equity Curr Opinion Environ Sust 5 403ndash408(2013) doi 101016jcosust201304007

55 D J Greenwood et al A unifying concept for the dependenceof whole-crop N P ratio on biomass theory and experimentAnn Bot (Lond) 102 967ndash977 (2008) doi 101093aobmcn188 pmid 18840873

56 P K Snyder C Delire J A Foley Evaluating the influence ofdifferent vegetation biomes on the global climate Clim Dyn23 279ndash302 (2004) doi 101007s00382-004-0430-0

57 P C West G T Narisma C C Barford C J KucharikJ A Foley An alternative approach for quantifying climateregulation by ecosystems Front Ecol Environ 9 126ndash133(2010) doi 101890090015

58 EPI (Earth Policy Institute) ldquoForest coverrdquo wwwearthpolicyorgindicatorsC56forests_2012_ (2014)

59 M Falkenmark Meeting water requirements of an expandingworld population Philos Trans R Soc Lond B Biol Sci 352929ndash936 (1997) doi 101098rstb19970072

60 J S Wallace M C Acreman C A Sullivan The sharing ofwater between society and ecosystems From conflict tocatchment-based co-management Philos Trans R Soc LondB Biol Sci 358 2011ndash2026 (2003) doi 101098rstb20031383 pmid 14728795

61 N L Poff et al The natural flow regime A paradigm for riverconservation and restoration BioSci 47 769ndash784 (1997)doi 1023071313099

62 N L Poff J K H Zimmerman Ecological responses to alteredflow regimes A literature review to inform the science andmanagement of environmental flows Biol 55 194ndash205 (2010)doi 101111j1365-2427200902272x

63 A V Pastor F Ludwig H Biemans H Hoff P KabatAccounting for environmental flow requirements in globalwater assessments Hydrol Earth Syst Sci 18 5041ndash5059(2014) doi 105194hess-18-5041-2014

64 WHO (World Health Organization) Burden of Disease from theJoint Effects of Household and Ambient Air Pollution for 2012(wwwwhointphehealth_topicsoutdoorairdatabasesFINAL_HAP_AAP_BoD24March2014pdf accessed 23 June 2014httpwwwwhointphehealth_topicsoutdoorairdatabasesen)

65 O Boucher et al in Climate Change 2013 The Physical ScienceBasis IPCC AR5 WGI report T Stocker et al Eds (CambridgeUniv Press Cambridge UK 2013) chap 7 pp 571ndash657

66 M Chin et al Multi-decadal aerosol variations from 1980 to2009 A perspective from observations and a global modelAtmos Chem Phys 14 3657ndash3690 (2014) doi 105194acp-14-3657-2014

67 V Ramanathan et al Atmospheric brown clouds Impacts onSouth Asian climate and hydrological cycle Proc Natl AcadSci USA 102 5326ndash5333 (2005) doi 101073pnas0500656102 pmid 15749818

68 M Cole P Lindeque C Halsband T S Galloway Microplasticsas contaminants in the marine environment A review MarPollut Bull 62 2588ndash2597 (2011) doi 101016jmarpolbul201109025 pmid 22001295

69 EEA (European Environment Agency) Genetically ModifiedOrganisms (GMOs) The Significance of Gene Flow ThroughPollen Transfer (Environmental Issue Report 28 EuropeanEnvironment Agency Copenhagen Denmark 2002)

70 J A Ivar do Sul M F Costa The present and future ofmicroplastic pollution in the marine environment Environ Pollut185 352ndash364 (2014) doi 101016jenvpol201310036pmid 24275078

71 R Kessler Engineered nanoparticles in consumer productsUnderstanding a new ingredient Environ Health Perspect 119a120ndasha125 (2011) doi 101289ehp119-a120 pmid 21356630

72 M Rees Our Final Century Will Civilisation Survive theTwenty-first Century (Arrow Books London 2003)

73 L M Persson et al Confronting unknown planetary boundarythreats from chemical pollution Environ Sci Technol 4712619ndash12622 (2013) doi 101021es402501c pmid 23980998

74 P P Egeghy et al The exposure data landscape formanufactured chemicals Sci Total Environ 414 159ndash166(2012) doi 101016jscitotenv201110046 pmid 22104386

75 UNEP (United Nations Environment Programme) GCOGlobal Chemicals Outlook Towards Sound Management ofChemicals (United Nations Environment ProgrammeNairobi Kenya 2013)

76 S Strempel M Scheringer C A Ng K HungerbuumlhlerScreening for PBT chemicals among the ldquoexistingrdquo andldquonewrdquo chemicals of the EU Environ Sci Technol 465680ndash5687 (2012) doi 101021es3002713pmid 22494215

77 M Scheringer et al How many persistent organic pollutantsshould we expect Atmos Poll Res 3 383ndash391 (2012)doi 105094APR2012044

78 K Sanderson Chemistry Itrsquos not easy being green Nature469 18ndash20 (2011) doi 101038469018a pmid 21209638

79 P A Schulte et al Occupational safety and health greenchemistry and sustainability A review of areas ofconvergence Environ Health 12 31 (2013) doi 1011861476-069X-12-31 pmid 23587312

80 EEA (European Environment Agency) Late Lessons from EarlyWarnings The Precautionary Principle 1896-2000 (EnvironmentalIssue Report 222001 Copenhagen Denmark 2001)

81 D Gee Late lessons from early warnings Toward realism andprecaution with endocrine-disrupting substances EnvironHealth Perspect 114 (suppl 1) 152ndash160 (2006) doi 101289ehp8134 pmid 16818262

82 T Lenton A Watson A Revolutions That Made the Earth(Oxford Univ Press Oxford UK 2011)

83 R Biggs et al Toward principles for enhancing the resilienceof ecosystem services Annu Rev Environ Resour 37421ndash448 (2012) doi 101146annurev-environ-051211-123836

84 G S Cumming P Olsson F S Chapin III C S HollingResilience experimentation and scale mismatches in social-ecological systems Landscape Ecol 28 1139ndash1150 (2013)doi 101007s10980-012-9725-4

85 D Griggs et al Policy Sustainable development goals forpeople and planet Nature 495 305ndash307 (2013) doi 101038495305a pmid 23518546

86 R Costanza Ed Ecological Economics The Science andManagement of Sustainability (Columbia Univ PressNew York 1991)

87 C Folke in Linking the Natural Environment and the EconomyEssays from the Eco-Eco Group C Folke T Karingberger Eds(Kluwer Academic Publishers Dordrecht Netherlands 1991)pp 77ndash94

88 L Robin S Soumlrlin P Warde Eds The Future of NatureDocuments of Global Change (Yale Univ Press New Haven CT2013)

89 U Heise Sense of Place and Sense of Planet TheEnvironmental Imagination of the Global (Oxford Univ PressOxford 2008)

90 M Scheffer Critical Transitions in Nature and Society(Princeton Univ Press Princeton NJ 2009)

91 J Masco Bad weather On planetary crisis Soc Stud Sci 407ndash40 (2010) doi 1011770306312709341598

92 G Paacutelsson et al Reconceptualizing the lsquoAnthroposrsquo in theAnthropocene Integrating the social sciences and humanitiesin global environmental change research Environ Sci Policy28 4 (2013) doi 101016jenvsci201211004

93 N Castree et al Changing the intellectual climate NatureClim Change 4 763ndash768 (2014) doi 101038nclimate2339

94 J M Anderies S R Carpenter W Steffen J Rockstroumlm Thetopology of non-linear global carbon dynamics From tippingpoints to planetary boundaries Environ Res Lett 8 044048(2013) doi 1010881748-932684044048

95 S E Cornell I C Prentice J I House C J DownyUnderstanding the Earth System Global Change Science forApplication (Cambridge Univ Press Cambridge 2012)

96 J A Dearing et al Safe and just operating spaces for regionalsocial-ecological systems Glob Environ Change 28 227ndash238(2014) doi 101016jgloenvcha201406012

ACKNOWLEDGMENTS

We thank J Foley and N Ramunkutty for contributions to theland-system change boundary A Pastor for analytical work on thePB for freshwater B Armstrong C Butler T McMichael andA Woodward for contributions to the novel entities boundary andB Scholes for comments on an earlier version of the manuscriptData associated with the paper are located at the StockholmResilience Centre Sweden (httpwwwstockholmresilienceorg21researchresearch-programmesplanetary-boundarieshtml)The planetary boundaries research at the Stockholm ResilienceCentre is made possible through a core grant from MISTRA(Swedish Foundation for Strategic Environmental Research) SECis supported by the Swedish Research Council EMB is supportedby the Natural Sciences and Engineering Research Council ofCanada and by the Trottier Institute for Science and Public PolicyRB is supported by a Branco Weiss Fellowship CF is supportedby the Family Erling Persson Academy Programme on GlobalEconomic Dynamics and the Biosphere IF is supported by theStordalen Foundation (Norway) SS is supported by theRiksbanken Jubileumsfond and the Institute for Advanced StudyPrinceton NJ and SRC and VR are supported bythe US National Science Foundation

SUPPLEMENTARY MATERIALS

wwwsciencemagorgcontent34762231259855supplDC1MethodsFigs S1 to S10Tables S1 to S3References (97ndash158)

11 August 2014 accepted 8 January 2015Published online 15 January 2015101126science1259855

1259855-10 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 sciencemagorg SCIENCE

RESEARCH | RESEARCH ARTICLE

DOI 101126science1259855 (2015)347 Science

et alWill SteffenplanetPlanetary boundaries Guiding human development on a changing

This copy is for your personal non-commercial use only

clicking herecolleagues clients or customers by you can order high-quality copies for yourIf you wish to distribute this article to others

herefollowing the guidelines

can be obtained byPermission to republish or repurpose articles or portions of articles

) February 12 2015 wwwsciencemagorg (this information is current as of

The following resources related to this article are available online at

httpwwwsciencemagorgcontent34762231259855fullhtmlversion of this article at

including high-resolution figures can be found in the onlineUpdated information and services

httpwwwsciencemagorgcontentsuppl20150114science1259855DC1html can be found at Supporting Online Material

httpwwwsciencemagorgcontent34762231259855fullhtmlrelatedfound at

can berelated to this article A list of selected additional articles on the Science Web sites

httpwwwsciencemagorgcontent34762231259855fullhtmlref-list-1 27 of which can be accessed freecites 120 articlesThis article

httpwwwsciencemagorgcgicollectionecologyEcology

subject collectionsThis article appears in the following

registered trademark of AAAS is aScience2015 by the American Association for the Advancement of Science all rights reserved The title

CopyrightAmerican Association for the Advancement of Science 1200 New York Avenue NW Washington DC 20005 (print ISSN 0036-8075 online ISSN 1095-9203) is published weekly except the last week in December by theScience

on

Feb

ruar

y 13

201

5w

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ence

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org

Dow

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ded

from

but also allows society time to react to early warn-ing signs that it may be approaching a thresh-old and consequent abrupt or risky changeThe developing science of early-warning signs

can warn of an approaching threshold or a de-crease in the capability of a system to persistunder changing conditions Examples includeldquocritical slowing downrdquo in a process (22) in-creasing variance (23) and flickering betweenstates of the system (24ndash26) However for suchscience to be useful in a policy context it mustprovide enough time for society to respond inorder to steer away from an impending thresh-old before it is crossed (27 28) The problem ofsystem inertiamdashfor example in the climate sys-tem (18)mdashneeds to be taken into account in as-sessing the time needed for society to react toearly-warning signsNot all Earth-system processes included in the

PBapproachhave singular thresholds at the globalcontinentalocean basin level (1) Nevertheless itis important that boundaries be established forthese processes They affect the capacity of theEarth system to persist in a Holocene-like stateunder changing conditions (henceforth ldquoresiliencerdquo)by regulating biogeochemical flows (eg the ter-restrial andmarine biological carbon sinks) or byproviding the capacity for ecosystems to tolerateperturbations and shocks and to continue func-tioning under changing abiotic conditions (29 30)Examples of such processes are land-systemchange freshwater use change in biosphere in-tegrity [rate of biodiversity loss in (1 2)] andchanges in other biogeochemical flows in addi-tion to carbon (eg nitrogen and phosphorus)Placing boundaries for these processes is more

difficult than for those with known large-scalethresholds (21) but is nevertheless important formaintaining the resilience of the Earth system asa whole As indicated in Fig 1 these processesmany of which show threshold behavior at localand regional scales can generate feedbacks tothe processes that do have large-scale thresholdsThe classic example is the possible weakening ofnatural carbon sinks which could further de-stabilize the climate system and push it closer tolarge thresholds [eg loss of the Greenland icesheet (18)] An interesting research question ofrelevance to the PB framework is how small-scale regime shifts can propagate across scalesand possibly lead to global-level transitions (31 32)A zone of uncertainty sometimes large is as-

sociatedwith each of the boundaries (yellow zonein Fig 1) This zone encapsulates both gaps andweaknesses in the scientific knowledge base andintrinsic uncertainties in the functioning of theEarth system At the ldquosaferdquo end of the zone of un-certainty current scientific knowledge suggeststhat there is very low probability of crossing acritical threshold or substantially eroding the re-silience of the Earth system Beyond the ldquodangerrdquoend of the zone of uncertainty current knowl-edge suggests a much higher probability of achange to the functioning of the Earth systemthat could potentially be devastating for humansocieties Application of the precautionary prin-ciple dictates that the planetary boundary is setat the ldquosaferdquo end of the zone of uncertainty Thisdoes notmean that transgressing a boundarywillinstantly lead to an unwanted outcome but thatthe farther the boundary is transgressed thehigher the risk of regime shifts destabilized sys-

tem processes or erosion of resilience and thefewer the opportunities to prepare for suchchanges Observations of the climate system showthis principle in action by the influence of in-creasing atmospheric greenhouse gas concentra-tions on the frequency and intensity of manyextreme weather events (17 18)

Linking global and regional scales

PB processes operate across scales from oceanbasinsbiomes or sourcessinks to the level of theEarth system as a whole Here we address thesubglobal aspects of the PB framework Rock-stroumlm et al (1) estimated global boundaries on-ly acknowledging that the control variables formany processes are spatially heterogeneous Thatis changes in control variables at the subgloballevel can influence functioning at the Earth-system level which indicates the need to definesubglobal boundaries that are compatible withthe global-level boundary definition Avoidingthe transgression of subglobal boundaries wouldthus contribute to an aggregate outcome withina planetary-level safe operating spaceWe focus on the five PBs that have strong re-

gional operating scales biosphere integrity biogeo-chemical flows [earlier termed ldquophosphorus (P)andnitrogen (N) cyclesrdquo (12)] land-systemchangefreshwater use and atmospheric aerosol loadingTable S1 describes how transgression of any ofthe proposed boundaries at the subglobal levelaffects the Earth system at the global levelFor those processes where subglobal dynamics

potentially play a critical role in global dynamicsthe operational challenge is to capture the im-portance of subglobal change for the functioning

1259855-2 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 sciencemagorg SCIENCE

Fig 1 The conceptual framework for the planetary boundary approach showing the safe operating space the zone of uncertainty the position ofthe threshold (where one is likely to exist) and the area of high riskModified from (1)

RESEARCH | RESEARCH ARTICLE

of the Earth system To do this we propose thedevelopment of a two-level set of control var-iables and boundaries The subglobal-level unitsof analysis for these six boundaries are notidentical they vary according to the role that theprocesses play in the Earth system (i) changesin biosphere integrity occur at the level of land-based biomes large freshwater ecosystems ormajor marine ecosystems as the largest sub-global unit (ii) the role of direct human-drivenland-system change in biophysical climate regu-lation is primarily related to changes in forestbiomes (iii) freshwater flows and use occur atthe largest subglobal level in the major riverbasins around the world and (iv) changes inbiogeochemical flows exemplified by phospho-rus and nitrogen cycling aggregate from rela-tively localized but very severe perturbationsin intensive agricultural zones to affect globalflows of nutrients We recognize these as crit-ical regions for Earth-system functioningWhereappropriate the updates of the individual bound-aries (see below) (33) now contain both the glob-ally aggregated boundary value of the controlvariable and its regional distribution functionFigure 2 shows the distributions and currentstatus of the control variables for three of theboundaries where subglobal dynamics are crit-

ical biogeochemical cycles land-system changeand freshwater useWe emphasize that our subglobal-level focus is

based on the necessity to consider this level tounderstand the functioning of the Earth systemas awhole The PB framework is thereforemeantto complement not replace or supersede effortsto address local and regional environmental issues

Updates of the individual boundaries

Brief updates of all nine of the PBs are given inthis section and more detailed descriptions ofthe updates for three of the PBs that have under-gone more extensive revision can be found in (33)The geographical distribution issues discussedabove are particularly important for five of thePBs and their control variables and boundarieshave been revised accordingly (Table 1) Figure 3shows the current status of the seven bounda-ries that can be quantified at the global level

Climate change

We retain the control variables and boundariesoriginally proposedmdashie an atmospheric CO2 con-centration of 350 parts per million (ppm) and anincrease in top-of-atmosphere radiative forcing of+10 W mndash2 relative to preindustrial levels (1)The radiative forcing control variable is the more

inclusive and fundamental although CO2 is im-portant because of its long lifetime in the atmo-sphere and the very large human emissionsHuman-driven changes to radiative forcing in-clude all anthropogenic factors CO2 other green-house gases aerosols and other factors thataffect the energy balance (18) Radiative forcingis generally the more stringent of the two bound-aries although the relationship between it andCO2 can vary through time with changes in therelative importance of the individual radiativeforcing factorsEvidence has accumulated to suggest that the

zone of uncertainty for the CO2 control variableshould be narrowed from 350 to 550 ppm to 350to 450 ppm CO2 (17 18) while retaining the cur-rent zone of uncertainty for radiative forcing of+10 to 15 W mndash2 relative to preindustrial levelsCurrent values of the control variables are 399ppmCO2 (annual average concentration for 2014) (34)and +23Wmndash2 (11 to 33Wmndash2) in 2011 relativeto 1750 (18) Observed changes in climate at cur-rent levels of the control variables confirm theoriginal choice of the boundary values and thenarrowing of the zone of uncertainty for CO2 Forexample there has already been an increase inthe intensity frequency and duration of heatwaves globally (35) the number of heavy rainfall

SCIENCE sciencemagorg 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 1259855-3

Fig 2The subglobal distributions and current status of the control variables for (A) biogeochemical flows of P (B) biogeochemical flows of N (C) land-system change and (D) freshwater use In each panel green areas are within the boundary (safe) yellow areas are within the zone of uncertainty (increasingrisk) and red areas are beyond the zone of uncertainty (high risk) Gray areas in (A) and (B) are areas where P and N fertilizers are not applied in (C) they areareas not covered by major forest biomes and in (D) they are areas where river flow is very low so that environmental flows are not allocated See Table 1 forvalues of the boundaries and their zones of uncertainty and (33) for more details on methods and results

RESEARCH | RESEARCH ARTICLE

1259855-4 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 sciencemagorg SCIENCE

Table 1 The updated control variables and their current values along with the proposed boundaries and zones of uncertainty for all nine planetaryboundaries In the first column the name for the Earth-system process used in the original PB publication (R2009 reference 1) is given for comparison

Earth-systemprocess

Controlvariable(s)

Planetary boundary(zone of uncertainty)

Current value ofcontrol variable

Climatechange(R2009same)

Atmospheric CO2

concentration ppm

Energy imbalanceat top-of-atmosphere W mndash2

350 ppm CO2 (350ndash450 ppm)

+10 W mndash2 (+10ndash15 W mndash2)

3985 ppm CO2

23 W mndash2

(11ndash33 W mndash2)

Change inbiosphereintegrity(R2009Rate ofbiodiversityloss)

Genetic diversityExtinction rate

Functional diversityBiodiversityIntactness Index (BII)

Note These areinterim controlvariables until moreappropriate ones aredeveloped

lt 10 EMSY (10ndash100 EMSY)but with an aspirational goal ofca 1 EMSY (the backgroundrate of extinction loss) EMSY =extinctions per million species-years

Maintain BII at 90 (90ndash30)or above assessedgeographically by biomeslargeregional areas (eg southernAfrica) major marineecosystems (eg coral reefs) orby large functional groups

100ndash1000 EMSY

84 applied tosouthern Africaonly

Stratosphericozonedepletion(R2009 same)

Stratospheric O3

concentration DUlt5 reduction from pre-industrial level of 290 DU(5ndash10) assessed bylatitude

Only transgressedover Antarctica inAustral spring(~200 DU)

Oceanacidification(R2009same)

Carbonate ionconcentrationaverage globalsurface oceansaturation state withrespect to aragonite(Warag)

ge80 of the pre-industrialaragonite saturation state ofmean surface ocean includingnatural diel and seasonalvariability (ge80ndash ge70)

~84 of thepre-industrialaragonitesaturation state

Biogeochemicalflows (P andN cycles)(R2009Biogeochemicalflows (interferencewith P and Ncycles))

P Global P flowfrom freshwatersystems into theocean

P Regional P flowfrom fertilizers toerodible soils

N Global Industrialand intentionalbiological fixationof N

11 Tg P yrndash1 (11ndash100 Tg P yrndash1)

62 Tg yrndash1 mined and applied toerodible (agricultural) soils(62-112 Tg yrndash1) Boundary is aglobal average but regionaldistribution is critical forimpacts

62 Tg N yrndash1 (62ndash82 Tg N yrndash1)Boundary acts as a globallsquovalversquo limiting introduction ofnew reactive N to Earth Systembut regional distribution offertilizer N is critical forimpacts

~22 Tg P yrndash1

~14 Tg P yrndash1

~150 Tg N yrndash1

RESEARCH | RESEARCH ARTICLE

events inmany regions of the world is increasing(17) changes in atmospheric circulation patternshave increased drought in some regions of theworld (17) and the rate of combined mass lossfrom the Greenland and Antarctic ice sheets isincreasing (36)

Changes in biosphere integrity

We propose a two-component approach address-ing two key roles of the biosphere in the Earthsystem The first captures the role of geneticallyunique material as the ldquoinformation bankrdquo thatultimately determines the potential for life to

continue to coevolve with the abiotic componentof the Earth system in the most resilient waypossible Genetic diversity provides the long-termcapacity of the biosphere to persist under andadapt to abrupt and gradual abiotic change Thesecond captures the role of the biosphere inEarth-system functioning through the value rangedistribution and relative abundance of the func-tional traits of the organisms present in an eco-system or biota (7)For the first role the concept of phylogenetic

species variability (PSV) (7 33 37) would be anappropriate control variable However because

global data are not yet available for PSV we re-tain the global extinction rate as an interim con-trol variable although it is measured inaccuratelyand with a time lag There may be a considerablerisk in using extinction rate as a control variablebecause phylogenetic (and functional) diversitymay be more sensitive to human pressures thanspecies-level diversity (38) In principle the bound-ary should be set at a rate of loss of PSV no greaterthan the rate of evolution of new PSV during theHolocene Because that is unknown wemust fallback on the (imperfectly) known extinction rateof well-studied organisms over the past several

SCIENCE sciencemagorg 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 1259855-5

Earth-systemprocess

Controlvariable(s)

Planetary boundary(zone of uncertainty)

Current value ofcontrol variable

Land-systemchange(R2009same)

Global Area offorested land as of original forestcover

Biome Area offorested land as of potential forest

Global 75 (75ndash54) Valuesare a weighted average of thethree individual biomeboundaries and their uncertaintyzones

BiomeTropical 85 (85ndash60)Temperate 50 (50ndash30)Boreal 85 (85ndash60)

62

Freshwateruse(R2009Globalfreshwateruse)

Global Maximumamount ofconsumptive bluewater use (km3yrndash1)

Basin Blue waterwithdrawal as ofmean monthly riverflow

Global 4000 km3 yrndash1

(4000ndash6000 km3 yrndash1)

Basin Maximum monthlywithdrawal as a percentageof mean monthly river flowFor low-flow months 25(25ndash55) for intermediate-flow months 30 (30ndash60)for high-flow months 55(55ndash85)

~2600 km3 yrndash1

Atmosphericaerosolloading(R2009same)

Global AerosolOptical Depth(AOD) but muchregional variation

Regional AOD asa seasonal averageover a region SouthAsian Monsoonused as a case study

Regional (South AsianMonsoon as a case study)anthropogenic total (absorbingand scattering) AOD overIndian subcontinent of 025(025ndash050) absorbing(warming) AOD less than 10of total AOD

030 AOD overSouth Asianregion

Introductionof novel entities(R2009 Chemicalpollution)

No control variablecurrently defined

No boundary currentlyidentified but see boundaryfor stratospheric ozone for anexample of a boundaryrelated to a novel entity (CFCs)

RESEARCH | RESEARCH ARTICLE

million yearsmdashabout 1 per million species-years(39)mdashand add a large uncertainty bound raisingthe boundary to 10 permillion species-years Therisk is that although the Earth system can tol-erate a higher-than-background level of extinc-tions for a time we do not knowwhat levels of ortypes of biodiversity lossmay possibly trigger non-linear or irreversible changes to the Earth systemThe second control variable aims to capture the

role of the biosphere in Earth-system functioningand measures loss of biodiversity components atboth global and biomelarge ecosystem levels Al-though several variables have been developed atlocal scales for measuring functional diversity[eg (40)] finding an appropriate control varia-ble at regional or global levels is challenging Forthe present we propose an interim control var-iable the Biodiversity Intactness Index (BII) (41)BII assesses change in population abundance as aresult of human impacts such as land or resourceuse across a wide range of taxa and functionalgroups at a biome or ecosystem level using pre-industrial era abundance as a reference point Theindex typically ranges from 100 (abundancesacross all functional groups at preindustrial levels)to lower values that reflect the extent and degreeof human modification of populations of plantsand animals BII values for particular functionalgroups can go above 100 if humanmodificationsto ecosystems lead to increases in the abundanceof those speciesDue to a lack of evidence on the relationship

between BII and Earth-system responses we pro-

pose a preliminary boundary at 90 of the BIIbut with a very large uncertainty range (90 to30) that reflects the large gaps in our knowl-edge about the BIIndashEarth-system functioningrelationship (42 43) BII has been so far appliedto southern Africarsquos terrestrial biomes only (seefig S3 for an estimation of aggregated humanpressures on the terrestrial biosphere globally)where the index (not yet disaggregated to func-tional groups) was estimated to be 84 BIIranged from 69 to 91 for the seven countrieswhere it has been applied (41) Observations acrossthese countries suggest that decreases in BII ad-equately capture increasing levels of ecosystemdegradation defined as land uses that do not al-ter the land-cover type but lead to a persistentloss in ecosystem productivity (41)In addition to further work on functional mea-

sures such as BII in the longer term the conceptof biome integritymdashthe functioning and persist-ence of biomes at broad scales (7)mdashoffers a prom-ising approach and with further research couldprovide a set of operational control variables (oneper biome) that is appropriate robust and scien-tifically based

Stratospheric ozone depletion

We retain the original control variable [O3 con-centration in DU (Dobson units)] and boundary(275 DU) This boundary is only transgressedover Antarctica in the austral spring when O3

concentration drops to about 200 DU (44) How-ever the minimum O3 concentration has been

steady for about 15 years and is expected to riseover the coming decades as the ozone hole isrepaired after the phasing out of ozone-depletingsubstances This is an example in which after aboundary has been transgressed regionally hu-manity has taken effective action to return theprocess back to within the boundary

Ocean acidification

This boundary is intimately linked with one ofthe control variables CO2 for the climate changePB The concentration of free H+ ions in the sur-face ocean has increased by about 30 over thepast 200 years due to the increase in atmosphericCO2 (45) This in turn influences carbonate chem-istry in surface ocean waters Specifically it lowersthe saturation state of aragonite (Warag) a form ofcalcium carbonate formed by many marine orga-nisms At Warag lt 1 aragonite will dissolve Nonew evidence has emerged to suggest that theoriginally proposed boundary (ge80 of the pre-industrial average annual global Warag) shouldbe adjusted although geographical heterogeneityin Warag is important in monitoring the state ofthe boundary around the worldrsquos oceans (fig S4)Currently Warag is approximately equal to 84 ofthe preindustrial value (46) This boundary wouldnot be transgressed if the climate-change bound-ary of 350 ppm CO2 were to be respected

Biogeochemical flows

The original boundary was formulated for phos-phorus (P) and nitrogen (N) only but we nowpropose a more generic PB to encompass humaninfluence on biogeochemical flows in general Al-though the carbon cycle is covered in the climate-change boundary other elements such as silicon(47 48) are also important for Earth-system func-tioning Furthermore there is increasing evidencethat ratios between elements in the environmentmay have impacts on biodiversity on land and inthe sea (49ndash51) Thus we may ultimately need todevelop PBs for other elements and their ratiosalthough for now we focus on P and N onlyA two-level approach is now proposed for the

P component of the biogeochemical flows bound-ary (see also the supplementary materials) Theoriginal global-level boundary based on the pre-vention of a large-scale ocean anoxic event isretained with the proposed boundary set at asustained flow of 11 Tg P yearndash1 from freshwatersystems into the ocean Based on the analysis ofCarpenter and Bennett (3) we now propose anadditional regional-level P boundary designedto avert widespread eutrophication of freshwatersystems at a flow of 62 Tg P yearndash1 from fer-tilizers (mined P) to erodible soilsGiven that the addition of P to regional

watersheds is almost entirely from fertilizers theregional-level boundary applies primarily to theworldrsquos croplands The current global rate of ap-plication of P in fertilizers to croplands is 142 TgP yearndash1 (52 53) Observations point toward a fewagricultural regions of very high P applicationrates as the main contributors to the transgres-sion of this boundary (Fig 2 and fig S5A) andsuggest that a redistribution of P from areas

1259855-6 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 sciencemagorg SCIENCE

Fig 3The current status of the control variables for seven of the nine planetary boundaries Thegreen zone is the safe operating space (below the boundary) yellow represents the zone of uncertainty(increasing risk) and red is the high-risk zoneThe planetary boundary itself lies at the inner heavy circleThe control variables have been normalized for the zone of uncertainty (between the two heavy circles)the center of the figure therefore does not represent values of 0 for the control variables The controlvariable shown for climate change is atmospheric CO2 concentration Processes for which global-levelboundaries cannot yet be quantified are represented by gray wedges these are atmospheric aerosolloading novel entities and the functional role of biosphere integrity Modified from (1)

RESEARCH | RESEARCH ARTICLE

where it is currently in excess to areas where thesoil is naturally P-poormay simultaneously boostglobal crop production and reduce the transgres-sion of the regional-level P boundary (3 52 54)The N boundary has been taken from the com-

prehensive analysis of de Vries et al (5) whichproposed a PB for eutrophication of aquatic eco-systems of 62 Tg N yearndash1 from industrial andintentional biological N fixation using the moststringent water quality criterion As for the Pboundary a few agricultural regions of very highN application rates are the main contributors tothe transgression of this boundary (Fig 2 andfig S5B) This suggests that a redistribution of Ncould simultaneously boost global crop produc-tion and reduce the transgression of the regional-level boundaryBecause the major anthropogenic perturba-

tion of both the N and P cycles arises from fertil-izer application we can analyze the links betweenthe independently determined N and P bounda-ries in an integrated way based on the NP ratioin the growing plant tissue of agricultural cropsApplying this ratio which is on average 118 (55)to the P boundary (62 Tg P yearndash1) gives an Nboundary of 73 Tg N yearndash1 Conversely applyingthe ratio to theN boundary (62 TgN yearndash1) givesa P boundary of 53 Tg P yearndash1 The small dif-ferences between the boundaries derived usingthe NP ratio and those calculated independent-ly which are likely nonsignificant differencesgiven the precision of the data available for thecalculations show the internal consistency inour approach to the biogeochemical boundariesMore detail on the development of the P andN

boundaries is given in (33) where we also em-phasize that the proposed P and N boundariesmay be larger for an optimal allocation of N (andP) over the globe

Land-system change

The updated biosphere integrity boundary pro-vides a considerable constraint on the amountand pattern of land-system change in all ter-restrial biomes forests woodlands savannasgrasslands shrublands tundra and so on Theland-system change boundary is now focusedmore tightly on a specific constraint the biogeo-physical processes in land systems that directlyregulate climatemdashexchange of energy water andmomentum between the land surface and theatmosphere The control variable has been changedfrom the amount of cropland to the amount offorest cover remaining as the three major forestbiomesmdashtropical temperate and borealmdashplay astronger role in land surfacendashclimate couplingthan other biomes (56 57) In particular we fo-cus on those land-system changes that can in-fluence the climate in regions beyond the regionwhere the land-system change occurredOf the forest biomes tropical forests have sub-

stantial feedbacks to climate through changes inevapotranspiration when they are converted tononforested systems and changes in the distribu-tion of boreal forests affect the albedo of the landsurface and hence regional energy exchange Bothhave strong regional and global teleconnections

The biome-level boundary for these two types offorest have been set at 85 (Table 1 and thesupplementary materials) and the boundary fortemperate forests has been proposed at 50 ofpotential forest cover because changes to tem-perate forests are estimated to have weaker in-fluences on the climate system at the global levelthan changes to the other two major forestbiomes (56) These boundaries would almostsurely be met if the proposed biosphere integ-rity boundary of 90 BII were respectedEstimates of the current status of the land-

system change boundary are given in Figs 2 and3 and fig S6 and in (58)

Freshwater use

The revised freshwater use boundary has retainedconsumptive use of blue water [from rivers lakesreservoirs and renewable groundwater stores(59)] as the global-level control variable and4000 km3year as the value of the boundaryThis PB may be somewhat higher or lower de-pending on riversrsquo ecological flow requirements(6) Therefore we report here a new assessmentto complement the PB with a basin-scale bound-ary for the maximum rate of blue water with-drawal along rivers based on the amount of waterrequired in the river system to avoid regime shiftsin the functioning of flow-dependent ecosystemsWe base our control variable on the concept ofenvironmental water flows (EWF) which definesthe level of river flows for different hydrologicalcharacteristics of river basins adequate to main-tain a fair-to-good ecosystem state (60ndash62)The variable monthly flow (VMF) method

(33 63) was used to calculate the basin-scaleboundary for water This method takes accountof intra-annual variability by classifying flow re-gimes into high- intermediate- and low-flowmonths and allocating EWF as a percentage ofthe mean monthly flow (MMF) Based on thisanalysis the zones of uncertainty for the river-basin scale water boundary were set at 25 to 55of MMF for the low-flow regime 40 to 70 forthe intermediate-flow regime and 55 to 85 forthe high-flow regime (table S2) The boundarieswere set at the lower end of the uncertaintyranges that encompass average monthly EWFOur new estimates of the current status of thewater use boundarymdashcomputed based on gridcellndashspecific estimates of agricultural industrialand domestic water withdrawalsmdashare shown inFigs 2 and 3 with details in figs S7 and S8

Atmospheric aerosol loading

Aerosols have well-known serious human healtheffects leading to about 72 million deaths peryear (64) They also affect the functioning of theEarth system in many ways (65) (fig S9) Herewe focus on the effect of aerosols on regionalocean-atmosphere circulation as the rationalefor a separate aerosols boundary We adopt aero-sol optical depth (AOD) (33) as the control var-iable and use the south Asian monsoon as a casestudy based on the potential of widespread aero-sol loading over the Indian subcontinent to switchthe monsoon system to a drier state

The background AOD over south Asia is ~015and can be as high as 04 during volcanic events(66) Emissions of black carbon and organic car-bon from cooking and heating with biofuels andfrom diesel transportation and emission of sul-fates and nitrates from fossil fuel combustioncan increase seasonal mean AODs to as high as04 (larger during volcanic periods) leading todecreases of 10 to 15 of incident solar radiationat the surface (fig S9) A substantial decrease inmonsoon activity is likely around an AOD of 050an increase of 035 above the background (67)Taking a precautionary approach toward uncer-tainties surrounding the position of the tippingpoint we propose a boundary at an AOD of 025(an increase due to human activities of 01) witha zone of uncertainty of 025 to 050 The annualmean AOD is currently about 03 (66) within thezone of uncertainty

Introduction of novel entities

We define novel entities as new substances newforms of existing substances and modified lifeforms that have the potential for unwanted geo-physical andor biological effects Anthropogenicintroduction of novel entities to the environmentis of concern at the global level when these en-tities exhibit (i) persistence (ii) mobility acrossscales with consequent widespread distributionsand (iii) potential impacts on vital Earth-systemprocesses or subsystems These potentially in-clude chemicals and other new types of engi-neered materials or organisms [eg (68ndash71)] notpreviously known to the Earth system as well asnaturally occurring elements (for example heavymetals) mobilized by anthropogenic activitiesThe risks associated with the introduction ofnovel entities into the Earth system are exempli-fied by the release of CFCs (chlorofluorocarbons)which are very useful synthetic chemicals thatwere thought to be harmless but had unexpecteddramatic impacts on the stratospheric ozone layerIn effect humanity is repeatedly running suchglobal-scale experiments but not yet applying theinsights from previous experience to new appli-cations (72 73)Today there aremore than 100000 substances

in global commerce (74) If nanomaterials andplastic polymers that degrade to microplasticsare included the list is even longer There is alsoa ldquochemical intensificationrdquo due to the rapidlyincreasing global production of chemicals theexpanding worldwide distribution as chemicalproducts or in consumer goods and the exten-sive global trade in chemical wastes (75)In recent years there has been a growing de-

bate about the global-scale effects of chemicalpollution leading to calls for the definition ofcriteria to identify the kinds of chemical sub-stances that are likely to be globally problematic(76 77) Persson et al (73) proposed that there arethree conditions that need to be fulfilled for achemical to pose a threat to the Earth system (i)the chemical has an unknown disruptive effecton a vital Earth-systemprocess (ii) the disruptiveeffect is not discovered until it is a problem at theglobal scale and (iii) the effect is not readily

SCIENCE sciencemagorg 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 1259855-7

RESEARCH | RESEARCH ARTICLE

reversible The challenge to the research commu-nity is to develop the knowledge base that allowsthe screening of chemicals before they are re-leased into the environment for properties thatmay predispose them toward becoming globalproblemsAs a first step toward meeting this challenge

the three conditions outlined above have beenused as the basis for identifying scenarios ofchemical pollution that fulfill the conditions andas a next step for pinpointing chemical profilesthat fit the scenarios (28) This proposal consti-tutes a first attempt at adding the Earth-systemperspective when assessing hazard and risk ofchemicals and offers a vision for a systematic ap-proach to a complex management situation withmany unknownsDespite this progress in developing an Earth-

systemndashoriented approach there is not yet anaggregate global-level analysis of chemical pol-lution on which to base a control variable or aboundary value It may also serve little purposeto define boundary values and control varia-bles for a planetary boundary of this complexityNevertheless there is a potential threat fromnovel entities to disrupt the functioning of theEarth-system and society needs to learn how tomitigate these unknown risks and manage chem-icals under uncertainty (28 73)Some precautionary and preventive actions

can be considered These may include a strongerfocus on green chemistry (78) finding synergieswith risk-reducing interventions in other fieldssuch as occupational health (79) paying moreattention to learning from earlier mistakes (8081) and investing in science to better under-stand and monitor vital Earth-system processesin order to be able to detect disruptive effectsfrom novel entities as early as possible

Hierarchy of boundaries

An analysis of the many interactions among theboundaries (table S3 and fig S10) suggests thattwo of themmdashclimate change and biosphereintegritymdashare highly integrated emergent system-level phenomena that are connected to all of theother PBs They operate at the level of the wholeEarth system (7) and have coevolved for nearly4 billion years (82) They are regulated by theother boundaries and on the other hand pro-vide the planetary-level overarching systems with-in which the other boundary processes operateFurthermore large changes in the climate or inbiosphere integrity would likely on their ownpush the Earth system out of the Holocene stateIn fact transitions between time periods in Earthhistory have often been delineated by substantialshifts in climate the biosphere or both (82 83)These observations suggest a two-level hierar-

chy of boundaries in which climate change andbiosphere integrity should be recognized as coreplanetary boundaries through which the otherboundaries operate The crossing of one or moreof the other boundaries may seriously affect hu-man well-being and may predispose the trans-gression of a core boundary(ies) but does not byitself lead to a new state of the Earth system This

hierarchical approach to classifying the bounda-ries becomes clearer by examining inmore detailthe roles of climate and biosphere integrity in thefunctioning of the Earth systemThe climate system is a manifestation of the

amount distribution and net balance of energyat Earthrsquos surface The total amount of energysets the overall conditions for life In Earthrsquos cur-rent climate a range of global surface temper-atures and atmospheric pressures allows the threephases of water to be present simultaneouslywith ice and water vapor playing critical roles inthe physical feedbacks of the climate system Thedistribution of energy by latitude over the landand sea surfaces and within the ocean plays amajor role in the circulation of the two greatfluids the ocean and the atmosphere These sys-temic physical characteristics are key spatial de-terminants of the distribution of the biota andthe structure and functioning of ecosystems andare controllers of biogeochemical flowsBiosphere integrity is also crucial to Earth-

system functioning where the biosphere is de-fined as the totality of all ecosystems (terrestrialfreshwater andmarine) on Earth and their biota(32) These ecosystems and biota play a criticalrole in determining the state of the Earth systemregulating its material and energy flows and itsresponses to abrupt and gradual change (7) Di-versity in the biosphere provides resilience toterrestrial and marine ecosystems (83 84) Thebiosphere not only interacts with the other plan-etary boundaries but also increases the capacityof theEarth system topersist in a given state underchanges in these other boundaries The ultimatebasis for the many roles that the biosphere playsin Earth-system dynamics is the genetic code ofthe biota the basic information bank that de-fines the biospherersquos functional role and its ca-pacity to innovate and persist into the future

Planetary boundaries in asocietal context

A proposed approach for sustainable develop-ment goals (SDGs) (85) argues that the stablefunctioning of the Earth system is a prereq-uisite for thriving societies around the world Thisapproach implies that the PB framework orsomething like it will need to be implementedalongside the achievement of targets aimed atmore immediate human needs such as provi-sion of clean affordable and accessible energyand the adequate supply of food World devel-opment within the biophysical limits of a stableEarth system has always been a necessity [eg(86 87)] However only recently for a numberof reasons has it become possible to identifyevaluate and quantify risks of abrupt planetary-and biome-level shifts due to overshoot of keyEarth-system parameters (i) the emergence ofglobal-change thinking and Earth-system think-ing (88) (ii) the rise of ldquothe Planetaryrdquo as a rel-evant level of complex system understanding(89ndash92) and (iii) observable effects of the rapidincrease in human pressures on the planet (16)The PB approach is embedded in this emerg-

ing social context but it does not suggest how to

maneuver within the safe operating space in thequest for global sustainability For example thePB framework does not as yet account for the re-gional distribution of the impact or its histor-ical patterns Nor does the PB framework takeinto account the deeper issues of equity and cau-sation The current levels of the boundary pro-cesses and the transgressions of boundaries thathave already occurred are unevenly caused bydifferent human societies and different socialgroups The wealth benefits that these trans-gressions have brought are also unevenly distrib-uted socially and geographically It is easy toforesee that uneven distribution of causation andbenefits will continue and these differentialsmust surely be addressed for a Holocene-likeEarth-system state to be successfully legitimatedand maintained However the PB framework ascurrently construed provides no guidance as tohow this may be achieved [although some po-tential synergies have been noted (54)] and itcannot readily be used tomake choices betweenpathways for piecemeal maneuvering withinthe safe operating space ormore radical shifts ofglobal governance (93)The nature of the PB framework implies that

two important cautions should be observedwhenapplication of the framework to policy or man-agement is proposed boundary interactions andscale

Boundary interactions

The planetary boundaries framework arises fromthe scientific evidence that Earth is a singlecomplex integrated systemmdashthat is the bound-aries operate as an interdependent set [eg(94)] (table S1 and fig S10) Although a system-atic quantitative analysis of interactions amongall of the processes for which boundaries areproposed remains beyond the scope of currentmodeling and observational capacity the Earthsystem clearly operates in well-defined states inwhich these processes and their interactionscan create stabilizing or destabilizing feedbacks(16 90 95) This has profound implications forglobal sustainability because it emphasizes theneed to address multiple interacting environ-mental processes simultaneously (eg stabilizingthe climate system requires sustainable forestmanagement and stable ocean ecosystems)

Scale

The PB framework is not designed to be ldquodown-scaledrdquo or ldquodisaggregatedrdquo to smaller levels suchas nations or local communities That said thePB framework recognizes the importance ofchanges at the level of subsystems in the Earthsystem (eg biomes or large river basins) on thefunctioning of the Earth system as a whole Alsothere are strong arguments for an integrated ap-proach coupling boundary definitions at region-al and global levels with development goals toenable the application of ldquoPB thinkingrdquo at lev-els (nations basins and regions) where policyaction most commonly occurs [eg (85 96)]This update of the PB framework is one step on

a longer-term evolution of scientific knowledge to

1259855-8 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 sciencemagorg SCIENCE

RESEARCH | RESEARCH ARTICLE

inform and support global sustainability goalsand pathways This evolution is needed morethan ever before there are severe implementa-tion gaps inmany global environmental policiesrelating to the PB issues where problematictrends are not being halted or reversed despiteinternational consensus about the urgency of theproblems The prospect of tighter resource con-straints and rising environmental hazards is alsounavoidably turning the focus onto global socialequity and the planetary stewardship of Earthrsquoslife-support system There is a need for a trulyglobal evidence base with much greater integra-tion among issues in order to respond to theseglobal challenges New research initiatives [egFuture Earth (wwwfutureearthorg)] provide evi-dence that science can respond to this need byapplying Earth-system research to advance a newgeneration of integrated global analyses and toexplore options for transformations toward sus-tainability This is a clear sign that as the risksof the Anthropocene to human well-being be-come clearer research is maturing to a pointwhere a systemic step-change is possiblemdashandnecessarymdashin exploring and defining a safe andjust planetary operating space for the furtherdevelopment of human societies

Methods summary

Our approach to building the planetary bound-aries framework is described above We haveimplemented the framework through an ex-pert assessment and synthesis of the scientificknowledge of intrinsic biophysical processes thatregulate the stability of the Earth system Ourprecautionary approach is based on the main-tenance of a Holocene-like state of the Earthsystem and on an assessment of the level ofhuman-driven change that would risk destabi-lizing this state For the climate change PB thereis already much literature on which to basesuch an assessment For others such as strato-spheric ozone ocean acidification extinctionrates and P andN cycles we have used estimatesof preindustrial values of the control variableas a Holocene baseline Where large undesira-ble thresholds exist and have been studied (egpolar ice sheets Amazon rainforest aragonitedissolution atmospheric aerosols and the southAsian monsoon) quantitative boundaries can bereadily proposed For others where the focus ison erosion of Earth-system resilience the bound-aries are more difficult (but not impossible) toquantify as reflected in larger uncertainty zonesWe used large-scale assessments of the impacts

of human activities on Earth-system functioning[eg Intergovernmental Panel on Climate Change(17 18) the International Geosphere-BiosphereProgramme synthesis (16) and chemicals (75 80)]as sources of community-level understandingon which to propose PBs Our update has alsorelied on post-2009 assessments of individualboundaries by the relevant expert research com-munities examples include phosphorus (3) ni-trogen (5) biosphere integrity (7) freshwater use(5 63) and novel entities [with a focus on chem-icals (28 73)] Finally some new analyses have

been undertaken specifically for this paper (i) afreshwater-use PB based on the EWF approach(33 63) (ii) the linkage of the phosphorus andnitrogen boundaries via the NP ratio in grow-ing crop tissue (33) and (iii) the use of majorforest biomes as the basis for the land-systemchange PB (33)

REFERENCES AND NOTES

1 J Rockstroumlm et al Planetary boundaries Exploring the safeoperating space for humanity Ecol Soc 14 32 (2009)httpwwwecologyandsocietyorgvol14iss2art32

2 J Rockstroumlm et al A safe operating space for humanityNature 461 472ndash475 (2009) doi 101038461472apmid 19779433

3 S R Carpenter E M Bennett Reconsideration of theplanetary boundary for phosphorus Environ Res Lett 6014009 (2011) doi 1010881748-932661014009

4 S W Running Ecology A measurable planetary boundaryfor the biosphere Science 337 1458ndash1459 (2012)doi 101126science1227620 pmid 22997311

5 W de Vries J Kros C Kroeze S P Seitzinger Assessingplanetary and regional nitrogen boundaries related to foodsecurity and adverse environmental impacts Curr OpinionEnviron Sust 5 392ndash402 (2013) doi 101016jcosust201307004

6 D Gerten et al Towards a revised planetary boundary forconsumptive freshwater use Role of environmental flowrequirements Curr Opinion Environ Sust 5 551ndash558 (2013)doi 101016jcosust201311001

7 G M Mace et al Approaches to defining a planetary boundaryfor biodiversity Glob Environ Change 28 289ndash297 (2014)doi 101016jgloenvcha201407009

8 V Galaz Global Environmental Governance Technology andPolitics The Anthropocene Gap (Edward Elgar CheltenhamUK 2014)

9 UN GSP (UN High-Level Panel on Global Sustainability)Resilient People Resilient Planet A Future Worth Choosing(Report for the 2012 Rio+20 Earth Summit United NationsNew York 2012)

10 WBCSD (World Business Council on Sustainable Development)Action 2020 Overview (WBCSD Geneva Switzerlandhttpaction2020org accessed 18 June 2014)

11 R Costanza L Graumlich W Steffen Eds Integrated Historyand Future of People on Earth (MIT Press CambridgeMA USA 2006)

12 S Soumlrlin P Warde in Naturersquos End History and theEnvironment S Soumlrlin P Warde Eds (Palgrave MacMillanLondon 2009) pp 1ndash19

13 R C Bishop Endangered species and uncertainty Theeconomics of a safe minimum standard Am J Agric Econ 6110ndash18 (1978) doi 1023071240156

14 T M Crowards Safe minimum standards Costs andopportunities Ecol Econ 25 303ndash314 (1998) doi 101016S0921-8009(97)00041-4

15 W Steffen J Crutzen J R McNeill The Anthropocene Arehumans now overwhelming the great forces of NatureAmbio 36 614ndash621 (2007) doi 1015790044-7447(2007)36[614TAAHNO]20CO2 pmid 18240674

16 W Steffen et al Global Change and the Earth System A PlanetUnder Pressure (The IGBP Book Series Springer-VerlagBerlin Heidelberg New York 2004)

17 IPCC (Intergovernmental Panel on Climate Change) Managingthe risks of extreme events and disasters to advanceclimate change adaptation A special report of Working GroupsI and II of the IPCC CB Field et al Eds (CambridgeUniversity Press Cambridge UK (2012) doi 101017CBO9781139177245

18 IPCC (Intergovernmental Panel on Climate Change) ClimateChange 2013 The Physical Science Basis Summary forPolicymakers L Alexander et al Eds (IPCC SecretariatGeneva Switzerland 2013) doi 101017CBO9781107415324

19 P J Crutzen Geology of mankind Nature 415 23 (2002)doi 101038415023a pmid 11780095

20 K Richardson W Steffen D Liverman Climate Change GlobalRisks Challenges and Decisions (Cambridge Univ PressCambridge UK 2011)

21 T M Lenton et al Tipping elements in the Earthrsquos climatesystem Proc Natl Acad Sci USA 105 1786ndash1793 (2008)doi 101073pnas0705414105 pmid 18258748

22 M Scheffer et al Early-warning signals for criticaltransitions Nature 461 53ndash59 (2009) doi 101038nature08227 pmid 19727193

23 S R Carpenter W A Brock Rising variance A leadingindicator of ecological transition Ecol Lett 9 311ndash318 (2006)doi 101111j1461-0248200500877x pmid 16958897

24 J Bakke et al Rapid oceanic and atmospheric changes duringthe Younger Dryas cold period Nat Geosci 2 202ndash205(2009) doi 101038ngeo439

25 M Scheffer et al Anticipating critical transitions Science338 344ndash348 (2012) doi 101126science1225244pmid 23087241

26 R Wang et al Flickering gives early warning signals of acritical transition to a eutrophic lake state Nature 492419ndash422 (2012) doi 101038nature11655 pmid 23160492

27 R Biggs S R Carpenter W A Brock Turning back fromthe brink Detecting an impending regime shift in time to avertit Proc Natl Acad Sci USA 106 826ndash831 (2009)doi 101073pnas0811729106 pmid 19124774

28 M MacLeod et al Identifying chemicals that are planetaryboundary threats Environ Sci Technol 48 11057ndash11063(2014) doi 101021es501893m pmid 25181298

29 C S Holling Resilience and stability of ecological systemsAnnu Rev Ecol Syst 4 1ndash23 (1973) doi 101146annureves04110173000245

30 C Folke et al Resilience thinking Integrating resilienceadaptability and transformability Ecol Soc 15 20 (2010)wwwecologyandsocietyorgvol15iss4art20

31 T P Hughes S Carpenter J Rockstroumlm M SchefferB Walker Multiscale regime shifts and planetary boundariesTrends Ecol Evol 28 389ndash395 (2013) doi 101016jtree201305019 pmid 23769417

32 T M Lenton H T P Williams On the origin of planetary-scaletipping points Trends Ecol Evol 28 380ndash382 (2013)doi 101016jtree201306001 pmid 23777818

33 Supplementary text figures and tables are available onScience Online

34 NOAA (National Oceanic and Atmospheric Administration)NOAA-ESRL Annual CO2 Data accessed at httpco2noworgCurrent-CO2CO2-Nowannual-co2html (2014)

35 S E Perkins L V Alexander J Nairn Increasing frequencyintensity and duration of observed global heat waves and warmspells Geophys Res Lett 39 L20714 (2012) doi 1010292012GL053361

36 A Shepherd et al A reconciled estimate of ice-sheet massbalance Science 338 1183ndash1189 (2012) doi 101126science1228102 pmid 23197528

37 M R Helmus T J Bland C K Williams A R IvesPhylogenetic measures of biodiversity Am Nat 169 E68ndashE83(2007) doi 101086511334 pmid 17230400

38 S Drsquoagata et al Human-mediated loss of phylogeneticand functional diversity in coral reef fishes Curr Biol24 555ndash560 (2014) doi 101016jcub201401049pmid 24560574

39 A D Barnosky et al Has the Earthrsquos sixth mass extinctionalready arrived Nature 471 51ndash57 (2011) doi 101038nature09678 pmid 21368823

40 N W Mason F de Bello D Mouillot S Pavoine S Dray Aguide for using functional diversity indices to reveal changesin assembly processes along ecological gradients J VegSci 24 794ndash806 (2013) doi 101111jvs12013

41 R J Scholes R Biggs A biodiversity intactness index Nature434 45ndash49 (2005) doi 101038nature03289pmid 15744293

42 B Cardinale Ecology Impacts of biodiversity loss Science336 552ndash553 (2012) doi 101126science1222102pmid 22556243

43 D U Hooper et al A global synthesis reveals biodiversityloss as a major driver of ecosystem change Nature 486105ndash108 (2012) doi 101038nature11118pmid 22678289

44 BAS (British Antarctic Survey) ldquoAntarctic ozonerdquo wwwantarcticaacukmetjdsozoneindexhtmldata J ShanklinBritish Antarctic Survey (2013)

45 Royal Society Ocean Acidification Due to IncreasingAtmospheric Carbon Dioxide Policy Document 1205 (TheRoyal Society London 2005)

46 J M Guinotte V J Fabry Ocean acidification and its potentialeffects on marine ecosystems Ann N Y Acad Sci 1134320ndash342 (2008) doi 101196annals1439013pmid 18566099

47 D J Conley Terrestrial ecosystems and the globalbiogeochemical silica cycle Global Biogeochem Cycles 16681ndash688 (2002) doi 1010292002GB001894

SCIENCE sciencemagorg 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 1259855-9

RESEARCH | RESEARCH ARTICLE

48 F Vandevenne E Struyf W Clymans P Meire Agriculturalsilica harvest Have humans created a new loop in the globalsilica cycle Front Ecol Environ 10 243ndash248 (2012)doi 101890110046

49 S E Gress T D Nichols C C Northcraft W T PeterjohnNutrient limitation in soils exhibiting differing nitrogenavailabilities What lies beyond nitrogen saturation Ecol 88119ndash130 (2007) doi 1018900012-9658(2007)88[119NLISED]20CO2 pmid 17489460

50 H Hillebrand V Lehmpfuhl Resource stoichiometry andconsumers control the biodiversity-productivity relationship inpelagic metacommunities Am Nat 178 171ndash181 (2011)doi 101086660831 pmid 21750381

51 C M Moore et al Processes and patterns of oceanic nutrientlimitation Nat Geosci 6 701ndash710 (2013) doi 101038ngeo1765

52 G K MacDonald E M Bennett P A Potter N RamankuttyAgronomic phosphorus imbalances across the worldrsquoscroplands Proc Natl Acad Sci USA 108 3086ndash3091 (2011)doi 101073pnas1010808108 pmid 21282605

53 L Bouwman et al Exploring global changes in nitrogen andphosphorus cycles in agriculture induced by livestockproduction over the 1900-2050 period Proc Natl AcadSci USA 110 20882ndash20887 (2013) doi 101073pnas1012878108 pmid 21576477

54 W Steffen M Stafford Smith Planetary boundaries equityand global sustainability Why wealthy countries could benefitfrom more equity Curr Opinion Environ Sust 5 403ndash408(2013) doi 101016jcosust201304007

55 D J Greenwood et al A unifying concept for the dependenceof whole-crop N P ratio on biomass theory and experimentAnn Bot (Lond) 102 967ndash977 (2008) doi 101093aobmcn188 pmid 18840873

56 P K Snyder C Delire J A Foley Evaluating the influence ofdifferent vegetation biomes on the global climate Clim Dyn23 279ndash302 (2004) doi 101007s00382-004-0430-0

57 P C West G T Narisma C C Barford C J KucharikJ A Foley An alternative approach for quantifying climateregulation by ecosystems Front Ecol Environ 9 126ndash133(2010) doi 101890090015

58 EPI (Earth Policy Institute) ldquoForest coverrdquo wwwearthpolicyorgindicatorsC56forests_2012_ (2014)

59 M Falkenmark Meeting water requirements of an expandingworld population Philos Trans R Soc Lond B Biol Sci 352929ndash936 (1997) doi 101098rstb19970072

60 J S Wallace M C Acreman C A Sullivan The sharing ofwater between society and ecosystems From conflict tocatchment-based co-management Philos Trans R Soc LondB Biol Sci 358 2011ndash2026 (2003) doi 101098rstb20031383 pmid 14728795

61 N L Poff et al The natural flow regime A paradigm for riverconservation and restoration BioSci 47 769ndash784 (1997)doi 1023071313099

62 N L Poff J K H Zimmerman Ecological responses to alteredflow regimes A literature review to inform the science andmanagement of environmental flows Biol 55 194ndash205 (2010)doi 101111j1365-2427200902272x

63 A V Pastor F Ludwig H Biemans H Hoff P KabatAccounting for environmental flow requirements in globalwater assessments Hydrol Earth Syst Sci 18 5041ndash5059(2014) doi 105194hess-18-5041-2014

64 WHO (World Health Organization) Burden of Disease from theJoint Effects of Household and Ambient Air Pollution for 2012(wwwwhointphehealth_topicsoutdoorairdatabasesFINAL_HAP_AAP_BoD24March2014pdf accessed 23 June 2014httpwwwwhointphehealth_topicsoutdoorairdatabasesen)

65 O Boucher et al in Climate Change 2013 The Physical ScienceBasis IPCC AR5 WGI report T Stocker et al Eds (CambridgeUniv Press Cambridge UK 2013) chap 7 pp 571ndash657

66 M Chin et al Multi-decadal aerosol variations from 1980 to2009 A perspective from observations and a global modelAtmos Chem Phys 14 3657ndash3690 (2014) doi 105194acp-14-3657-2014

67 V Ramanathan et al Atmospheric brown clouds Impacts onSouth Asian climate and hydrological cycle Proc Natl AcadSci USA 102 5326ndash5333 (2005) doi 101073pnas0500656102 pmid 15749818

68 M Cole P Lindeque C Halsband T S Galloway Microplasticsas contaminants in the marine environment A review MarPollut Bull 62 2588ndash2597 (2011) doi 101016jmarpolbul201109025 pmid 22001295

69 EEA (European Environment Agency) Genetically ModifiedOrganisms (GMOs) The Significance of Gene Flow ThroughPollen Transfer (Environmental Issue Report 28 EuropeanEnvironment Agency Copenhagen Denmark 2002)

70 J A Ivar do Sul M F Costa The present and future ofmicroplastic pollution in the marine environment Environ Pollut185 352ndash364 (2014) doi 101016jenvpol201310036pmid 24275078

71 R Kessler Engineered nanoparticles in consumer productsUnderstanding a new ingredient Environ Health Perspect 119a120ndasha125 (2011) doi 101289ehp119-a120 pmid 21356630

72 M Rees Our Final Century Will Civilisation Survive theTwenty-first Century (Arrow Books London 2003)

73 L M Persson et al Confronting unknown planetary boundarythreats from chemical pollution Environ Sci Technol 4712619ndash12622 (2013) doi 101021es402501c pmid 23980998

74 P P Egeghy et al The exposure data landscape formanufactured chemicals Sci Total Environ 414 159ndash166(2012) doi 101016jscitotenv201110046 pmid 22104386

75 UNEP (United Nations Environment Programme) GCOGlobal Chemicals Outlook Towards Sound Management ofChemicals (United Nations Environment ProgrammeNairobi Kenya 2013)

76 S Strempel M Scheringer C A Ng K HungerbuumlhlerScreening for PBT chemicals among the ldquoexistingrdquo andldquonewrdquo chemicals of the EU Environ Sci Technol 465680ndash5687 (2012) doi 101021es3002713pmid 22494215

77 M Scheringer et al How many persistent organic pollutantsshould we expect Atmos Poll Res 3 383ndash391 (2012)doi 105094APR2012044

78 K Sanderson Chemistry Itrsquos not easy being green Nature469 18ndash20 (2011) doi 101038469018a pmid 21209638

79 P A Schulte et al Occupational safety and health greenchemistry and sustainability A review of areas ofconvergence Environ Health 12 31 (2013) doi 1011861476-069X-12-31 pmid 23587312

80 EEA (European Environment Agency) Late Lessons from EarlyWarnings The Precautionary Principle 1896-2000 (EnvironmentalIssue Report 222001 Copenhagen Denmark 2001)

81 D Gee Late lessons from early warnings Toward realism andprecaution with endocrine-disrupting substances EnvironHealth Perspect 114 (suppl 1) 152ndash160 (2006) doi 101289ehp8134 pmid 16818262

82 T Lenton A Watson A Revolutions That Made the Earth(Oxford Univ Press Oxford UK 2011)

83 R Biggs et al Toward principles for enhancing the resilienceof ecosystem services Annu Rev Environ Resour 37421ndash448 (2012) doi 101146annurev-environ-051211-123836

84 G S Cumming P Olsson F S Chapin III C S HollingResilience experimentation and scale mismatches in social-ecological systems Landscape Ecol 28 1139ndash1150 (2013)doi 101007s10980-012-9725-4

85 D Griggs et al Policy Sustainable development goals forpeople and planet Nature 495 305ndash307 (2013) doi 101038495305a pmid 23518546

86 R Costanza Ed Ecological Economics The Science andManagement of Sustainability (Columbia Univ PressNew York 1991)

87 C Folke in Linking the Natural Environment and the EconomyEssays from the Eco-Eco Group C Folke T Karingberger Eds(Kluwer Academic Publishers Dordrecht Netherlands 1991)pp 77ndash94

88 L Robin S Soumlrlin P Warde Eds The Future of NatureDocuments of Global Change (Yale Univ Press New Haven CT2013)

89 U Heise Sense of Place and Sense of Planet TheEnvironmental Imagination of the Global (Oxford Univ PressOxford 2008)

90 M Scheffer Critical Transitions in Nature and Society(Princeton Univ Press Princeton NJ 2009)

91 J Masco Bad weather On planetary crisis Soc Stud Sci 407ndash40 (2010) doi 1011770306312709341598

92 G Paacutelsson et al Reconceptualizing the lsquoAnthroposrsquo in theAnthropocene Integrating the social sciences and humanitiesin global environmental change research Environ Sci Policy28 4 (2013) doi 101016jenvsci201211004

93 N Castree et al Changing the intellectual climate NatureClim Change 4 763ndash768 (2014) doi 101038nclimate2339

94 J M Anderies S R Carpenter W Steffen J Rockstroumlm Thetopology of non-linear global carbon dynamics From tippingpoints to planetary boundaries Environ Res Lett 8 044048(2013) doi 1010881748-932684044048

95 S E Cornell I C Prentice J I House C J DownyUnderstanding the Earth System Global Change Science forApplication (Cambridge Univ Press Cambridge 2012)

96 J A Dearing et al Safe and just operating spaces for regionalsocial-ecological systems Glob Environ Change 28 227ndash238(2014) doi 101016jgloenvcha201406012

ACKNOWLEDGMENTS

We thank J Foley and N Ramunkutty for contributions to theland-system change boundary A Pastor for analytical work on thePB for freshwater B Armstrong C Butler T McMichael andA Woodward for contributions to the novel entities boundary andB Scholes for comments on an earlier version of the manuscriptData associated with the paper are located at the StockholmResilience Centre Sweden (httpwwwstockholmresilienceorg21researchresearch-programmesplanetary-boundarieshtml)The planetary boundaries research at the Stockholm ResilienceCentre is made possible through a core grant from MISTRA(Swedish Foundation for Strategic Environmental Research) SECis supported by the Swedish Research Council EMB is supportedby the Natural Sciences and Engineering Research Council ofCanada and by the Trottier Institute for Science and Public PolicyRB is supported by a Branco Weiss Fellowship CF is supportedby the Family Erling Persson Academy Programme on GlobalEconomic Dynamics and the Biosphere IF is supported by theStordalen Foundation (Norway) SS is supported by theRiksbanken Jubileumsfond and the Institute for Advanced StudyPrinceton NJ and SRC and VR are supported bythe US National Science Foundation

SUPPLEMENTARY MATERIALS

wwwsciencemagorgcontent34762231259855supplDC1MethodsFigs S1 to S10Tables S1 to S3References (97ndash158)

11 August 2014 accepted 8 January 2015Published online 15 January 2015101126science1259855

1259855-10 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 sciencemagorg SCIENCE

RESEARCH | RESEARCH ARTICLE

DOI 101126science1259855 (2015)347 Science

et alWill SteffenplanetPlanetary boundaries Guiding human development on a changing

This copy is for your personal non-commercial use only

clicking herecolleagues clients or customers by you can order high-quality copies for yourIf you wish to distribute this article to others

herefollowing the guidelines

can be obtained byPermission to republish or repurpose articles or portions of articles

) February 12 2015 wwwsciencemagorg (this information is current as of

The following resources related to this article are available online at

httpwwwsciencemagorgcontent34762231259855fullhtmlversion of this article at

including high-resolution figures can be found in the onlineUpdated information and services

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can berelated to this article A list of selected additional articles on the Science Web sites

httpwwwsciencemagorgcontent34762231259855fullhtmlref-list-1 27 of which can be accessed freecites 120 articlesThis article

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subject collectionsThis article appears in the following

registered trademark of AAAS is aScience2015 by the American Association for the Advancement of Science all rights reserved The title

CopyrightAmerican Association for the Advancement of Science 1200 New York Avenue NW Washington DC 20005 (print ISSN 0036-8075 online ISSN 1095-9203) is published weekly except the last week in December by theScience

on

Feb

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201

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of the Earth system To do this we propose thedevelopment of a two-level set of control var-iables and boundaries The subglobal-level unitsof analysis for these six boundaries are notidentical they vary according to the role that theprocesses play in the Earth system (i) changesin biosphere integrity occur at the level of land-based biomes large freshwater ecosystems ormajor marine ecosystems as the largest sub-global unit (ii) the role of direct human-drivenland-system change in biophysical climate regu-lation is primarily related to changes in forestbiomes (iii) freshwater flows and use occur atthe largest subglobal level in the major riverbasins around the world and (iv) changes inbiogeochemical flows exemplified by phospho-rus and nitrogen cycling aggregate from rela-tively localized but very severe perturbationsin intensive agricultural zones to affect globalflows of nutrients We recognize these as crit-ical regions for Earth-system functioningWhereappropriate the updates of the individual bound-aries (see below) (33) now contain both the glob-ally aggregated boundary value of the controlvariable and its regional distribution functionFigure 2 shows the distributions and currentstatus of the control variables for three of theboundaries where subglobal dynamics are crit-

ical biogeochemical cycles land-system changeand freshwater useWe emphasize that our subglobal-level focus is

based on the necessity to consider this level tounderstand the functioning of the Earth systemas awhole The PB framework is thereforemeantto complement not replace or supersede effortsto address local and regional environmental issues

Updates of the individual boundaries

Brief updates of all nine of the PBs are given inthis section and more detailed descriptions ofthe updates for three of the PBs that have under-gone more extensive revision can be found in (33)The geographical distribution issues discussedabove are particularly important for five of thePBs and their control variables and boundarieshave been revised accordingly (Table 1) Figure 3shows the current status of the seven bounda-ries that can be quantified at the global level

Climate change

We retain the control variables and boundariesoriginally proposedmdashie an atmospheric CO2 con-centration of 350 parts per million (ppm) and anincrease in top-of-atmosphere radiative forcing of+10 W mndash2 relative to preindustrial levels (1)The radiative forcing control variable is the more

inclusive and fundamental although CO2 is im-portant because of its long lifetime in the atmo-sphere and the very large human emissionsHuman-driven changes to radiative forcing in-clude all anthropogenic factors CO2 other green-house gases aerosols and other factors thataffect the energy balance (18) Radiative forcingis generally the more stringent of the two bound-aries although the relationship between it andCO2 can vary through time with changes in therelative importance of the individual radiativeforcing factorsEvidence has accumulated to suggest that the

zone of uncertainty for the CO2 control variableshould be narrowed from 350 to 550 ppm to 350to 450 ppm CO2 (17 18) while retaining the cur-rent zone of uncertainty for radiative forcing of+10 to 15 W mndash2 relative to preindustrial levelsCurrent values of the control variables are 399ppmCO2 (annual average concentration for 2014) (34)and +23Wmndash2 (11 to 33Wmndash2) in 2011 relativeto 1750 (18) Observed changes in climate at cur-rent levels of the control variables confirm theoriginal choice of the boundary values and thenarrowing of the zone of uncertainty for CO2 Forexample there has already been an increase inthe intensity frequency and duration of heatwaves globally (35) the number of heavy rainfall

SCIENCE sciencemagorg 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 1259855-3

Fig 2The subglobal distributions and current status of the control variables for (A) biogeochemical flows of P (B) biogeochemical flows of N (C) land-system change and (D) freshwater use In each panel green areas are within the boundary (safe) yellow areas are within the zone of uncertainty (increasingrisk) and red areas are beyond the zone of uncertainty (high risk) Gray areas in (A) and (B) are areas where P and N fertilizers are not applied in (C) they areareas not covered by major forest biomes and in (D) they are areas where river flow is very low so that environmental flows are not allocated See Table 1 forvalues of the boundaries and their zones of uncertainty and (33) for more details on methods and results

RESEARCH | RESEARCH ARTICLE

1259855-4 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 sciencemagorg SCIENCE

Table 1 The updated control variables and their current values along with the proposed boundaries and zones of uncertainty for all nine planetaryboundaries In the first column the name for the Earth-system process used in the original PB publication (R2009 reference 1) is given for comparison

Earth-systemprocess

Controlvariable(s)

Planetary boundary(zone of uncertainty)

Current value ofcontrol variable

Climatechange(R2009same)

Atmospheric CO2

concentration ppm

Energy imbalanceat top-of-atmosphere W mndash2

350 ppm CO2 (350ndash450 ppm)

+10 W mndash2 (+10ndash15 W mndash2)

3985 ppm CO2

23 W mndash2

(11ndash33 W mndash2)

Change inbiosphereintegrity(R2009Rate ofbiodiversityloss)

Genetic diversityExtinction rate

Functional diversityBiodiversityIntactness Index (BII)

Note These areinterim controlvariables until moreappropriate ones aredeveloped

lt 10 EMSY (10ndash100 EMSY)but with an aspirational goal ofca 1 EMSY (the backgroundrate of extinction loss) EMSY =extinctions per million species-years

Maintain BII at 90 (90ndash30)or above assessedgeographically by biomeslargeregional areas (eg southernAfrica) major marineecosystems (eg coral reefs) orby large functional groups

100ndash1000 EMSY

84 applied tosouthern Africaonly

Stratosphericozonedepletion(R2009 same)

Stratospheric O3

concentration DUlt5 reduction from pre-industrial level of 290 DU(5ndash10) assessed bylatitude

Only transgressedover Antarctica inAustral spring(~200 DU)

Oceanacidification(R2009same)

Carbonate ionconcentrationaverage globalsurface oceansaturation state withrespect to aragonite(Warag)

ge80 of the pre-industrialaragonite saturation state ofmean surface ocean includingnatural diel and seasonalvariability (ge80ndash ge70)

~84 of thepre-industrialaragonitesaturation state

Biogeochemicalflows (P andN cycles)(R2009Biogeochemicalflows (interferencewith P and Ncycles))

P Global P flowfrom freshwatersystems into theocean

P Regional P flowfrom fertilizers toerodible soils

N Global Industrialand intentionalbiological fixationof N

11 Tg P yrndash1 (11ndash100 Tg P yrndash1)

62 Tg yrndash1 mined and applied toerodible (agricultural) soils(62-112 Tg yrndash1) Boundary is aglobal average but regionaldistribution is critical forimpacts

62 Tg N yrndash1 (62ndash82 Tg N yrndash1)Boundary acts as a globallsquovalversquo limiting introduction ofnew reactive N to Earth Systembut regional distribution offertilizer N is critical forimpacts

~22 Tg P yrndash1

~14 Tg P yrndash1

~150 Tg N yrndash1

RESEARCH | RESEARCH ARTICLE

events inmany regions of the world is increasing(17) changes in atmospheric circulation patternshave increased drought in some regions of theworld (17) and the rate of combined mass lossfrom the Greenland and Antarctic ice sheets isincreasing (36)

Changes in biosphere integrity

We propose a two-component approach address-ing two key roles of the biosphere in the Earthsystem The first captures the role of geneticallyunique material as the ldquoinformation bankrdquo thatultimately determines the potential for life to

continue to coevolve with the abiotic componentof the Earth system in the most resilient waypossible Genetic diversity provides the long-termcapacity of the biosphere to persist under andadapt to abrupt and gradual abiotic change Thesecond captures the role of the biosphere inEarth-system functioning through the value rangedistribution and relative abundance of the func-tional traits of the organisms present in an eco-system or biota (7)For the first role the concept of phylogenetic

species variability (PSV) (7 33 37) would be anappropriate control variable However because

global data are not yet available for PSV we re-tain the global extinction rate as an interim con-trol variable although it is measured inaccuratelyand with a time lag There may be a considerablerisk in using extinction rate as a control variablebecause phylogenetic (and functional) diversitymay be more sensitive to human pressures thanspecies-level diversity (38) In principle the bound-ary should be set at a rate of loss of PSV no greaterthan the rate of evolution of new PSV during theHolocene Because that is unknown wemust fallback on the (imperfectly) known extinction rateof well-studied organisms over the past several

SCIENCE sciencemagorg 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 1259855-5

Earth-systemprocess

Controlvariable(s)

Planetary boundary(zone of uncertainty)

Current value ofcontrol variable

Land-systemchange(R2009same)

Global Area offorested land as of original forestcover

Biome Area offorested land as of potential forest

Global 75 (75ndash54) Valuesare a weighted average of thethree individual biomeboundaries and their uncertaintyzones

BiomeTropical 85 (85ndash60)Temperate 50 (50ndash30)Boreal 85 (85ndash60)

62

Freshwateruse(R2009Globalfreshwateruse)

Global Maximumamount ofconsumptive bluewater use (km3yrndash1)

Basin Blue waterwithdrawal as ofmean monthly riverflow

Global 4000 km3 yrndash1

(4000ndash6000 km3 yrndash1)

Basin Maximum monthlywithdrawal as a percentageof mean monthly river flowFor low-flow months 25(25ndash55) for intermediate-flow months 30 (30ndash60)for high-flow months 55(55ndash85)

~2600 km3 yrndash1

Atmosphericaerosolloading(R2009same)

Global AerosolOptical Depth(AOD) but muchregional variation

Regional AOD asa seasonal averageover a region SouthAsian Monsoonused as a case study

Regional (South AsianMonsoon as a case study)anthropogenic total (absorbingand scattering) AOD overIndian subcontinent of 025(025ndash050) absorbing(warming) AOD less than 10of total AOD

030 AOD overSouth Asianregion

Introductionof novel entities(R2009 Chemicalpollution)

No control variablecurrently defined

No boundary currentlyidentified but see boundaryfor stratospheric ozone for anexample of a boundaryrelated to a novel entity (CFCs)

RESEARCH | RESEARCH ARTICLE

million yearsmdashabout 1 per million species-years(39)mdashand add a large uncertainty bound raisingthe boundary to 10 permillion species-years Therisk is that although the Earth system can tol-erate a higher-than-background level of extinc-tions for a time we do not knowwhat levels of ortypes of biodiversity lossmay possibly trigger non-linear or irreversible changes to the Earth systemThe second control variable aims to capture the

role of the biosphere in Earth-system functioningand measures loss of biodiversity components atboth global and biomelarge ecosystem levels Al-though several variables have been developed atlocal scales for measuring functional diversity[eg (40)] finding an appropriate control varia-ble at regional or global levels is challenging Forthe present we propose an interim control var-iable the Biodiversity Intactness Index (BII) (41)BII assesses change in population abundance as aresult of human impacts such as land or resourceuse across a wide range of taxa and functionalgroups at a biome or ecosystem level using pre-industrial era abundance as a reference point Theindex typically ranges from 100 (abundancesacross all functional groups at preindustrial levels)to lower values that reflect the extent and degreeof human modification of populations of plantsand animals BII values for particular functionalgroups can go above 100 if humanmodificationsto ecosystems lead to increases in the abundanceof those speciesDue to a lack of evidence on the relationship

between BII and Earth-system responses we pro-

pose a preliminary boundary at 90 of the BIIbut with a very large uncertainty range (90 to30) that reflects the large gaps in our knowl-edge about the BIIndashEarth-system functioningrelationship (42 43) BII has been so far appliedto southern Africarsquos terrestrial biomes only (seefig S3 for an estimation of aggregated humanpressures on the terrestrial biosphere globally)where the index (not yet disaggregated to func-tional groups) was estimated to be 84 BIIranged from 69 to 91 for the seven countrieswhere it has been applied (41) Observations acrossthese countries suggest that decreases in BII ad-equately capture increasing levels of ecosystemdegradation defined as land uses that do not al-ter the land-cover type but lead to a persistentloss in ecosystem productivity (41)In addition to further work on functional mea-

sures such as BII in the longer term the conceptof biome integritymdashthe functioning and persist-ence of biomes at broad scales (7)mdashoffers a prom-ising approach and with further research couldprovide a set of operational control variables (oneper biome) that is appropriate robust and scien-tifically based

Stratospheric ozone depletion

We retain the original control variable [O3 con-centration in DU (Dobson units)] and boundary(275 DU) This boundary is only transgressedover Antarctica in the austral spring when O3

concentration drops to about 200 DU (44) How-ever the minimum O3 concentration has been

steady for about 15 years and is expected to riseover the coming decades as the ozone hole isrepaired after the phasing out of ozone-depletingsubstances This is an example in which after aboundary has been transgressed regionally hu-manity has taken effective action to return theprocess back to within the boundary

Ocean acidification

This boundary is intimately linked with one ofthe control variables CO2 for the climate changePB The concentration of free H+ ions in the sur-face ocean has increased by about 30 over thepast 200 years due to the increase in atmosphericCO2 (45) This in turn influences carbonate chem-istry in surface ocean waters Specifically it lowersthe saturation state of aragonite (Warag) a form ofcalcium carbonate formed by many marine orga-nisms At Warag lt 1 aragonite will dissolve Nonew evidence has emerged to suggest that theoriginally proposed boundary (ge80 of the pre-industrial average annual global Warag) shouldbe adjusted although geographical heterogeneityin Warag is important in monitoring the state ofthe boundary around the worldrsquos oceans (fig S4)Currently Warag is approximately equal to 84 ofthe preindustrial value (46) This boundary wouldnot be transgressed if the climate-change bound-ary of 350 ppm CO2 were to be respected

Biogeochemical flows

The original boundary was formulated for phos-phorus (P) and nitrogen (N) only but we nowpropose a more generic PB to encompass humaninfluence on biogeochemical flows in general Al-though the carbon cycle is covered in the climate-change boundary other elements such as silicon(47 48) are also important for Earth-system func-tioning Furthermore there is increasing evidencethat ratios between elements in the environmentmay have impacts on biodiversity on land and inthe sea (49ndash51) Thus we may ultimately need todevelop PBs for other elements and their ratiosalthough for now we focus on P and N onlyA two-level approach is now proposed for the

P component of the biogeochemical flows bound-ary (see also the supplementary materials) Theoriginal global-level boundary based on the pre-vention of a large-scale ocean anoxic event isretained with the proposed boundary set at asustained flow of 11 Tg P yearndash1 from freshwatersystems into the ocean Based on the analysis ofCarpenter and Bennett (3) we now propose anadditional regional-level P boundary designedto avert widespread eutrophication of freshwatersystems at a flow of 62 Tg P yearndash1 from fer-tilizers (mined P) to erodible soilsGiven that the addition of P to regional

watersheds is almost entirely from fertilizers theregional-level boundary applies primarily to theworldrsquos croplands The current global rate of ap-plication of P in fertilizers to croplands is 142 TgP yearndash1 (52 53) Observations point toward a fewagricultural regions of very high P applicationrates as the main contributors to the transgres-sion of this boundary (Fig 2 and fig S5A) andsuggest that a redistribution of P from areas

1259855-6 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 sciencemagorg SCIENCE

Fig 3The current status of the control variables for seven of the nine planetary boundaries Thegreen zone is the safe operating space (below the boundary) yellow represents the zone of uncertainty(increasing risk) and red is the high-risk zoneThe planetary boundary itself lies at the inner heavy circleThe control variables have been normalized for the zone of uncertainty (between the two heavy circles)the center of the figure therefore does not represent values of 0 for the control variables The controlvariable shown for climate change is atmospheric CO2 concentration Processes for which global-levelboundaries cannot yet be quantified are represented by gray wedges these are atmospheric aerosolloading novel entities and the functional role of biosphere integrity Modified from (1)

RESEARCH | RESEARCH ARTICLE

where it is currently in excess to areas where thesoil is naturally P-poormay simultaneously boostglobal crop production and reduce the transgres-sion of the regional-level P boundary (3 52 54)The N boundary has been taken from the com-

prehensive analysis of de Vries et al (5) whichproposed a PB for eutrophication of aquatic eco-systems of 62 Tg N yearndash1 from industrial andintentional biological N fixation using the moststringent water quality criterion As for the Pboundary a few agricultural regions of very highN application rates are the main contributors tothe transgression of this boundary (Fig 2 andfig S5B) This suggests that a redistribution of Ncould simultaneously boost global crop produc-tion and reduce the transgression of the regional-level boundaryBecause the major anthropogenic perturba-

tion of both the N and P cycles arises from fertil-izer application we can analyze the links betweenthe independently determined N and P bounda-ries in an integrated way based on the NP ratioin the growing plant tissue of agricultural cropsApplying this ratio which is on average 118 (55)to the P boundary (62 Tg P yearndash1) gives an Nboundary of 73 Tg N yearndash1 Conversely applyingthe ratio to theN boundary (62 TgN yearndash1) givesa P boundary of 53 Tg P yearndash1 The small dif-ferences between the boundaries derived usingthe NP ratio and those calculated independent-ly which are likely nonsignificant differencesgiven the precision of the data available for thecalculations show the internal consistency inour approach to the biogeochemical boundariesMore detail on the development of the P andN

boundaries is given in (33) where we also em-phasize that the proposed P and N boundariesmay be larger for an optimal allocation of N (andP) over the globe

Land-system change

The updated biosphere integrity boundary pro-vides a considerable constraint on the amountand pattern of land-system change in all ter-restrial biomes forests woodlands savannasgrasslands shrublands tundra and so on Theland-system change boundary is now focusedmore tightly on a specific constraint the biogeo-physical processes in land systems that directlyregulate climatemdashexchange of energy water andmomentum between the land surface and theatmosphere The control variable has been changedfrom the amount of cropland to the amount offorest cover remaining as the three major forestbiomesmdashtropical temperate and borealmdashplay astronger role in land surfacendashclimate couplingthan other biomes (56 57) In particular we fo-cus on those land-system changes that can in-fluence the climate in regions beyond the regionwhere the land-system change occurredOf the forest biomes tropical forests have sub-

stantial feedbacks to climate through changes inevapotranspiration when they are converted tononforested systems and changes in the distribu-tion of boreal forests affect the albedo of the landsurface and hence regional energy exchange Bothhave strong regional and global teleconnections

The biome-level boundary for these two types offorest have been set at 85 (Table 1 and thesupplementary materials) and the boundary fortemperate forests has been proposed at 50 ofpotential forest cover because changes to tem-perate forests are estimated to have weaker in-fluences on the climate system at the global levelthan changes to the other two major forestbiomes (56) These boundaries would almostsurely be met if the proposed biosphere integ-rity boundary of 90 BII were respectedEstimates of the current status of the land-

system change boundary are given in Figs 2 and3 and fig S6 and in (58)

Freshwater use

The revised freshwater use boundary has retainedconsumptive use of blue water [from rivers lakesreservoirs and renewable groundwater stores(59)] as the global-level control variable and4000 km3year as the value of the boundaryThis PB may be somewhat higher or lower de-pending on riversrsquo ecological flow requirements(6) Therefore we report here a new assessmentto complement the PB with a basin-scale bound-ary for the maximum rate of blue water with-drawal along rivers based on the amount of waterrequired in the river system to avoid regime shiftsin the functioning of flow-dependent ecosystemsWe base our control variable on the concept ofenvironmental water flows (EWF) which definesthe level of river flows for different hydrologicalcharacteristics of river basins adequate to main-tain a fair-to-good ecosystem state (60ndash62)The variable monthly flow (VMF) method

(33 63) was used to calculate the basin-scaleboundary for water This method takes accountof intra-annual variability by classifying flow re-gimes into high- intermediate- and low-flowmonths and allocating EWF as a percentage ofthe mean monthly flow (MMF) Based on thisanalysis the zones of uncertainty for the river-basin scale water boundary were set at 25 to 55of MMF for the low-flow regime 40 to 70 forthe intermediate-flow regime and 55 to 85 forthe high-flow regime (table S2) The boundarieswere set at the lower end of the uncertaintyranges that encompass average monthly EWFOur new estimates of the current status of thewater use boundarymdashcomputed based on gridcellndashspecific estimates of agricultural industrialand domestic water withdrawalsmdashare shown inFigs 2 and 3 with details in figs S7 and S8

Atmospheric aerosol loading

Aerosols have well-known serious human healtheffects leading to about 72 million deaths peryear (64) They also affect the functioning of theEarth system in many ways (65) (fig S9) Herewe focus on the effect of aerosols on regionalocean-atmosphere circulation as the rationalefor a separate aerosols boundary We adopt aero-sol optical depth (AOD) (33) as the control var-iable and use the south Asian monsoon as a casestudy based on the potential of widespread aero-sol loading over the Indian subcontinent to switchthe monsoon system to a drier state

The background AOD over south Asia is ~015and can be as high as 04 during volcanic events(66) Emissions of black carbon and organic car-bon from cooking and heating with biofuels andfrom diesel transportation and emission of sul-fates and nitrates from fossil fuel combustioncan increase seasonal mean AODs to as high as04 (larger during volcanic periods) leading todecreases of 10 to 15 of incident solar radiationat the surface (fig S9) A substantial decrease inmonsoon activity is likely around an AOD of 050an increase of 035 above the background (67)Taking a precautionary approach toward uncer-tainties surrounding the position of the tippingpoint we propose a boundary at an AOD of 025(an increase due to human activities of 01) witha zone of uncertainty of 025 to 050 The annualmean AOD is currently about 03 (66) within thezone of uncertainty

Introduction of novel entities

We define novel entities as new substances newforms of existing substances and modified lifeforms that have the potential for unwanted geo-physical andor biological effects Anthropogenicintroduction of novel entities to the environmentis of concern at the global level when these en-tities exhibit (i) persistence (ii) mobility acrossscales with consequent widespread distributionsand (iii) potential impacts on vital Earth-systemprocesses or subsystems These potentially in-clude chemicals and other new types of engi-neered materials or organisms [eg (68ndash71)] notpreviously known to the Earth system as well asnaturally occurring elements (for example heavymetals) mobilized by anthropogenic activitiesThe risks associated with the introduction ofnovel entities into the Earth system are exempli-fied by the release of CFCs (chlorofluorocarbons)which are very useful synthetic chemicals thatwere thought to be harmless but had unexpecteddramatic impacts on the stratospheric ozone layerIn effect humanity is repeatedly running suchglobal-scale experiments but not yet applying theinsights from previous experience to new appli-cations (72 73)Today there aremore than 100000 substances

in global commerce (74) If nanomaterials andplastic polymers that degrade to microplasticsare included the list is even longer There is alsoa ldquochemical intensificationrdquo due to the rapidlyincreasing global production of chemicals theexpanding worldwide distribution as chemicalproducts or in consumer goods and the exten-sive global trade in chemical wastes (75)In recent years there has been a growing de-

bate about the global-scale effects of chemicalpollution leading to calls for the definition ofcriteria to identify the kinds of chemical sub-stances that are likely to be globally problematic(76 77) Persson et al (73) proposed that there arethree conditions that need to be fulfilled for achemical to pose a threat to the Earth system (i)the chemical has an unknown disruptive effecton a vital Earth-systemprocess (ii) the disruptiveeffect is not discovered until it is a problem at theglobal scale and (iii) the effect is not readily

SCIENCE sciencemagorg 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 1259855-7

RESEARCH | RESEARCH ARTICLE

reversible The challenge to the research commu-nity is to develop the knowledge base that allowsthe screening of chemicals before they are re-leased into the environment for properties thatmay predispose them toward becoming globalproblemsAs a first step toward meeting this challenge

the three conditions outlined above have beenused as the basis for identifying scenarios ofchemical pollution that fulfill the conditions andas a next step for pinpointing chemical profilesthat fit the scenarios (28) This proposal consti-tutes a first attempt at adding the Earth-systemperspective when assessing hazard and risk ofchemicals and offers a vision for a systematic ap-proach to a complex management situation withmany unknownsDespite this progress in developing an Earth-

systemndashoriented approach there is not yet anaggregate global-level analysis of chemical pol-lution on which to base a control variable or aboundary value It may also serve little purposeto define boundary values and control varia-bles for a planetary boundary of this complexityNevertheless there is a potential threat fromnovel entities to disrupt the functioning of theEarth-system and society needs to learn how tomitigate these unknown risks and manage chem-icals under uncertainty (28 73)Some precautionary and preventive actions

can be considered These may include a strongerfocus on green chemistry (78) finding synergieswith risk-reducing interventions in other fieldssuch as occupational health (79) paying moreattention to learning from earlier mistakes (8081) and investing in science to better under-stand and monitor vital Earth-system processesin order to be able to detect disruptive effectsfrom novel entities as early as possible

Hierarchy of boundaries

An analysis of the many interactions among theboundaries (table S3 and fig S10) suggests thattwo of themmdashclimate change and biosphereintegritymdashare highly integrated emergent system-level phenomena that are connected to all of theother PBs They operate at the level of the wholeEarth system (7) and have coevolved for nearly4 billion years (82) They are regulated by theother boundaries and on the other hand pro-vide the planetary-level overarching systems with-in which the other boundary processes operateFurthermore large changes in the climate or inbiosphere integrity would likely on their ownpush the Earth system out of the Holocene stateIn fact transitions between time periods in Earthhistory have often been delineated by substantialshifts in climate the biosphere or both (82 83)These observations suggest a two-level hierar-

chy of boundaries in which climate change andbiosphere integrity should be recognized as coreplanetary boundaries through which the otherboundaries operate The crossing of one or moreof the other boundaries may seriously affect hu-man well-being and may predispose the trans-gression of a core boundary(ies) but does not byitself lead to a new state of the Earth system This

hierarchical approach to classifying the bounda-ries becomes clearer by examining inmore detailthe roles of climate and biosphere integrity in thefunctioning of the Earth systemThe climate system is a manifestation of the

amount distribution and net balance of energyat Earthrsquos surface The total amount of energysets the overall conditions for life In Earthrsquos cur-rent climate a range of global surface temper-atures and atmospheric pressures allows the threephases of water to be present simultaneouslywith ice and water vapor playing critical roles inthe physical feedbacks of the climate system Thedistribution of energy by latitude over the landand sea surfaces and within the ocean plays amajor role in the circulation of the two greatfluids the ocean and the atmosphere These sys-temic physical characteristics are key spatial de-terminants of the distribution of the biota andthe structure and functioning of ecosystems andare controllers of biogeochemical flowsBiosphere integrity is also crucial to Earth-

system functioning where the biosphere is de-fined as the totality of all ecosystems (terrestrialfreshwater andmarine) on Earth and their biota(32) These ecosystems and biota play a criticalrole in determining the state of the Earth systemregulating its material and energy flows and itsresponses to abrupt and gradual change (7) Di-versity in the biosphere provides resilience toterrestrial and marine ecosystems (83 84) Thebiosphere not only interacts with the other plan-etary boundaries but also increases the capacityof theEarth system topersist in a given state underchanges in these other boundaries The ultimatebasis for the many roles that the biosphere playsin Earth-system dynamics is the genetic code ofthe biota the basic information bank that de-fines the biospherersquos functional role and its ca-pacity to innovate and persist into the future

Planetary boundaries in asocietal context

A proposed approach for sustainable develop-ment goals (SDGs) (85) argues that the stablefunctioning of the Earth system is a prereq-uisite for thriving societies around the world Thisapproach implies that the PB framework orsomething like it will need to be implementedalongside the achievement of targets aimed atmore immediate human needs such as provi-sion of clean affordable and accessible energyand the adequate supply of food World devel-opment within the biophysical limits of a stableEarth system has always been a necessity [eg(86 87)] However only recently for a numberof reasons has it become possible to identifyevaluate and quantify risks of abrupt planetary-and biome-level shifts due to overshoot of keyEarth-system parameters (i) the emergence ofglobal-change thinking and Earth-system think-ing (88) (ii) the rise of ldquothe Planetaryrdquo as a rel-evant level of complex system understanding(89ndash92) and (iii) observable effects of the rapidincrease in human pressures on the planet (16)The PB approach is embedded in this emerg-

ing social context but it does not suggest how to

maneuver within the safe operating space in thequest for global sustainability For example thePB framework does not as yet account for the re-gional distribution of the impact or its histor-ical patterns Nor does the PB framework takeinto account the deeper issues of equity and cau-sation The current levels of the boundary pro-cesses and the transgressions of boundaries thathave already occurred are unevenly caused bydifferent human societies and different socialgroups The wealth benefits that these trans-gressions have brought are also unevenly distrib-uted socially and geographically It is easy toforesee that uneven distribution of causation andbenefits will continue and these differentialsmust surely be addressed for a Holocene-likeEarth-system state to be successfully legitimatedand maintained However the PB framework ascurrently construed provides no guidance as tohow this may be achieved [although some po-tential synergies have been noted (54)] and itcannot readily be used tomake choices betweenpathways for piecemeal maneuvering withinthe safe operating space ormore radical shifts ofglobal governance (93)The nature of the PB framework implies that

two important cautions should be observedwhenapplication of the framework to policy or man-agement is proposed boundary interactions andscale

Boundary interactions

The planetary boundaries framework arises fromthe scientific evidence that Earth is a singlecomplex integrated systemmdashthat is the bound-aries operate as an interdependent set [eg(94)] (table S1 and fig S10) Although a system-atic quantitative analysis of interactions amongall of the processes for which boundaries areproposed remains beyond the scope of currentmodeling and observational capacity the Earthsystem clearly operates in well-defined states inwhich these processes and their interactionscan create stabilizing or destabilizing feedbacks(16 90 95) This has profound implications forglobal sustainability because it emphasizes theneed to address multiple interacting environ-mental processes simultaneously (eg stabilizingthe climate system requires sustainable forestmanagement and stable ocean ecosystems)

Scale

The PB framework is not designed to be ldquodown-scaledrdquo or ldquodisaggregatedrdquo to smaller levels suchas nations or local communities That said thePB framework recognizes the importance ofchanges at the level of subsystems in the Earthsystem (eg biomes or large river basins) on thefunctioning of the Earth system as a whole Alsothere are strong arguments for an integrated ap-proach coupling boundary definitions at region-al and global levels with development goals toenable the application of ldquoPB thinkingrdquo at lev-els (nations basins and regions) where policyaction most commonly occurs [eg (85 96)]This update of the PB framework is one step on

a longer-term evolution of scientific knowledge to

1259855-8 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 sciencemagorg SCIENCE

RESEARCH | RESEARCH ARTICLE

inform and support global sustainability goalsand pathways This evolution is needed morethan ever before there are severe implementa-tion gaps inmany global environmental policiesrelating to the PB issues where problematictrends are not being halted or reversed despiteinternational consensus about the urgency of theproblems The prospect of tighter resource con-straints and rising environmental hazards is alsounavoidably turning the focus onto global socialequity and the planetary stewardship of Earthrsquoslife-support system There is a need for a trulyglobal evidence base with much greater integra-tion among issues in order to respond to theseglobal challenges New research initiatives [egFuture Earth (wwwfutureearthorg)] provide evi-dence that science can respond to this need byapplying Earth-system research to advance a newgeneration of integrated global analyses and toexplore options for transformations toward sus-tainability This is a clear sign that as the risksof the Anthropocene to human well-being be-come clearer research is maturing to a pointwhere a systemic step-change is possiblemdashandnecessarymdashin exploring and defining a safe andjust planetary operating space for the furtherdevelopment of human societies

Methods summary

Our approach to building the planetary bound-aries framework is described above We haveimplemented the framework through an ex-pert assessment and synthesis of the scientificknowledge of intrinsic biophysical processes thatregulate the stability of the Earth system Ourprecautionary approach is based on the main-tenance of a Holocene-like state of the Earthsystem and on an assessment of the level ofhuman-driven change that would risk destabi-lizing this state For the climate change PB thereis already much literature on which to basesuch an assessment For others such as strato-spheric ozone ocean acidification extinctionrates and P andN cycles we have used estimatesof preindustrial values of the control variableas a Holocene baseline Where large undesira-ble thresholds exist and have been studied (egpolar ice sheets Amazon rainforest aragonitedissolution atmospheric aerosols and the southAsian monsoon) quantitative boundaries can bereadily proposed For others where the focus ison erosion of Earth-system resilience the bound-aries are more difficult (but not impossible) toquantify as reflected in larger uncertainty zonesWe used large-scale assessments of the impacts

of human activities on Earth-system functioning[eg Intergovernmental Panel on Climate Change(17 18) the International Geosphere-BiosphereProgramme synthesis (16) and chemicals (75 80)]as sources of community-level understandingon which to propose PBs Our update has alsorelied on post-2009 assessments of individualboundaries by the relevant expert research com-munities examples include phosphorus (3) ni-trogen (5) biosphere integrity (7) freshwater use(5 63) and novel entities [with a focus on chem-icals (28 73)] Finally some new analyses have

been undertaken specifically for this paper (i) afreshwater-use PB based on the EWF approach(33 63) (ii) the linkage of the phosphorus andnitrogen boundaries via the NP ratio in grow-ing crop tissue (33) and (iii) the use of majorforest biomes as the basis for the land-systemchange PB (33)

REFERENCES AND NOTES

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2 J Rockstroumlm et al A safe operating space for humanityNature 461 472ndash475 (2009) doi 101038461472apmid 19779433

3 S R Carpenter E M Bennett Reconsideration of theplanetary boundary for phosphorus Environ Res Lett 6014009 (2011) doi 1010881748-932661014009

4 S W Running Ecology A measurable planetary boundaryfor the biosphere Science 337 1458ndash1459 (2012)doi 101126science1227620 pmid 22997311

5 W de Vries J Kros C Kroeze S P Seitzinger Assessingplanetary and regional nitrogen boundaries related to foodsecurity and adverse environmental impacts Curr OpinionEnviron Sust 5 392ndash402 (2013) doi 101016jcosust201307004

6 D Gerten et al Towards a revised planetary boundary forconsumptive freshwater use Role of environmental flowrequirements Curr Opinion Environ Sust 5 551ndash558 (2013)doi 101016jcosust201311001

7 G M Mace et al Approaches to defining a planetary boundaryfor biodiversity Glob Environ Change 28 289ndash297 (2014)doi 101016jgloenvcha201407009

8 V Galaz Global Environmental Governance Technology andPolitics The Anthropocene Gap (Edward Elgar CheltenhamUK 2014)

9 UN GSP (UN High-Level Panel on Global Sustainability)Resilient People Resilient Planet A Future Worth Choosing(Report for the 2012 Rio+20 Earth Summit United NationsNew York 2012)

10 WBCSD (World Business Council on Sustainable Development)Action 2020 Overview (WBCSD Geneva Switzerlandhttpaction2020org accessed 18 June 2014)

11 R Costanza L Graumlich W Steffen Eds Integrated Historyand Future of People on Earth (MIT Press CambridgeMA USA 2006)

12 S Soumlrlin P Warde in Naturersquos End History and theEnvironment S Soumlrlin P Warde Eds (Palgrave MacMillanLondon 2009) pp 1ndash19

13 R C Bishop Endangered species and uncertainty Theeconomics of a safe minimum standard Am J Agric Econ 6110ndash18 (1978) doi 1023071240156

14 T M Crowards Safe minimum standards Costs andopportunities Ecol Econ 25 303ndash314 (1998) doi 101016S0921-8009(97)00041-4

15 W Steffen J Crutzen J R McNeill The Anthropocene Arehumans now overwhelming the great forces of NatureAmbio 36 614ndash621 (2007) doi 1015790044-7447(2007)36[614TAAHNO]20CO2 pmid 18240674

16 W Steffen et al Global Change and the Earth System A PlanetUnder Pressure (The IGBP Book Series Springer-VerlagBerlin Heidelberg New York 2004)

17 IPCC (Intergovernmental Panel on Climate Change) Managingthe risks of extreme events and disasters to advanceclimate change adaptation A special report of Working GroupsI and II of the IPCC CB Field et al Eds (CambridgeUniversity Press Cambridge UK (2012) doi 101017CBO9781139177245

18 IPCC (Intergovernmental Panel on Climate Change) ClimateChange 2013 The Physical Science Basis Summary forPolicymakers L Alexander et al Eds (IPCC SecretariatGeneva Switzerland 2013) doi 101017CBO9781107415324

19 P J Crutzen Geology of mankind Nature 415 23 (2002)doi 101038415023a pmid 11780095

20 K Richardson W Steffen D Liverman Climate Change GlobalRisks Challenges and Decisions (Cambridge Univ PressCambridge UK 2011)

21 T M Lenton et al Tipping elements in the Earthrsquos climatesystem Proc Natl Acad Sci USA 105 1786ndash1793 (2008)doi 101073pnas0705414105 pmid 18258748

22 M Scheffer et al Early-warning signals for criticaltransitions Nature 461 53ndash59 (2009) doi 101038nature08227 pmid 19727193

23 S R Carpenter W A Brock Rising variance A leadingindicator of ecological transition Ecol Lett 9 311ndash318 (2006)doi 101111j1461-0248200500877x pmid 16958897

24 J Bakke et al Rapid oceanic and atmospheric changes duringthe Younger Dryas cold period Nat Geosci 2 202ndash205(2009) doi 101038ngeo439

25 M Scheffer et al Anticipating critical transitions Science338 344ndash348 (2012) doi 101126science1225244pmid 23087241

26 R Wang et al Flickering gives early warning signals of acritical transition to a eutrophic lake state Nature 492419ndash422 (2012) doi 101038nature11655 pmid 23160492

27 R Biggs S R Carpenter W A Brock Turning back fromthe brink Detecting an impending regime shift in time to avertit Proc Natl Acad Sci USA 106 826ndash831 (2009)doi 101073pnas0811729106 pmid 19124774

28 M MacLeod et al Identifying chemicals that are planetaryboundary threats Environ Sci Technol 48 11057ndash11063(2014) doi 101021es501893m pmid 25181298

29 C S Holling Resilience and stability of ecological systemsAnnu Rev Ecol Syst 4 1ndash23 (1973) doi 101146annureves04110173000245

30 C Folke et al Resilience thinking Integrating resilienceadaptability and transformability Ecol Soc 15 20 (2010)wwwecologyandsocietyorgvol15iss4art20

31 T P Hughes S Carpenter J Rockstroumlm M SchefferB Walker Multiscale regime shifts and planetary boundariesTrends Ecol Evol 28 389ndash395 (2013) doi 101016jtree201305019 pmid 23769417

32 T M Lenton H T P Williams On the origin of planetary-scaletipping points Trends Ecol Evol 28 380ndash382 (2013)doi 101016jtree201306001 pmid 23777818

33 Supplementary text figures and tables are available onScience Online

34 NOAA (National Oceanic and Atmospheric Administration)NOAA-ESRL Annual CO2 Data accessed at httpco2noworgCurrent-CO2CO2-Nowannual-co2html (2014)

35 S E Perkins L V Alexander J Nairn Increasing frequencyintensity and duration of observed global heat waves and warmspells Geophys Res Lett 39 L20714 (2012) doi 1010292012GL053361

36 A Shepherd et al A reconciled estimate of ice-sheet massbalance Science 338 1183ndash1189 (2012) doi 101126science1228102 pmid 23197528

37 M R Helmus T J Bland C K Williams A R IvesPhylogenetic measures of biodiversity Am Nat 169 E68ndashE83(2007) doi 101086511334 pmid 17230400

38 S Drsquoagata et al Human-mediated loss of phylogeneticand functional diversity in coral reef fishes Curr Biol24 555ndash560 (2014) doi 101016jcub201401049pmid 24560574

39 A D Barnosky et al Has the Earthrsquos sixth mass extinctionalready arrived Nature 471 51ndash57 (2011) doi 101038nature09678 pmid 21368823

40 N W Mason F de Bello D Mouillot S Pavoine S Dray Aguide for using functional diversity indices to reveal changesin assembly processes along ecological gradients J VegSci 24 794ndash806 (2013) doi 101111jvs12013

41 R J Scholes R Biggs A biodiversity intactness index Nature434 45ndash49 (2005) doi 101038nature03289pmid 15744293

42 B Cardinale Ecology Impacts of biodiversity loss Science336 552ndash553 (2012) doi 101126science1222102pmid 22556243

43 D U Hooper et al A global synthesis reveals biodiversityloss as a major driver of ecosystem change Nature 486105ndash108 (2012) doi 101038nature11118pmid 22678289

44 BAS (British Antarctic Survey) ldquoAntarctic ozonerdquo wwwantarcticaacukmetjdsozoneindexhtmldata J ShanklinBritish Antarctic Survey (2013)

45 Royal Society Ocean Acidification Due to IncreasingAtmospheric Carbon Dioxide Policy Document 1205 (TheRoyal Society London 2005)

46 J M Guinotte V J Fabry Ocean acidification and its potentialeffects on marine ecosystems Ann N Y Acad Sci 1134320ndash342 (2008) doi 101196annals1439013pmid 18566099

47 D J Conley Terrestrial ecosystems and the globalbiogeochemical silica cycle Global Biogeochem Cycles 16681ndash688 (2002) doi 1010292002GB001894

SCIENCE sciencemagorg 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 1259855-9

RESEARCH | RESEARCH ARTICLE

48 F Vandevenne E Struyf W Clymans P Meire Agriculturalsilica harvest Have humans created a new loop in the globalsilica cycle Front Ecol Environ 10 243ndash248 (2012)doi 101890110046

49 S E Gress T D Nichols C C Northcraft W T PeterjohnNutrient limitation in soils exhibiting differing nitrogenavailabilities What lies beyond nitrogen saturation Ecol 88119ndash130 (2007) doi 1018900012-9658(2007)88[119NLISED]20CO2 pmid 17489460

50 H Hillebrand V Lehmpfuhl Resource stoichiometry andconsumers control the biodiversity-productivity relationship inpelagic metacommunities Am Nat 178 171ndash181 (2011)doi 101086660831 pmid 21750381

51 C M Moore et al Processes and patterns of oceanic nutrientlimitation Nat Geosci 6 701ndash710 (2013) doi 101038ngeo1765

52 G K MacDonald E M Bennett P A Potter N RamankuttyAgronomic phosphorus imbalances across the worldrsquoscroplands Proc Natl Acad Sci USA 108 3086ndash3091 (2011)doi 101073pnas1010808108 pmid 21282605

53 L Bouwman et al Exploring global changes in nitrogen andphosphorus cycles in agriculture induced by livestockproduction over the 1900-2050 period Proc Natl AcadSci USA 110 20882ndash20887 (2013) doi 101073pnas1012878108 pmid 21576477

54 W Steffen M Stafford Smith Planetary boundaries equityand global sustainability Why wealthy countries could benefitfrom more equity Curr Opinion Environ Sust 5 403ndash408(2013) doi 101016jcosust201304007

55 D J Greenwood et al A unifying concept for the dependenceof whole-crop N P ratio on biomass theory and experimentAnn Bot (Lond) 102 967ndash977 (2008) doi 101093aobmcn188 pmid 18840873

56 P K Snyder C Delire J A Foley Evaluating the influence ofdifferent vegetation biomes on the global climate Clim Dyn23 279ndash302 (2004) doi 101007s00382-004-0430-0

57 P C West G T Narisma C C Barford C J KucharikJ A Foley An alternative approach for quantifying climateregulation by ecosystems Front Ecol Environ 9 126ndash133(2010) doi 101890090015

58 EPI (Earth Policy Institute) ldquoForest coverrdquo wwwearthpolicyorgindicatorsC56forests_2012_ (2014)

59 M Falkenmark Meeting water requirements of an expandingworld population Philos Trans R Soc Lond B Biol Sci 352929ndash936 (1997) doi 101098rstb19970072

60 J S Wallace M C Acreman C A Sullivan The sharing ofwater between society and ecosystems From conflict tocatchment-based co-management Philos Trans R Soc LondB Biol Sci 358 2011ndash2026 (2003) doi 101098rstb20031383 pmid 14728795

61 N L Poff et al The natural flow regime A paradigm for riverconservation and restoration BioSci 47 769ndash784 (1997)doi 1023071313099

62 N L Poff J K H Zimmerman Ecological responses to alteredflow regimes A literature review to inform the science andmanagement of environmental flows Biol 55 194ndash205 (2010)doi 101111j1365-2427200902272x

63 A V Pastor F Ludwig H Biemans H Hoff P KabatAccounting for environmental flow requirements in globalwater assessments Hydrol Earth Syst Sci 18 5041ndash5059(2014) doi 105194hess-18-5041-2014

64 WHO (World Health Organization) Burden of Disease from theJoint Effects of Household and Ambient Air Pollution for 2012(wwwwhointphehealth_topicsoutdoorairdatabasesFINAL_HAP_AAP_BoD24March2014pdf accessed 23 June 2014httpwwwwhointphehealth_topicsoutdoorairdatabasesen)

65 O Boucher et al in Climate Change 2013 The Physical ScienceBasis IPCC AR5 WGI report T Stocker et al Eds (CambridgeUniv Press Cambridge UK 2013) chap 7 pp 571ndash657

66 M Chin et al Multi-decadal aerosol variations from 1980 to2009 A perspective from observations and a global modelAtmos Chem Phys 14 3657ndash3690 (2014) doi 105194acp-14-3657-2014

67 V Ramanathan et al Atmospheric brown clouds Impacts onSouth Asian climate and hydrological cycle Proc Natl AcadSci USA 102 5326ndash5333 (2005) doi 101073pnas0500656102 pmid 15749818

68 M Cole P Lindeque C Halsband T S Galloway Microplasticsas contaminants in the marine environment A review MarPollut Bull 62 2588ndash2597 (2011) doi 101016jmarpolbul201109025 pmid 22001295

69 EEA (European Environment Agency) Genetically ModifiedOrganisms (GMOs) The Significance of Gene Flow ThroughPollen Transfer (Environmental Issue Report 28 EuropeanEnvironment Agency Copenhagen Denmark 2002)

70 J A Ivar do Sul M F Costa The present and future ofmicroplastic pollution in the marine environment Environ Pollut185 352ndash364 (2014) doi 101016jenvpol201310036pmid 24275078

71 R Kessler Engineered nanoparticles in consumer productsUnderstanding a new ingredient Environ Health Perspect 119a120ndasha125 (2011) doi 101289ehp119-a120 pmid 21356630

72 M Rees Our Final Century Will Civilisation Survive theTwenty-first Century (Arrow Books London 2003)

73 L M Persson et al Confronting unknown planetary boundarythreats from chemical pollution Environ Sci Technol 4712619ndash12622 (2013) doi 101021es402501c pmid 23980998

74 P P Egeghy et al The exposure data landscape formanufactured chemicals Sci Total Environ 414 159ndash166(2012) doi 101016jscitotenv201110046 pmid 22104386

75 UNEP (United Nations Environment Programme) GCOGlobal Chemicals Outlook Towards Sound Management ofChemicals (United Nations Environment ProgrammeNairobi Kenya 2013)

76 S Strempel M Scheringer C A Ng K HungerbuumlhlerScreening for PBT chemicals among the ldquoexistingrdquo andldquonewrdquo chemicals of the EU Environ Sci Technol 465680ndash5687 (2012) doi 101021es3002713pmid 22494215

77 M Scheringer et al How many persistent organic pollutantsshould we expect Atmos Poll Res 3 383ndash391 (2012)doi 105094APR2012044

78 K Sanderson Chemistry Itrsquos not easy being green Nature469 18ndash20 (2011) doi 101038469018a pmid 21209638

79 P A Schulte et al Occupational safety and health greenchemistry and sustainability A review of areas ofconvergence Environ Health 12 31 (2013) doi 1011861476-069X-12-31 pmid 23587312

80 EEA (European Environment Agency) Late Lessons from EarlyWarnings The Precautionary Principle 1896-2000 (EnvironmentalIssue Report 222001 Copenhagen Denmark 2001)

81 D Gee Late lessons from early warnings Toward realism andprecaution with endocrine-disrupting substances EnvironHealth Perspect 114 (suppl 1) 152ndash160 (2006) doi 101289ehp8134 pmid 16818262

82 T Lenton A Watson A Revolutions That Made the Earth(Oxford Univ Press Oxford UK 2011)

83 R Biggs et al Toward principles for enhancing the resilienceof ecosystem services Annu Rev Environ Resour 37421ndash448 (2012) doi 101146annurev-environ-051211-123836

84 G S Cumming P Olsson F S Chapin III C S HollingResilience experimentation and scale mismatches in social-ecological systems Landscape Ecol 28 1139ndash1150 (2013)doi 101007s10980-012-9725-4

85 D Griggs et al Policy Sustainable development goals forpeople and planet Nature 495 305ndash307 (2013) doi 101038495305a pmid 23518546

86 R Costanza Ed Ecological Economics The Science andManagement of Sustainability (Columbia Univ PressNew York 1991)

87 C Folke in Linking the Natural Environment and the EconomyEssays from the Eco-Eco Group C Folke T Karingberger Eds(Kluwer Academic Publishers Dordrecht Netherlands 1991)pp 77ndash94

88 L Robin S Soumlrlin P Warde Eds The Future of NatureDocuments of Global Change (Yale Univ Press New Haven CT2013)

89 U Heise Sense of Place and Sense of Planet TheEnvironmental Imagination of the Global (Oxford Univ PressOxford 2008)

90 M Scheffer Critical Transitions in Nature and Society(Princeton Univ Press Princeton NJ 2009)

91 J Masco Bad weather On planetary crisis Soc Stud Sci 407ndash40 (2010) doi 1011770306312709341598

92 G Paacutelsson et al Reconceptualizing the lsquoAnthroposrsquo in theAnthropocene Integrating the social sciences and humanitiesin global environmental change research Environ Sci Policy28 4 (2013) doi 101016jenvsci201211004

93 N Castree et al Changing the intellectual climate NatureClim Change 4 763ndash768 (2014) doi 101038nclimate2339

94 J M Anderies S R Carpenter W Steffen J Rockstroumlm Thetopology of non-linear global carbon dynamics From tippingpoints to planetary boundaries Environ Res Lett 8 044048(2013) doi 1010881748-932684044048

95 S E Cornell I C Prentice J I House C J DownyUnderstanding the Earth System Global Change Science forApplication (Cambridge Univ Press Cambridge 2012)

96 J A Dearing et al Safe and just operating spaces for regionalsocial-ecological systems Glob Environ Change 28 227ndash238(2014) doi 101016jgloenvcha201406012

ACKNOWLEDGMENTS

We thank J Foley and N Ramunkutty for contributions to theland-system change boundary A Pastor for analytical work on thePB for freshwater B Armstrong C Butler T McMichael andA Woodward for contributions to the novel entities boundary andB Scholes for comments on an earlier version of the manuscriptData associated with the paper are located at the StockholmResilience Centre Sweden (httpwwwstockholmresilienceorg21researchresearch-programmesplanetary-boundarieshtml)The planetary boundaries research at the Stockholm ResilienceCentre is made possible through a core grant from MISTRA(Swedish Foundation for Strategic Environmental Research) SECis supported by the Swedish Research Council EMB is supportedby the Natural Sciences and Engineering Research Council ofCanada and by the Trottier Institute for Science and Public PolicyRB is supported by a Branco Weiss Fellowship CF is supportedby the Family Erling Persson Academy Programme on GlobalEconomic Dynamics and the Biosphere IF is supported by theStordalen Foundation (Norway) SS is supported by theRiksbanken Jubileumsfond and the Institute for Advanced StudyPrinceton NJ and SRC and VR are supported bythe US National Science Foundation

SUPPLEMENTARY MATERIALS

wwwsciencemagorgcontent34762231259855supplDC1MethodsFigs S1 to S10Tables S1 to S3References (97ndash158)

11 August 2014 accepted 8 January 2015Published online 15 January 2015101126science1259855

1259855-10 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 sciencemagorg SCIENCE

RESEARCH | RESEARCH ARTICLE

DOI 101126science1259855 (2015)347 Science

et alWill SteffenplanetPlanetary boundaries Guiding human development on a changing

This copy is for your personal non-commercial use only

clicking herecolleagues clients or customers by you can order high-quality copies for yourIf you wish to distribute this article to others

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can be obtained byPermission to republish or repurpose articles or portions of articles

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including high-resolution figures can be found in the onlineUpdated information and services

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1259855-4 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 sciencemagorg SCIENCE

Table 1 The updated control variables and their current values along with the proposed boundaries and zones of uncertainty for all nine planetaryboundaries In the first column the name for the Earth-system process used in the original PB publication (R2009 reference 1) is given for comparison

Earth-systemprocess

Controlvariable(s)

Planetary boundary(zone of uncertainty)

Current value ofcontrol variable

Climatechange(R2009same)

Atmospheric CO2

concentration ppm

Energy imbalanceat top-of-atmosphere W mndash2

350 ppm CO2 (350ndash450 ppm)

+10 W mndash2 (+10ndash15 W mndash2)

3985 ppm CO2

23 W mndash2

(11ndash33 W mndash2)

Change inbiosphereintegrity(R2009Rate ofbiodiversityloss)

Genetic diversityExtinction rate

Functional diversityBiodiversityIntactness Index (BII)

Note These areinterim controlvariables until moreappropriate ones aredeveloped

lt 10 EMSY (10ndash100 EMSY)but with an aspirational goal ofca 1 EMSY (the backgroundrate of extinction loss) EMSY =extinctions per million species-years

Maintain BII at 90 (90ndash30)or above assessedgeographically by biomeslargeregional areas (eg southernAfrica) major marineecosystems (eg coral reefs) orby large functional groups

100ndash1000 EMSY

84 applied tosouthern Africaonly

Stratosphericozonedepletion(R2009 same)

Stratospheric O3

concentration DUlt5 reduction from pre-industrial level of 290 DU(5ndash10) assessed bylatitude

Only transgressedover Antarctica inAustral spring(~200 DU)

Oceanacidification(R2009same)

Carbonate ionconcentrationaverage globalsurface oceansaturation state withrespect to aragonite(Warag)

ge80 of the pre-industrialaragonite saturation state ofmean surface ocean includingnatural diel and seasonalvariability (ge80ndash ge70)

~84 of thepre-industrialaragonitesaturation state

Biogeochemicalflows (P andN cycles)(R2009Biogeochemicalflows (interferencewith P and Ncycles))

P Global P flowfrom freshwatersystems into theocean

P Regional P flowfrom fertilizers toerodible soils

N Global Industrialand intentionalbiological fixationof N

11 Tg P yrndash1 (11ndash100 Tg P yrndash1)

62 Tg yrndash1 mined and applied toerodible (agricultural) soils(62-112 Tg yrndash1) Boundary is aglobal average but regionaldistribution is critical forimpacts

62 Tg N yrndash1 (62ndash82 Tg N yrndash1)Boundary acts as a globallsquovalversquo limiting introduction ofnew reactive N to Earth Systembut regional distribution offertilizer N is critical forimpacts

~22 Tg P yrndash1

~14 Tg P yrndash1

~150 Tg N yrndash1

RESEARCH | RESEARCH ARTICLE

events inmany regions of the world is increasing(17) changes in atmospheric circulation patternshave increased drought in some regions of theworld (17) and the rate of combined mass lossfrom the Greenland and Antarctic ice sheets isincreasing (36)

Changes in biosphere integrity

We propose a two-component approach address-ing two key roles of the biosphere in the Earthsystem The first captures the role of geneticallyunique material as the ldquoinformation bankrdquo thatultimately determines the potential for life to

continue to coevolve with the abiotic componentof the Earth system in the most resilient waypossible Genetic diversity provides the long-termcapacity of the biosphere to persist under andadapt to abrupt and gradual abiotic change Thesecond captures the role of the biosphere inEarth-system functioning through the value rangedistribution and relative abundance of the func-tional traits of the organisms present in an eco-system or biota (7)For the first role the concept of phylogenetic

species variability (PSV) (7 33 37) would be anappropriate control variable However because

global data are not yet available for PSV we re-tain the global extinction rate as an interim con-trol variable although it is measured inaccuratelyand with a time lag There may be a considerablerisk in using extinction rate as a control variablebecause phylogenetic (and functional) diversitymay be more sensitive to human pressures thanspecies-level diversity (38) In principle the bound-ary should be set at a rate of loss of PSV no greaterthan the rate of evolution of new PSV during theHolocene Because that is unknown wemust fallback on the (imperfectly) known extinction rateof well-studied organisms over the past several

SCIENCE sciencemagorg 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 1259855-5

Earth-systemprocess

Controlvariable(s)

Planetary boundary(zone of uncertainty)

Current value ofcontrol variable

Land-systemchange(R2009same)

Global Area offorested land as of original forestcover

Biome Area offorested land as of potential forest

Global 75 (75ndash54) Valuesare a weighted average of thethree individual biomeboundaries and their uncertaintyzones

BiomeTropical 85 (85ndash60)Temperate 50 (50ndash30)Boreal 85 (85ndash60)

62

Freshwateruse(R2009Globalfreshwateruse)

Global Maximumamount ofconsumptive bluewater use (km3yrndash1)

Basin Blue waterwithdrawal as ofmean monthly riverflow

Global 4000 km3 yrndash1

(4000ndash6000 km3 yrndash1)

Basin Maximum monthlywithdrawal as a percentageof mean monthly river flowFor low-flow months 25(25ndash55) for intermediate-flow months 30 (30ndash60)for high-flow months 55(55ndash85)

~2600 km3 yrndash1

Atmosphericaerosolloading(R2009same)

Global AerosolOptical Depth(AOD) but muchregional variation

Regional AOD asa seasonal averageover a region SouthAsian Monsoonused as a case study

Regional (South AsianMonsoon as a case study)anthropogenic total (absorbingand scattering) AOD overIndian subcontinent of 025(025ndash050) absorbing(warming) AOD less than 10of total AOD

030 AOD overSouth Asianregion

Introductionof novel entities(R2009 Chemicalpollution)

No control variablecurrently defined

No boundary currentlyidentified but see boundaryfor stratospheric ozone for anexample of a boundaryrelated to a novel entity (CFCs)

RESEARCH | RESEARCH ARTICLE

million yearsmdashabout 1 per million species-years(39)mdashand add a large uncertainty bound raisingthe boundary to 10 permillion species-years Therisk is that although the Earth system can tol-erate a higher-than-background level of extinc-tions for a time we do not knowwhat levels of ortypes of biodiversity lossmay possibly trigger non-linear or irreversible changes to the Earth systemThe second control variable aims to capture the

role of the biosphere in Earth-system functioningand measures loss of biodiversity components atboth global and biomelarge ecosystem levels Al-though several variables have been developed atlocal scales for measuring functional diversity[eg (40)] finding an appropriate control varia-ble at regional or global levels is challenging Forthe present we propose an interim control var-iable the Biodiversity Intactness Index (BII) (41)BII assesses change in population abundance as aresult of human impacts such as land or resourceuse across a wide range of taxa and functionalgroups at a biome or ecosystem level using pre-industrial era abundance as a reference point Theindex typically ranges from 100 (abundancesacross all functional groups at preindustrial levels)to lower values that reflect the extent and degreeof human modification of populations of plantsand animals BII values for particular functionalgroups can go above 100 if humanmodificationsto ecosystems lead to increases in the abundanceof those speciesDue to a lack of evidence on the relationship

between BII and Earth-system responses we pro-

pose a preliminary boundary at 90 of the BIIbut with a very large uncertainty range (90 to30) that reflects the large gaps in our knowl-edge about the BIIndashEarth-system functioningrelationship (42 43) BII has been so far appliedto southern Africarsquos terrestrial biomes only (seefig S3 for an estimation of aggregated humanpressures on the terrestrial biosphere globally)where the index (not yet disaggregated to func-tional groups) was estimated to be 84 BIIranged from 69 to 91 for the seven countrieswhere it has been applied (41) Observations acrossthese countries suggest that decreases in BII ad-equately capture increasing levels of ecosystemdegradation defined as land uses that do not al-ter the land-cover type but lead to a persistentloss in ecosystem productivity (41)In addition to further work on functional mea-

sures such as BII in the longer term the conceptof biome integritymdashthe functioning and persist-ence of biomes at broad scales (7)mdashoffers a prom-ising approach and with further research couldprovide a set of operational control variables (oneper biome) that is appropriate robust and scien-tifically based

Stratospheric ozone depletion

We retain the original control variable [O3 con-centration in DU (Dobson units)] and boundary(275 DU) This boundary is only transgressedover Antarctica in the austral spring when O3

concentration drops to about 200 DU (44) How-ever the minimum O3 concentration has been

steady for about 15 years and is expected to riseover the coming decades as the ozone hole isrepaired after the phasing out of ozone-depletingsubstances This is an example in which after aboundary has been transgressed regionally hu-manity has taken effective action to return theprocess back to within the boundary

Ocean acidification

This boundary is intimately linked with one ofthe control variables CO2 for the climate changePB The concentration of free H+ ions in the sur-face ocean has increased by about 30 over thepast 200 years due to the increase in atmosphericCO2 (45) This in turn influences carbonate chem-istry in surface ocean waters Specifically it lowersthe saturation state of aragonite (Warag) a form ofcalcium carbonate formed by many marine orga-nisms At Warag lt 1 aragonite will dissolve Nonew evidence has emerged to suggest that theoriginally proposed boundary (ge80 of the pre-industrial average annual global Warag) shouldbe adjusted although geographical heterogeneityin Warag is important in monitoring the state ofthe boundary around the worldrsquos oceans (fig S4)Currently Warag is approximately equal to 84 ofthe preindustrial value (46) This boundary wouldnot be transgressed if the climate-change bound-ary of 350 ppm CO2 were to be respected

Biogeochemical flows

The original boundary was formulated for phos-phorus (P) and nitrogen (N) only but we nowpropose a more generic PB to encompass humaninfluence on biogeochemical flows in general Al-though the carbon cycle is covered in the climate-change boundary other elements such as silicon(47 48) are also important for Earth-system func-tioning Furthermore there is increasing evidencethat ratios between elements in the environmentmay have impacts on biodiversity on land and inthe sea (49ndash51) Thus we may ultimately need todevelop PBs for other elements and their ratiosalthough for now we focus on P and N onlyA two-level approach is now proposed for the

P component of the biogeochemical flows bound-ary (see also the supplementary materials) Theoriginal global-level boundary based on the pre-vention of a large-scale ocean anoxic event isretained with the proposed boundary set at asustained flow of 11 Tg P yearndash1 from freshwatersystems into the ocean Based on the analysis ofCarpenter and Bennett (3) we now propose anadditional regional-level P boundary designedto avert widespread eutrophication of freshwatersystems at a flow of 62 Tg P yearndash1 from fer-tilizers (mined P) to erodible soilsGiven that the addition of P to regional

watersheds is almost entirely from fertilizers theregional-level boundary applies primarily to theworldrsquos croplands The current global rate of ap-plication of P in fertilizers to croplands is 142 TgP yearndash1 (52 53) Observations point toward a fewagricultural regions of very high P applicationrates as the main contributors to the transgres-sion of this boundary (Fig 2 and fig S5A) andsuggest that a redistribution of P from areas

1259855-6 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 sciencemagorg SCIENCE

Fig 3The current status of the control variables for seven of the nine planetary boundaries Thegreen zone is the safe operating space (below the boundary) yellow represents the zone of uncertainty(increasing risk) and red is the high-risk zoneThe planetary boundary itself lies at the inner heavy circleThe control variables have been normalized for the zone of uncertainty (between the two heavy circles)the center of the figure therefore does not represent values of 0 for the control variables The controlvariable shown for climate change is atmospheric CO2 concentration Processes for which global-levelboundaries cannot yet be quantified are represented by gray wedges these are atmospheric aerosolloading novel entities and the functional role of biosphere integrity Modified from (1)

RESEARCH | RESEARCH ARTICLE

where it is currently in excess to areas where thesoil is naturally P-poormay simultaneously boostglobal crop production and reduce the transgres-sion of the regional-level P boundary (3 52 54)The N boundary has been taken from the com-

prehensive analysis of de Vries et al (5) whichproposed a PB for eutrophication of aquatic eco-systems of 62 Tg N yearndash1 from industrial andintentional biological N fixation using the moststringent water quality criterion As for the Pboundary a few agricultural regions of very highN application rates are the main contributors tothe transgression of this boundary (Fig 2 andfig S5B) This suggests that a redistribution of Ncould simultaneously boost global crop produc-tion and reduce the transgression of the regional-level boundaryBecause the major anthropogenic perturba-

tion of both the N and P cycles arises from fertil-izer application we can analyze the links betweenthe independently determined N and P bounda-ries in an integrated way based on the NP ratioin the growing plant tissue of agricultural cropsApplying this ratio which is on average 118 (55)to the P boundary (62 Tg P yearndash1) gives an Nboundary of 73 Tg N yearndash1 Conversely applyingthe ratio to theN boundary (62 TgN yearndash1) givesa P boundary of 53 Tg P yearndash1 The small dif-ferences between the boundaries derived usingthe NP ratio and those calculated independent-ly which are likely nonsignificant differencesgiven the precision of the data available for thecalculations show the internal consistency inour approach to the biogeochemical boundariesMore detail on the development of the P andN

boundaries is given in (33) where we also em-phasize that the proposed P and N boundariesmay be larger for an optimal allocation of N (andP) over the globe

Land-system change

The updated biosphere integrity boundary pro-vides a considerable constraint on the amountand pattern of land-system change in all ter-restrial biomes forests woodlands savannasgrasslands shrublands tundra and so on Theland-system change boundary is now focusedmore tightly on a specific constraint the biogeo-physical processes in land systems that directlyregulate climatemdashexchange of energy water andmomentum between the land surface and theatmosphere The control variable has been changedfrom the amount of cropland to the amount offorest cover remaining as the three major forestbiomesmdashtropical temperate and borealmdashplay astronger role in land surfacendashclimate couplingthan other biomes (56 57) In particular we fo-cus on those land-system changes that can in-fluence the climate in regions beyond the regionwhere the land-system change occurredOf the forest biomes tropical forests have sub-

stantial feedbacks to climate through changes inevapotranspiration when they are converted tononforested systems and changes in the distribu-tion of boreal forests affect the albedo of the landsurface and hence regional energy exchange Bothhave strong regional and global teleconnections

The biome-level boundary for these two types offorest have been set at 85 (Table 1 and thesupplementary materials) and the boundary fortemperate forests has been proposed at 50 ofpotential forest cover because changes to tem-perate forests are estimated to have weaker in-fluences on the climate system at the global levelthan changes to the other two major forestbiomes (56) These boundaries would almostsurely be met if the proposed biosphere integ-rity boundary of 90 BII were respectedEstimates of the current status of the land-

system change boundary are given in Figs 2 and3 and fig S6 and in (58)

Freshwater use

The revised freshwater use boundary has retainedconsumptive use of blue water [from rivers lakesreservoirs and renewable groundwater stores(59)] as the global-level control variable and4000 km3year as the value of the boundaryThis PB may be somewhat higher or lower de-pending on riversrsquo ecological flow requirements(6) Therefore we report here a new assessmentto complement the PB with a basin-scale bound-ary for the maximum rate of blue water with-drawal along rivers based on the amount of waterrequired in the river system to avoid regime shiftsin the functioning of flow-dependent ecosystemsWe base our control variable on the concept ofenvironmental water flows (EWF) which definesthe level of river flows for different hydrologicalcharacteristics of river basins adequate to main-tain a fair-to-good ecosystem state (60ndash62)The variable monthly flow (VMF) method

(33 63) was used to calculate the basin-scaleboundary for water This method takes accountof intra-annual variability by classifying flow re-gimes into high- intermediate- and low-flowmonths and allocating EWF as a percentage ofthe mean monthly flow (MMF) Based on thisanalysis the zones of uncertainty for the river-basin scale water boundary were set at 25 to 55of MMF for the low-flow regime 40 to 70 forthe intermediate-flow regime and 55 to 85 forthe high-flow regime (table S2) The boundarieswere set at the lower end of the uncertaintyranges that encompass average monthly EWFOur new estimates of the current status of thewater use boundarymdashcomputed based on gridcellndashspecific estimates of agricultural industrialand domestic water withdrawalsmdashare shown inFigs 2 and 3 with details in figs S7 and S8

Atmospheric aerosol loading

Aerosols have well-known serious human healtheffects leading to about 72 million deaths peryear (64) They also affect the functioning of theEarth system in many ways (65) (fig S9) Herewe focus on the effect of aerosols on regionalocean-atmosphere circulation as the rationalefor a separate aerosols boundary We adopt aero-sol optical depth (AOD) (33) as the control var-iable and use the south Asian monsoon as a casestudy based on the potential of widespread aero-sol loading over the Indian subcontinent to switchthe monsoon system to a drier state

The background AOD over south Asia is ~015and can be as high as 04 during volcanic events(66) Emissions of black carbon and organic car-bon from cooking and heating with biofuels andfrom diesel transportation and emission of sul-fates and nitrates from fossil fuel combustioncan increase seasonal mean AODs to as high as04 (larger during volcanic periods) leading todecreases of 10 to 15 of incident solar radiationat the surface (fig S9) A substantial decrease inmonsoon activity is likely around an AOD of 050an increase of 035 above the background (67)Taking a precautionary approach toward uncer-tainties surrounding the position of the tippingpoint we propose a boundary at an AOD of 025(an increase due to human activities of 01) witha zone of uncertainty of 025 to 050 The annualmean AOD is currently about 03 (66) within thezone of uncertainty

Introduction of novel entities

We define novel entities as new substances newforms of existing substances and modified lifeforms that have the potential for unwanted geo-physical andor biological effects Anthropogenicintroduction of novel entities to the environmentis of concern at the global level when these en-tities exhibit (i) persistence (ii) mobility acrossscales with consequent widespread distributionsand (iii) potential impacts on vital Earth-systemprocesses or subsystems These potentially in-clude chemicals and other new types of engi-neered materials or organisms [eg (68ndash71)] notpreviously known to the Earth system as well asnaturally occurring elements (for example heavymetals) mobilized by anthropogenic activitiesThe risks associated with the introduction ofnovel entities into the Earth system are exempli-fied by the release of CFCs (chlorofluorocarbons)which are very useful synthetic chemicals thatwere thought to be harmless but had unexpecteddramatic impacts on the stratospheric ozone layerIn effect humanity is repeatedly running suchglobal-scale experiments but not yet applying theinsights from previous experience to new appli-cations (72 73)Today there aremore than 100000 substances

in global commerce (74) If nanomaterials andplastic polymers that degrade to microplasticsare included the list is even longer There is alsoa ldquochemical intensificationrdquo due to the rapidlyincreasing global production of chemicals theexpanding worldwide distribution as chemicalproducts or in consumer goods and the exten-sive global trade in chemical wastes (75)In recent years there has been a growing de-

bate about the global-scale effects of chemicalpollution leading to calls for the definition ofcriteria to identify the kinds of chemical sub-stances that are likely to be globally problematic(76 77) Persson et al (73) proposed that there arethree conditions that need to be fulfilled for achemical to pose a threat to the Earth system (i)the chemical has an unknown disruptive effecton a vital Earth-systemprocess (ii) the disruptiveeffect is not discovered until it is a problem at theglobal scale and (iii) the effect is not readily

SCIENCE sciencemagorg 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 1259855-7

RESEARCH | RESEARCH ARTICLE

reversible The challenge to the research commu-nity is to develop the knowledge base that allowsthe screening of chemicals before they are re-leased into the environment for properties thatmay predispose them toward becoming globalproblemsAs a first step toward meeting this challenge

the three conditions outlined above have beenused as the basis for identifying scenarios ofchemical pollution that fulfill the conditions andas a next step for pinpointing chemical profilesthat fit the scenarios (28) This proposal consti-tutes a first attempt at adding the Earth-systemperspective when assessing hazard and risk ofchemicals and offers a vision for a systematic ap-proach to a complex management situation withmany unknownsDespite this progress in developing an Earth-

systemndashoriented approach there is not yet anaggregate global-level analysis of chemical pol-lution on which to base a control variable or aboundary value It may also serve little purposeto define boundary values and control varia-bles for a planetary boundary of this complexityNevertheless there is a potential threat fromnovel entities to disrupt the functioning of theEarth-system and society needs to learn how tomitigate these unknown risks and manage chem-icals under uncertainty (28 73)Some precautionary and preventive actions

can be considered These may include a strongerfocus on green chemistry (78) finding synergieswith risk-reducing interventions in other fieldssuch as occupational health (79) paying moreattention to learning from earlier mistakes (8081) and investing in science to better under-stand and monitor vital Earth-system processesin order to be able to detect disruptive effectsfrom novel entities as early as possible

Hierarchy of boundaries

An analysis of the many interactions among theboundaries (table S3 and fig S10) suggests thattwo of themmdashclimate change and biosphereintegritymdashare highly integrated emergent system-level phenomena that are connected to all of theother PBs They operate at the level of the wholeEarth system (7) and have coevolved for nearly4 billion years (82) They are regulated by theother boundaries and on the other hand pro-vide the planetary-level overarching systems with-in which the other boundary processes operateFurthermore large changes in the climate or inbiosphere integrity would likely on their ownpush the Earth system out of the Holocene stateIn fact transitions between time periods in Earthhistory have often been delineated by substantialshifts in climate the biosphere or both (82 83)These observations suggest a two-level hierar-

chy of boundaries in which climate change andbiosphere integrity should be recognized as coreplanetary boundaries through which the otherboundaries operate The crossing of one or moreof the other boundaries may seriously affect hu-man well-being and may predispose the trans-gression of a core boundary(ies) but does not byitself lead to a new state of the Earth system This

hierarchical approach to classifying the bounda-ries becomes clearer by examining inmore detailthe roles of climate and biosphere integrity in thefunctioning of the Earth systemThe climate system is a manifestation of the

amount distribution and net balance of energyat Earthrsquos surface The total amount of energysets the overall conditions for life In Earthrsquos cur-rent climate a range of global surface temper-atures and atmospheric pressures allows the threephases of water to be present simultaneouslywith ice and water vapor playing critical roles inthe physical feedbacks of the climate system Thedistribution of energy by latitude over the landand sea surfaces and within the ocean plays amajor role in the circulation of the two greatfluids the ocean and the atmosphere These sys-temic physical characteristics are key spatial de-terminants of the distribution of the biota andthe structure and functioning of ecosystems andare controllers of biogeochemical flowsBiosphere integrity is also crucial to Earth-

system functioning where the biosphere is de-fined as the totality of all ecosystems (terrestrialfreshwater andmarine) on Earth and their biota(32) These ecosystems and biota play a criticalrole in determining the state of the Earth systemregulating its material and energy flows and itsresponses to abrupt and gradual change (7) Di-versity in the biosphere provides resilience toterrestrial and marine ecosystems (83 84) Thebiosphere not only interacts with the other plan-etary boundaries but also increases the capacityof theEarth system topersist in a given state underchanges in these other boundaries The ultimatebasis for the many roles that the biosphere playsin Earth-system dynamics is the genetic code ofthe biota the basic information bank that de-fines the biospherersquos functional role and its ca-pacity to innovate and persist into the future

Planetary boundaries in asocietal context

A proposed approach for sustainable develop-ment goals (SDGs) (85) argues that the stablefunctioning of the Earth system is a prereq-uisite for thriving societies around the world Thisapproach implies that the PB framework orsomething like it will need to be implementedalongside the achievement of targets aimed atmore immediate human needs such as provi-sion of clean affordable and accessible energyand the adequate supply of food World devel-opment within the biophysical limits of a stableEarth system has always been a necessity [eg(86 87)] However only recently for a numberof reasons has it become possible to identifyevaluate and quantify risks of abrupt planetary-and biome-level shifts due to overshoot of keyEarth-system parameters (i) the emergence ofglobal-change thinking and Earth-system think-ing (88) (ii) the rise of ldquothe Planetaryrdquo as a rel-evant level of complex system understanding(89ndash92) and (iii) observable effects of the rapidincrease in human pressures on the planet (16)The PB approach is embedded in this emerg-

ing social context but it does not suggest how to

maneuver within the safe operating space in thequest for global sustainability For example thePB framework does not as yet account for the re-gional distribution of the impact or its histor-ical patterns Nor does the PB framework takeinto account the deeper issues of equity and cau-sation The current levels of the boundary pro-cesses and the transgressions of boundaries thathave already occurred are unevenly caused bydifferent human societies and different socialgroups The wealth benefits that these trans-gressions have brought are also unevenly distrib-uted socially and geographically It is easy toforesee that uneven distribution of causation andbenefits will continue and these differentialsmust surely be addressed for a Holocene-likeEarth-system state to be successfully legitimatedand maintained However the PB framework ascurrently construed provides no guidance as tohow this may be achieved [although some po-tential synergies have been noted (54)] and itcannot readily be used tomake choices betweenpathways for piecemeal maneuvering withinthe safe operating space ormore radical shifts ofglobal governance (93)The nature of the PB framework implies that

two important cautions should be observedwhenapplication of the framework to policy or man-agement is proposed boundary interactions andscale

Boundary interactions

The planetary boundaries framework arises fromthe scientific evidence that Earth is a singlecomplex integrated systemmdashthat is the bound-aries operate as an interdependent set [eg(94)] (table S1 and fig S10) Although a system-atic quantitative analysis of interactions amongall of the processes for which boundaries areproposed remains beyond the scope of currentmodeling and observational capacity the Earthsystem clearly operates in well-defined states inwhich these processes and their interactionscan create stabilizing or destabilizing feedbacks(16 90 95) This has profound implications forglobal sustainability because it emphasizes theneed to address multiple interacting environ-mental processes simultaneously (eg stabilizingthe climate system requires sustainable forestmanagement and stable ocean ecosystems)

Scale

The PB framework is not designed to be ldquodown-scaledrdquo or ldquodisaggregatedrdquo to smaller levels suchas nations or local communities That said thePB framework recognizes the importance ofchanges at the level of subsystems in the Earthsystem (eg biomes or large river basins) on thefunctioning of the Earth system as a whole Alsothere are strong arguments for an integrated ap-proach coupling boundary definitions at region-al and global levels with development goals toenable the application of ldquoPB thinkingrdquo at lev-els (nations basins and regions) where policyaction most commonly occurs [eg (85 96)]This update of the PB framework is one step on

a longer-term evolution of scientific knowledge to

1259855-8 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 sciencemagorg SCIENCE

RESEARCH | RESEARCH ARTICLE

inform and support global sustainability goalsand pathways This evolution is needed morethan ever before there are severe implementa-tion gaps inmany global environmental policiesrelating to the PB issues where problematictrends are not being halted or reversed despiteinternational consensus about the urgency of theproblems The prospect of tighter resource con-straints and rising environmental hazards is alsounavoidably turning the focus onto global socialequity and the planetary stewardship of Earthrsquoslife-support system There is a need for a trulyglobal evidence base with much greater integra-tion among issues in order to respond to theseglobal challenges New research initiatives [egFuture Earth (wwwfutureearthorg)] provide evi-dence that science can respond to this need byapplying Earth-system research to advance a newgeneration of integrated global analyses and toexplore options for transformations toward sus-tainability This is a clear sign that as the risksof the Anthropocene to human well-being be-come clearer research is maturing to a pointwhere a systemic step-change is possiblemdashandnecessarymdashin exploring and defining a safe andjust planetary operating space for the furtherdevelopment of human societies

Methods summary

Our approach to building the planetary bound-aries framework is described above We haveimplemented the framework through an ex-pert assessment and synthesis of the scientificknowledge of intrinsic biophysical processes thatregulate the stability of the Earth system Ourprecautionary approach is based on the main-tenance of a Holocene-like state of the Earthsystem and on an assessment of the level ofhuman-driven change that would risk destabi-lizing this state For the climate change PB thereis already much literature on which to basesuch an assessment For others such as strato-spheric ozone ocean acidification extinctionrates and P andN cycles we have used estimatesof preindustrial values of the control variableas a Holocene baseline Where large undesira-ble thresholds exist and have been studied (egpolar ice sheets Amazon rainforest aragonitedissolution atmospheric aerosols and the southAsian monsoon) quantitative boundaries can bereadily proposed For others where the focus ison erosion of Earth-system resilience the bound-aries are more difficult (but not impossible) toquantify as reflected in larger uncertainty zonesWe used large-scale assessments of the impacts

of human activities on Earth-system functioning[eg Intergovernmental Panel on Climate Change(17 18) the International Geosphere-BiosphereProgramme synthesis (16) and chemicals (75 80)]as sources of community-level understandingon which to propose PBs Our update has alsorelied on post-2009 assessments of individualboundaries by the relevant expert research com-munities examples include phosphorus (3) ni-trogen (5) biosphere integrity (7) freshwater use(5 63) and novel entities [with a focus on chem-icals (28 73)] Finally some new analyses have

been undertaken specifically for this paper (i) afreshwater-use PB based on the EWF approach(33 63) (ii) the linkage of the phosphorus andnitrogen boundaries via the NP ratio in grow-ing crop tissue (33) and (iii) the use of majorforest biomes as the basis for the land-systemchange PB (33)

REFERENCES AND NOTES

1 J Rockstroumlm et al Planetary boundaries Exploring the safeoperating space for humanity Ecol Soc 14 32 (2009)httpwwwecologyandsocietyorgvol14iss2art32

2 J Rockstroumlm et al A safe operating space for humanityNature 461 472ndash475 (2009) doi 101038461472apmid 19779433

3 S R Carpenter E M Bennett Reconsideration of theplanetary boundary for phosphorus Environ Res Lett 6014009 (2011) doi 1010881748-932661014009

4 S W Running Ecology A measurable planetary boundaryfor the biosphere Science 337 1458ndash1459 (2012)doi 101126science1227620 pmid 22997311

5 W de Vries J Kros C Kroeze S P Seitzinger Assessingplanetary and regional nitrogen boundaries related to foodsecurity and adverse environmental impacts Curr OpinionEnviron Sust 5 392ndash402 (2013) doi 101016jcosust201307004

6 D Gerten et al Towards a revised planetary boundary forconsumptive freshwater use Role of environmental flowrequirements Curr Opinion Environ Sust 5 551ndash558 (2013)doi 101016jcosust201311001

7 G M Mace et al Approaches to defining a planetary boundaryfor biodiversity Glob Environ Change 28 289ndash297 (2014)doi 101016jgloenvcha201407009

8 V Galaz Global Environmental Governance Technology andPolitics The Anthropocene Gap (Edward Elgar CheltenhamUK 2014)

9 UN GSP (UN High-Level Panel on Global Sustainability)Resilient People Resilient Planet A Future Worth Choosing(Report for the 2012 Rio+20 Earth Summit United NationsNew York 2012)

10 WBCSD (World Business Council on Sustainable Development)Action 2020 Overview (WBCSD Geneva Switzerlandhttpaction2020org accessed 18 June 2014)

11 R Costanza L Graumlich W Steffen Eds Integrated Historyand Future of People on Earth (MIT Press CambridgeMA USA 2006)

12 S Soumlrlin P Warde in Naturersquos End History and theEnvironment S Soumlrlin P Warde Eds (Palgrave MacMillanLondon 2009) pp 1ndash19

13 R C Bishop Endangered species and uncertainty Theeconomics of a safe minimum standard Am J Agric Econ 6110ndash18 (1978) doi 1023071240156

14 T M Crowards Safe minimum standards Costs andopportunities Ecol Econ 25 303ndash314 (1998) doi 101016S0921-8009(97)00041-4

15 W Steffen J Crutzen J R McNeill The Anthropocene Arehumans now overwhelming the great forces of NatureAmbio 36 614ndash621 (2007) doi 1015790044-7447(2007)36[614TAAHNO]20CO2 pmid 18240674

16 W Steffen et al Global Change and the Earth System A PlanetUnder Pressure (The IGBP Book Series Springer-VerlagBerlin Heidelberg New York 2004)

17 IPCC (Intergovernmental Panel on Climate Change) Managingthe risks of extreme events and disasters to advanceclimate change adaptation A special report of Working GroupsI and II of the IPCC CB Field et al Eds (CambridgeUniversity Press Cambridge UK (2012) doi 101017CBO9781139177245

18 IPCC (Intergovernmental Panel on Climate Change) ClimateChange 2013 The Physical Science Basis Summary forPolicymakers L Alexander et al Eds (IPCC SecretariatGeneva Switzerland 2013) doi 101017CBO9781107415324

19 P J Crutzen Geology of mankind Nature 415 23 (2002)doi 101038415023a pmid 11780095

20 K Richardson W Steffen D Liverman Climate Change GlobalRisks Challenges and Decisions (Cambridge Univ PressCambridge UK 2011)

21 T M Lenton et al Tipping elements in the Earthrsquos climatesystem Proc Natl Acad Sci USA 105 1786ndash1793 (2008)doi 101073pnas0705414105 pmid 18258748

22 M Scheffer et al Early-warning signals for criticaltransitions Nature 461 53ndash59 (2009) doi 101038nature08227 pmid 19727193

23 S R Carpenter W A Brock Rising variance A leadingindicator of ecological transition Ecol Lett 9 311ndash318 (2006)doi 101111j1461-0248200500877x pmid 16958897

24 J Bakke et al Rapid oceanic and atmospheric changes duringthe Younger Dryas cold period Nat Geosci 2 202ndash205(2009) doi 101038ngeo439

25 M Scheffer et al Anticipating critical transitions Science338 344ndash348 (2012) doi 101126science1225244pmid 23087241

26 R Wang et al Flickering gives early warning signals of acritical transition to a eutrophic lake state Nature 492419ndash422 (2012) doi 101038nature11655 pmid 23160492

27 R Biggs S R Carpenter W A Brock Turning back fromthe brink Detecting an impending regime shift in time to avertit Proc Natl Acad Sci USA 106 826ndash831 (2009)doi 101073pnas0811729106 pmid 19124774

28 M MacLeod et al Identifying chemicals that are planetaryboundary threats Environ Sci Technol 48 11057ndash11063(2014) doi 101021es501893m pmid 25181298

29 C S Holling Resilience and stability of ecological systemsAnnu Rev Ecol Syst 4 1ndash23 (1973) doi 101146annureves04110173000245

30 C Folke et al Resilience thinking Integrating resilienceadaptability and transformability Ecol Soc 15 20 (2010)wwwecologyandsocietyorgvol15iss4art20

31 T P Hughes S Carpenter J Rockstroumlm M SchefferB Walker Multiscale regime shifts and planetary boundariesTrends Ecol Evol 28 389ndash395 (2013) doi 101016jtree201305019 pmid 23769417

32 T M Lenton H T P Williams On the origin of planetary-scaletipping points Trends Ecol Evol 28 380ndash382 (2013)doi 101016jtree201306001 pmid 23777818

33 Supplementary text figures and tables are available onScience Online

34 NOAA (National Oceanic and Atmospheric Administration)NOAA-ESRL Annual CO2 Data accessed at httpco2noworgCurrent-CO2CO2-Nowannual-co2html (2014)

35 S E Perkins L V Alexander J Nairn Increasing frequencyintensity and duration of observed global heat waves and warmspells Geophys Res Lett 39 L20714 (2012) doi 1010292012GL053361

36 A Shepherd et al A reconciled estimate of ice-sheet massbalance Science 338 1183ndash1189 (2012) doi 101126science1228102 pmid 23197528

37 M R Helmus T J Bland C K Williams A R IvesPhylogenetic measures of biodiversity Am Nat 169 E68ndashE83(2007) doi 101086511334 pmid 17230400

38 S Drsquoagata et al Human-mediated loss of phylogeneticand functional diversity in coral reef fishes Curr Biol24 555ndash560 (2014) doi 101016jcub201401049pmid 24560574

39 A D Barnosky et al Has the Earthrsquos sixth mass extinctionalready arrived Nature 471 51ndash57 (2011) doi 101038nature09678 pmid 21368823

40 N W Mason F de Bello D Mouillot S Pavoine S Dray Aguide for using functional diversity indices to reveal changesin assembly processes along ecological gradients J VegSci 24 794ndash806 (2013) doi 101111jvs12013

41 R J Scholes R Biggs A biodiversity intactness index Nature434 45ndash49 (2005) doi 101038nature03289pmid 15744293

42 B Cardinale Ecology Impacts of biodiversity loss Science336 552ndash553 (2012) doi 101126science1222102pmid 22556243

43 D U Hooper et al A global synthesis reveals biodiversityloss as a major driver of ecosystem change Nature 486105ndash108 (2012) doi 101038nature11118pmid 22678289

44 BAS (British Antarctic Survey) ldquoAntarctic ozonerdquo wwwantarcticaacukmetjdsozoneindexhtmldata J ShanklinBritish Antarctic Survey (2013)

45 Royal Society Ocean Acidification Due to IncreasingAtmospheric Carbon Dioxide Policy Document 1205 (TheRoyal Society London 2005)

46 J M Guinotte V J Fabry Ocean acidification and its potentialeffects on marine ecosystems Ann N Y Acad Sci 1134320ndash342 (2008) doi 101196annals1439013pmid 18566099

47 D J Conley Terrestrial ecosystems and the globalbiogeochemical silica cycle Global Biogeochem Cycles 16681ndash688 (2002) doi 1010292002GB001894

SCIENCE sciencemagorg 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 1259855-9

RESEARCH | RESEARCH ARTICLE

48 F Vandevenne E Struyf W Clymans P Meire Agriculturalsilica harvest Have humans created a new loop in the globalsilica cycle Front Ecol Environ 10 243ndash248 (2012)doi 101890110046

49 S E Gress T D Nichols C C Northcraft W T PeterjohnNutrient limitation in soils exhibiting differing nitrogenavailabilities What lies beyond nitrogen saturation Ecol 88119ndash130 (2007) doi 1018900012-9658(2007)88[119NLISED]20CO2 pmid 17489460

50 H Hillebrand V Lehmpfuhl Resource stoichiometry andconsumers control the biodiversity-productivity relationship inpelagic metacommunities Am Nat 178 171ndash181 (2011)doi 101086660831 pmid 21750381

51 C M Moore et al Processes and patterns of oceanic nutrientlimitation Nat Geosci 6 701ndash710 (2013) doi 101038ngeo1765

52 G K MacDonald E M Bennett P A Potter N RamankuttyAgronomic phosphorus imbalances across the worldrsquoscroplands Proc Natl Acad Sci USA 108 3086ndash3091 (2011)doi 101073pnas1010808108 pmid 21282605

53 L Bouwman et al Exploring global changes in nitrogen andphosphorus cycles in agriculture induced by livestockproduction over the 1900-2050 period Proc Natl AcadSci USA 110 20882ndash20887 (2013) doi 101073pnas1012878108 pmid 21576477

54 W Steffen M Stafford Smith Planetary boundaries equityand global sustainability Why wealthy countries could benefitfrom more equity Curr Opinion Environ Sust 5 403ndash408(2013) doi 101016jcosust201304007

55 D J Greenwood et al A unifying concept for the dependenceof whole-crop N P ratio on biomass theory and experimentAnn Bot (Lond) 102 967ndash977 (2008) doi 101093aobmcn188 pmid 18840873

56 P K Snyder C Delire J A Foley Evaluating the influence ofdifferent vegetation biomes on the global climate Clim Dyn23 279ndash302 (2004) doi 101007s00382-004-0430-0

57 P C West G T Narisma C C Barford C J KucharikJ A Foley An alternative approach for quantifying climateregulation by ecosystems Front Ecol Environ 9 126ndash133(2010) doi 101890090015

58 EPI (Earth Policy Institute) ldquoForest coverrdquo wwwearthpolicyorgindicatorsC56forests_2012_ (2014)

59 M Falkenmark Meeting water requirements of an expandingworld population Philos Trans R Soc Lond B Biol Sci 352929ndash936 (1997) doi 101098rstb19970072

60 J S Wallace M C Acreman C A Sullivan The sharing ofwater between society and ecosystems From conflict tocatchment-based co-management Philos Trans R Soc LondB Biol Sci 358 2011ndash2026 (2003) doi 101098rstb20031383 pmid 14728795

61 N L Poff et al The natural flow regime A paradigm for riverconservation and restoration BioSci 47 769ndash784 (1997)doi 1023071313099

62 N L Poff J K H Zimmerman Ecological responses to alteredflow regimes A literature review to inform the science andmanagement of environmental flows Biol 55 194ndash205 (2010)doi 101111j1365-2427200902272x

63 A V Pastor F Ludwig H Biemans H Hoff P KabatAccounting for environmental flow requirements in globalwater assessments Hydrol Earth Syst Sci 18 5041ndash5059(2014) doi 105194hess-18-5041-2014

64 WHO (World Health Organization) Burden of Disease from theJoint Effects of Household and Ambient Air Pollution for 2012(wwwwhointphehealth_topicsoutdoorairdatabasesFINAL_HAP_AAP_BoD24March2014pdf accessed 23 June 2014httpwwwwhointphehealth_topicsoutdoorairdatabasesen)

65 O Boucher et al in Climate Change 2013 The Physical ScienceBasis IPCC AR5 WGI report T Stocker et al Eds (CambridgeUniv Press Cambridge UK 2013) chap 7 pp 571ndash657

66 M Chin et al Multi-decadal aerosol variations from 1980 to2009 A perspective from observations and a global modelAtmos Chem Phys 14 3657ndash3690 (2014) doi 105194acp-14-3657-2014

67 V Ramanathan et al Atmospheric brown clouds Impacts onSouth Asian climate and hydrological cycle Proc Natl AcadSci USA 102 5326ndash5333 (2005) doi 101073pnas0500656102 pmid 15749818

68 M Cole P Lindeque C Halsband T S Galloway Microplasticsas contaminants in the marine environment A review MarPollut Bull 62 2588ndash2597 (2011) doi 101016jmarpolbul201109025 pmid 22001295

69 EEA (European Environment Agency) Genetically ModifiedOrganisms (GMOs) The Significance of Gene Flow ThroughPollen Transfer (Environmental Issue Report 28 EuropeanEnvironment Agency Copenhagen Denmark 2002)

70 J A Ivar do Sul M F Costa The present and future ofmicroplastic pollution in the marine environment Environ Pollut185 352ndash364 (2014) doi 101016jenvpol201310036pmid 24275078

71 R Kessler Engineered nanoparticles in consumer productsUnderstanding a new ingredient Environ Health Perspect 119a120ndasha125 (2011) doi 101289ehp119-a120 pmid 21356630

72 M Rees Our Final Century Will Civilisation Survive theTwenty-first Century (Arrow Books London 2003)

73 L M Persson et al Confronting unknown planetary boundarythreats from chemical pollution Environ Sci Technol 4712619ndash12622 (2013) doi 101021es402501c pmid 23980998

74 P P Egeghy et al The exposure data landscape formanufactured chemicals Sci Total Environ 414 159ndash166(2012) doi 101016jscitotenv201110046 pmid 22104386

75 UNEP (United Nations Environment Programme) GCOGlobal Chemicals Outlook Towards Sound Management ofChemicals (United Nations Environment ProgrammeNairobi Kenya 2013)

76 S Strempel M Scheringer C A Ng K HungerbuumlhlerScreening for PBT chemicals among the ldquoexistingrdquo andldquonewrdquo chemicals of the EU Environ Sci Technol 465680ndash5687 (2012) doi 101021es3002713pmid 22494215

77 M Scheringer et al How many persistent organic pollutantsshould we expect Atmos Poll Res 3 383ndash391 (2012)doi 105094APR2012044

78 K Sanderson Chemistry Itrsquos not easy being green Nature469 18ndash20 (2011) doi 101038469018a pmid 21209638

79 P A Schulte et al Occupational safety and health greenchemistry and sustainability A review of areas ofconvergence Environ Health 12 31 (2013) doi 1011861476-069X-12-31 pmid 23587312

80 EEA (European Environment Agency) Late Lessons from EarlyWarnings The Precautionary Principle 1896-2000 (EnvironmentalIssue Report 222001 Copenhagen Denmark 2001)

81 D Gee Late lessons from early warnings Toward realism andprecaution with endocrine-disrupting substances EnvironHealth Perspect 114 (suppl 1) 152ndash160 (2006) doi 101289ehp8134 pmid 16818262

82 T Lenton A Watson A Revolutions That Made the Earth(Oxford Univ Press Oxford UK 2011)

83 R Biggs et al Toward principles for enhancing the resilienceof ecosystem services Annu Rev Environ Resour 37421ndash448 (2012) doi 101146annurev-environ-051211-123836

84 G S Cumming P Olsson F S Chapin III C S HollingResilience experimentation and scale mismatches in social-ecological systems Landscape Ecol 28 1139ndash1150 (2013)doi 101007s10980-012-9725-4

85 D Griggs et al Policy Sustainable development goals forpeople and planet Nature 495 305ndash307 (2013) doi 101038495305a pmid 23518546

86 R Costanza Ed Ecological Economics The Science andManagement of Sustainability (Columbia Univ PressNew York 1991)

87 C Folke in Linking the Natural Environment and the EconomyEssays from the Eco-Eco Group C Folke T Karingberger Eds(Kluwer Academic Publishers Dordrecht Netherlands 1991)pp 77ndash94

88 L Robin S Soumlrlin P Warde Eds The Future of NatureDocuments of Global Change (Yale Univ Press New Haven CT2013)

89 U Heise Sense of Place and Sense of Planet TheEnvironmental Imagination of the Global (Oxford Univ PressOxford 2008)

90 M Scheffer Critical Transitions in Nature and Society(Princeton Univ Press Princeton NJ 2009)

91 J Masco Bad weather On planetary crisis Soc Stud Sci 407ndash40 (2010) doi 1011770306312709341598

92 G Paacutelsson et al Reconceptualizing the lsquoAnthroposrsquo in theAnthropocene Integrating the social sciences and humanitiesin global environmental change research Environ Sci Policy28 4 (2013) doi 101016jenvsci201211004

93 N Castree et al Changing the intellectual climate NatureClim Change 4 763ndash768 (2014) doi 101038nclimate2339

94 J M Anderies S R Carpenter W Steffen J Rockstroumlm Thetopology of non-linear global carbon dynamics From tippingpoints to planetary boundaries Environ Res Lett 8 044048(2013) doi 1010881748-932684044048

95 S E Cornell I C Prentice J I House C J DownyUnderstanding the Earth System Global Change Science forApplication (Cambridge Univ Press Cambridge 2012)

96 J A Dearing et al Safe and just operating spaces for regionalsocial-ecological systems Glob Environ Change 28 227ndash238(2014) doi 101016jgloenvcha201406012

ACKNOWLEDGMENTS

We thank J Foley and N Ramunkutty for contributions to theland-system change boundary A Pastor for analytical work on thePB for freshwater B Armstrong C Butler T McMichael andA Woodward for contributions to the novel entities boundary andB Scholes for comments on an earlier version of the manuscriptData associated with the paper are located at the StockholmResilience Centre Sweden (httpwwwstockholmresilienceorg21researchresearch-programmesplanetary-boundarieshtml)The planetary boundaries research at the Stockholm ResilienceCentre is made possible through a core grant from MISTRA(Swedish Foundation for Strategic Environmental Research) SECis supported by the Swedish Research Council EMB is supportedby the Natural Sciences and Engineering Research Council ofCanada and by the Trottier Institute for Science and Public PolicyRB is supported by a Branco Weiss Fellowship CF is supportedby the Family Erling Persson Academy Programme on GlobalEconomic Dynamics and the Biosphere IF is supported by theStordalen Foundation (Norway) SS is supported by theRiksbanken Jubileumsfond and the Institute for Advanced StudyPrinceton NJ and SRC and VR are supported bythe US National Science Foundation

SUPPLEMENTARY MATERIALS

wwwsciencemagorgcontent34762231259855supplDC1MethodsFigs S1 to S10Tables S1 to S3References (97ndash158)

11 August 2014 accepted 8 January 2015Published online 15 January 2015101126science1259855

1259855-10 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 sciencemagorg SCIENCE

RESEARCH | RESEARCH ARTICLE

DOI 101126science1259855 (2015)347 Science

et alWill SteffenplanetPlanetary boundaries Guiding human development on a changing

This copy is for your personal non-commercial use only

clicking herecolleagues clients or customers by you can order high-quality copies for yourIf you wish to distribute this article to others

herefollowing the guidelines

can be obtained byPermission to republish or repurpose articles or portions of articles

) February 12 2015 wwwsciencemagorg (this information is current as of

The following resources related to this article are available online at

httpwwwsciencemagorgcontent34762231259855fullhtmlversion of this article at

including high-resolution figures can be found in the onlineUpdated information and services

httpwwwsciencemagorgcontentsuppl20150114science1259855DC1html can be found at Supporting Online Material

httpwwwsciencemagorgcontent34762231259855fullhtmlrelatedfound at

can berelated to this article A list of selected additional articles on the Science Web sites

httpwwwsciencemagorgcontent34762231259855fullhtmlref-list-1 27 of which can be accessed freecites 120 articlesThis article

httpwwwsciencemagorgcgicollectionecologyEcology

subject collectionsThis article appears in the following

registered trademark of AAAS is aScience2015 by the American Association for the Advancement of Science all rights reserved The title

CopyrightAmerican Association for the Advancement of Science 1200 New York Avenue NW Washington DC 20005 (print ISSN 0036-8075 online ISSN 1095-9203) is published weekly except the last week in December by theScience

on

Feb

ruar

y 13

201

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ence

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org

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from

events inmany regions of the world is increasing(17) changes in atmospheric circulation patternshave increased drought in some regions of theworld (17) and the rate of combined mass lossfrom the Greenland and Antarctic ice sheets isincreasing (36)

Changes in biosphere integrity

We propose a two-component approach address-ing two key roles of the biosphere in the Earthsystem The first captures the role of geneticallyunique material as the ldquoinformation bankrdquo thatultimately determines the potential for life to

continue to coevolve with the abiotic componentof the Earth system in the most resilient waypossible Genetic diversity provides the long-termcapacity of the biosphere to persist under andadapt to abrupt and gradual abiotic change Thesecond captures the role of the biosphere inEarth-system functioning through the value rangedistribution and relative abundance of the func-tional traits of the organisms present in an eco-system or biota (7)For the first role the concept of phylogenetic

species variability (PSV) (7 33 37) would be anappropriate control variable However because

global data are not yet available for PSV we re-tain the global extinction rate as an interim con-trol variable although it is measured inaccuratelyand with a time lag There may be a considerablerisk in using extinction rate as a control variablebecause phylogenetic (and functional) diversitymay be more sensitive to human pressures thanspecies-level diversity (38) In principle the bound-ary should be set at a rate of loss of PSV no greaterthan the rate of evolution of new PSV during theHolocene Because that is unknown wemust fallback on the (imperfectly) known extinction rateof well-studied organisms over the past several

SCIENCE sciencemagorg 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 1259855-5

Earth-systemprocess

Controlvariable(s)

Planetary boundary(zone of uncertainty)

Current value ofcontrol variable

Land-systemchange(R2009same)

Global Area offorested land as of original forestcover

Biome Area offorested land as of potential forest

Global 75 (75ndash54) Valuesare a weighted average of thethree individual biomeboundaries and their uncertaintyzones

BiomeTropical 85 (85ndash60)Temperate 50 (50ndash30)Boreal 85 (85ndash60)

62

Freshwateruse(R2009Globalfreshwateruse)

Global Maximumamount ofconsumptive bluewater use (km3yrndash1)

Basin Blue waterwithdrawal as ofmean monthly riverflow

Global 4000 km3 yrndash1

(4000ndash6000 km3 yrndash1)

Basin Maximum monthlywithdrawal as a percentageof mean monthly river flowFor low-flow months 25(25ndash55) for intermediate-flow months 30 (30ndash60)for high-flow months 55(55ndash85)

~2600 km3 yrndash1

Atmosphericaerosolloading(R2009same)

Global AerosolOptical Depth(AOD) but muchregional variation

Regional AOD asa seasonal averageover a region SouthAsian Monsoonused as a case study

Regional (South AsianMonsoon as a case study)anthropogenic total (absorbingand scattering) AOD overIndian subcontinent of 025(025ndash050) absorbing(warming) AOD less than 10of total AOD

030 AOD overSouth Asianregion

Introductionof novel entities(R2009 Chemicalpollution)

No control variablecurrently defined

No boundary currentlyidentified but see boundaryfor stratospheric ozone for anexample of a boundaryrelated to a novel entity (CFCs)

RESEARCH | RESEARCH ARTICLE

million yearsmdashabout 1 per million species-years(39)mdashand add a large uncertainty bound raisingthe boundary to 10 permillion species-years Therisk is that although the Earth system can tol-erate a higher-than-background level of extinc-tions for a time we do not knowwhat levels of ortypes of biodiversity lossmay possibly trigger non-linear or irreversible changes to the Earth systemThe second control variable aims to capture the

role of the biosphere in Earth-system functioningand measures loss of biodiversity components atboth global and biomelarge ecosystem levels Al-though several variables have been developed atlocal scales for measuring functional diversity[eg (40)] finding an appropriate control varia-ble at regional or global levels is challenging Forthe present we propose an interim control var-iable the Biodiversity Intactness Index (BII) (41)BII assesses change in population abundance as aresult of human impacts such as land or resourceuse across a wide range of taxa and functionalgroups at a biome or ecosystem level using pre-industrial era abundance as a reference point Theindex typically ranges from 100 (abundancesacross all functional groups at preindustrial levels)to lower values that reflect the extent and degreeof human modification of populations of plantsand animals BII values for particular functionalgroups can go above 100 if humanmodificationsto ecosystems lead to increases in the abundanceof those speciesDue to a lack of evidence on the relationship

between BII and Earth-system responses we pro-

pose a preliminary boundary at 90 of the BIIbut with a very large uncertainty range (90 to30) that reflects the large gaps in our knowl-edge about the BIIndashEarth-system functioningrelationship (42 43) BII has been so far appliedto southern Africarsquos terrestrial biomes only (seefig S3 for an estimation of aggregated humanpressures on the terrestrial biosphere globally)where the index (not yet disaggregated to func-tional groups) was estimated to be 84 BIIranged from 69 to 91 for the seven countrieswhere it has been applied (41) Observations acrossthese countries suggest that decreases in BII ad-equately capture increasing levels of ecosystemdegradation defined as land uses that do not al-ter the land-cover type but lead to a persistentloss in ecosystem productivity (41)In addition to further work on functional mea-

sures such as BII in the longer term the conceptof biome integritymdashthe functioning and persist-ence of biomes at broad scales (7)mdashoffers a prom-ising approach and with further research couldprovide a set of operational control variables (oneper biome) that is appropriate robust and scien-tifically based

Stratospheric ozone depletion

We retain the original control variable [O3 con-centration in DU (Dobson units)] and boundary(275 DU) This boundary is only transgressedover Antarctica in the austral spring when O3

concentration drops to about 200 DU (44) How-ever the minimum O3 concentration has been

steady for about 15 years and is expected to riseover the coming decades as the ozone hole isrepaired after the phasing out of ozone-depletingsubstances This is an example in which after aboundary has been transgressed regionally hu-manity has taken effective action to return theprocess back to within the boundary

Ocean acidification

This boundary is intimately linked with one ofthe control variables CO2 for the climate changePB The concentration of free H+ ions in the sur-face ocean has increased by about 30 over thepast 200 years due to the increase in atmosphericCO2 (45) This in turn influences carbonate chem-istry in surface ocean waters Specifically it lowersthe saturation state of aragonite (Warag) a form ofcalcium carbonate formed by many marine orga-nisms At Warag lt 1 aragonite will dissolve Nonew evidence has emerged to suggest that theoriginally proposed boundary (ge80 of the pre-industrial average annual global Warag) shouldbe adjusted although geographical heterogeneityin Warag is important in monitoring the state ofthe boundary around the worldrsquos oceans (fig S4)Currently Warag is approximately equal to 84 ofthe preindustrial value (46) This boundary wouldnot be transgressed if the climate-change bound-ary of 350 ppm CO2 were to be respected

Biogeochemical flows

The original boundary was formulated for phos-phorus (P) and nitrogen (N) only but we nowpropose a more generic PB to encompass humaninfluence on biogeochemical flows in general Al-though the carbon cycle is covered in the climate-change boundary other elements such as silicon(47 48) are also important for Earth-system func-tioning Furthermore there is increasing evidencethat ratios between elements in the environmentmay have impacts on biodiversity on land and inthe sea (49ndash51) Thus we may ultimately need todevelop PBs for other elements and their ratiosalthough for now we focus on P and N onlyA two-level approach is now proposed for the

P component of the biogeochemical flows bound-ary (see also the supplementary materials) Theoriginal global-level boundary based on the pre-vention of a large-scale ocean anoxic event isretained with the proposed boundary set at asustained flow of 11 Tg P yearndash1 from freshwatersystems into the ocean Based on the analysis ofCarpenter and Bennett (3) we now propose anadditional regional-level P boundary designedto avert widespread eutrophication of freshwatersystems at a flow of 62 Tg P yearndash1 from fer-tilizers (mined P) to erodible soilsGiven that the addition of P to regional

watersheds is almost entirely from fertilizers theregional-level boundary applies primarily to theworldrsquos croplands The current global rate of ap-plication of P in fertilizers to croplands is 142 TgP yearndash1 (52 53) Observations point toward a fewagricultural regions of very high P applicationrates as the main contributors to the transgres-sion of this boundary (Fig 2 and fig S5A) andsuggest that a redistribution of P from areas

1259855-6 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 sciencemagorg SCIENCE

Fig 3The current status of the control variables for seven of the nine planetary boundaries Thegreen zone is the safe operating space (below the boundary) yellow represents the zone of uncertainty(increasing risk) and red is the high-risk zoneThe planetary boundary itself lies at the inner heavy circleThe control variables have been normalized for the zone of uncertainty (between the two heavy circles)the center of the figure therefore does not represent values of 0 for the control variables The controlvariable shown for climate change is atmospheric CO2 concentration Processes for which global-levelboundaries cannot yet be quantified are represented by gray wedges these are atmospheric aerosolloading novel entities and the functional role of biosphere integrity Modified from (1)

RESEARCH | RESEARCH ARTICLE

where it is currently in excess to areas where thesoil is naturally P-poormay simultaneously boostglobal crop production and reduce the transgres-sion of the regional-level P boundary (3 52 54)The N boundary has been taken from the com-

prehensive analysis of de Vries et al (5) whichproposed a PB for eutrophication of aquatic eco-systems of 62 Tg N yearndash1 from industrial andintentional biological N fixation using the moststringent water quality criterion As for the Pboundary a few agricultural regions of very highN application rates are the main contributors tothe transgression of this boundary (Fig 2 andfig S5B) This suggests that a redistribution of Ncould simultaneously boost global crop produc-tion and reduce the transgression of the regional-level boundaryBecause the major anthropogenic perturba-

tion of both the N and P cycles arises from fertil-izer application we can analyze the links betweenthe independently determined N and P bounda-ries in an integrated way based on the NP ratioin the growing plant tissue of agricultural cropsApplying this ratio which is on average 118 (55)to the P boundary (62 Tg P yearndash1) gives an Nboundary of 73 Tg N yearndash1 Conversely applyingthe ratio to theN boundary (62 TgN yearndash1) givesa P boundary of 53 Tg P yearndash1 The small dif-ferences between the boundaries derived usingthe NP ratio and those calculated independent-ly which are likely nonsignificant differencesgiven the precision of the data available for thecalculations show the internal consistency inour approach to the biogeochemical boundariesMore detail on the development of the P andN

boundaries is given in (33) where we also em-phasize that the proposed P and N boundariesmay be larger for an optimal allocation of N (andP) over the globe

Land-system change

The updated biosphere integrity boundary pro-vides a considerable constraint on the amountand pattern of land-system change in all ter-restrial biomes forests woodlands savannasgrasslands shrublands tundra and so on Theland-system change boundary is now focusedmore tightly on a specific constraint the biogeo-physical processes in land systems that directlyregulate climatemdashexchange of energy water andmomentum between the land surface and theatmosphere The control variable has been changedfrom the amount of cropland to the amount offorest cover remaining as the three major forestbiomesmdashtropical temperate and borealmdashplay astronger role in land surfacendashclimate couplingthan other biomes (56 57) In particular we fo-cus on those land-system changes that can in-fluence the climate in regions beyond the regionwhere the land-system change occurredOf the forest biomes tropical forests have sub-

stantial feedbacks to climate through changes inevapotranspiration when they are converted tononforested systems and changes in the distribu-tion of boreal forests affect the albedo of the landsurface and hence regional energy exchange Bothhave strong regional and global teleconnections

The biome-level boundary for these two types offorest have been set at 85 (Table 1 and thesupplementary materials) and the boundary fortemperate forests has been proposed at 50 ofpotential forest cover because changes to tem-perate forests are estimated to have weaker in-fluences on the climate system at the global levelthan changes to the other two major forestbiomes (56) These boundaries would almostsurely be met if the proposed biosphere integ-rity boundary of 90 BII were respectedEstimates of the current status of the land-

system change boundary are given in Figs 2 and3 and fig S6 and in (58)

Freshwater use

The revised freshwater use boundary has retainedconsumptive use of blue water [from rivers lakesreservoirs and renewable groundwater stores(59)] as the global-level control variable and4000 km3year as the value of the boundaryThis PB may be somewhat higher or lower de-pending on riversrsquo ecological flow requirements(6) Therefore we report here a new assessmentto complement the PB with a basin-scale bound-ary for the maximum rate of blue water with-drawal along rivers based on the amount of waterrequired in the river system to avoid regime shiftsin the functioning of flow-dependent ecosystemsWe base our control variable on the concept ofenvironmental water flows (EWF) which definesthe level of river flows for different hydrologicalcharacteristics of river basins adequate to main-tain a fair-to-good ecosystem state (60ndash62)The variable monthly flow (VMF) method

(33 63) was used to calculate the basin-scaleboundary for water This method takes accountof intra-annual variability by classifying flow re-gimes into high- intermediate- and low-flowmonths and allocating EWF as a percentage ofthe mean monthly flow (MMF) Based on thisanalysis the zones of uncertainty for the river-basin scale water boundary were set at 25 to 55of MMF for the low-flow regime 40 to 70 forthe intermediate-flow regime and 55 to 85 forthe high-flow regime (table S2) The boundarieswere set at the lower end of the uncertaintyranges that encompass average monthly EWFOur new estimates of the current status of thewater use boundarymdashcomputed based on gridcellndashspecific estimates of agricultural industrialand domestic water withdrawalsmdashare shown inFigs 2 and 3 with details in figs S7 and S8

Atmospheric aerosol loading

Aerosols have well-known serious human healtheffects leading to about 72 million deaths peryear (64) They also affect the functioning of theEarth system in many ways (65) (fig S9) Herewe focus on the effect of aerosols on regionalocean-atmosphere circulation as the rationalefor a separate aerosols boundary We adopt aero-sol optical depth (AOD) (33) as the control var-iable and use the south Asian monsoon as a casestudy based on the potential of widespread aero-sol loading over the Indian subcontinent to switchthe monsoon system to a drier state

The background AOD over south Asia is ~015and can be as high as 04 during volcanic events(66) Emissions of black carbon and organic car-bon from cooking and heating with biofuels andfrom diesel transportation and emission of sul-fates and nitrates from fossil fuel combustioncan increase seasonal mean AODs to as high as04 (larger during volcanic periods) leading todecreases of 10 to 15 of incident solar radiationat the surface (fig S9) A substantial decrease inmonsoon activity is likely around an AOD of 050an increase of 035 above the background (67)Taking a precautionary approach toward uncer-tainties surrounding the position of the tippingpoint we propose a boundary at an AOD of 025(an increase due to human activities of 01) witha zone of uncertainty of 025 to 050 The annualmean AOD is currently about 03 (66) within thezone of uncertainty

Introduction of novel entities

We define novel entities as new substances newforms of existing substances and modified lifeforms that have the potential for unwanted geo-physical andor biological effects Anthropogenicintroduction of novel entities to the environmentis of concern at the global level when these en-tities exhibit (i) persistence (ii) mobility acrossscales with consequent widespread distributionsand (iii) potential impacts on vital Earth-systemprocesses or subsystems These potentially in-clude chemicals and other new types of engi-neered materials or organisms [eg (68ndash71)] notpreviously known to the Earth system as well asnaturally occurring elements (for example heavymetals) mobilized by anthropogenic activitiesThe risks associated with the introduction ofnovel entities into the Earth system are exempli-fied by the release of CFCs (chlorofluorocarbons)which are very useful synthetic chemicals thatwere thought to be harmless but had unexpecteddramatic impacts on the stratospheric ozone layerIn effect humanity is repeatedly running suchglobal-scale experiments but not yet applying theinsights from previous experience to new appli-cations (72 73)Today there aremore than 100000 substances

in global commerce (74) If nanomaterials andplastic polymers that degrade to microplasticsare included the list is even longer There is alsoa ldquochemical intensificationrdquo due to the rapidlyincreasing global production of chemicals theexpanding worldwide distribution as chemicalproducts or in consumer goods and the exten-sive global trade in chemical wastes (75)In recent years there has been a growing de-

bate about the global-scale effects of chemicalpollution leading to calls for the definition ofcriteria to identify the kinds of chemical sub-stances that are likely to be globally problematic(76 77) Persson et al (73) proposed that there arethree conditions that need to be fulfilled for achemical to pose a threat to the Earth system (i)the chemical has an unknown disruptive effecton a vital Earth-systemprocess (ii) the disruptiveeffect is not discovered until it is a problem at theglobal scale and (iii) the effect is not readily

SCIENCE sciencemagorg 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 1259855-7

RESEARCH | RESEARCH ARTICLE

reversible The challenge to the research commu-nity is to develop the knowledge base that allowsthe screening of chemicals before they are re-leased into the environment for properties thatmay predispose them toward becoming globalproblemsAs a first step toward meeting this challenge

the three conditions outlined above have beenused as the basis for identifying scenarios ofchemical pollution that fulfill the conditions andas a next step for pinpointing chemical profilesthat fit the scenarios (28) This proposal consti-tutes a first attempt at adding the Earth-systemperspective when assessing hazard and risk ofchemicals and offers a vision for a systematic ap-proach to a complex management situation withmany unknownsDespite this progress in developing an Earth-

systemndashoriented approach there is not yet anaggregate global-level analysis of chemical pol-lution on which to base a control variable or aboundary value It may also serve little purposeto define boundary values and control varia-bles for a planetary boundary of this complexityNevertheless there is a potential threat fromnovel entities to disrupt the functioning of theEarth-system and society needs to learn how tomitigate these unknown risks and manage chem-icals under uncertainty (28 73)Some precautionary and preventive actions

can be considered These may include a strongerfocus on green chemistry (78) finding synergieswith risk-reducing interventions in other fieldssuch as occupational health (79) paying moreattention to learning from earlier mistakes (8081) and investing in science to better under-stand and monitor vital Earth-system processesin order to be able to detect disruptive effectsfrom novel entities as early as possible

Hierarchy of boundaries

An analysis of the many interactions among theboundaries (table S3 and fig S10) suggests thattwo of themmdashclimate change and biosphereintegritymdashare highly integrated emergent system-level phenomena that are connected to all of theother PBs They operate at the level of the wholeEarth system (7) and have coevolved for nearly4 billion years (82) They are regulated by theother boundaries and on the other hand pro-vide the planetary-level overarching systems with-in which the other boundary processes operateFurthermore large changes in the climate or inbiosphere integrity would likely on their ownpush the Earth system out of the Holocene stateIn fact transitions between time periods in Earthhistory have often been delineated by substantialshifts in climate the biosphere or both (82 83)These observations suggest a two-level hierar-

chy of boundaries in which climate change andbiosphere integrity should be recognized as coreplanetary boundaries through which the otherboundaries operate The crossing of one or moreof the other boundaries may seriously affect hu-man well-being and may predispose the trans-gression of a core boundary(ies) but does not byitself lead to a new state of the Earth system This

hierarchical approach to classifying the bounda-ries becomes clearer by examining inmore detailthe roles of climate and biosphere integrity in thefunctioning of the Earth systemThe climate system is a manifestation of the

amount distribution and net balance of energyat Earthrsquos surface The total amount of energysets the overall conditions for life In Earthrsquos cur-rent climate a range of global surface temper-atures and atmospheric pressures allows the threephases of water to be present simultaneouslywith ice and water vapor playing critical roles inthe physical feedbacks of the climate system Thedistribution of energy by latitude over the landand sea surfaces and within the ocean plays amajor role in the circulation of the two greatfluids the ocean and the atmosphere These sys-temic physical characteristics are key spatial de-terminants of the distribution of the biota andthe structure and functioning of ecosystems andare controllers of biogeochemical flowsBiosphere integrity is also crucial to Earth-

system functioning where the biosphere is de-fined as the totality of all ecosystems (terrestrialfreshwater andmarine) on Earth and their biota(32) These ecosystems and biota play a criticalrole in determining the state of the Earth systemregulating its material and energy flows and itsresponses to abrupt and gradual change (7) Di-versity in the biosphere provides resilience toterrestrial and marine ecosystems (83 84) Thebiosphere not only interacts with the other plan-etary boundaries but also increases the capacityof theEarth system topersist in a given state underchanges in these other boundaries The ultimatebasis for the many roles that the biosphere playsin Earth-system dynamics is the genetic code ofthe biota the basic information bank that de-fines the biospherersquos functional role and its ca-pacity to innovate and persist into the future

Planetary boundaries in asocietal context

A proposed approach for sustainable develop-ment goals (SDGs) (85) argues that the stablefunctioning of the Earth system is a prereq-uisite for thriving societies around the world Thisapproach implies that the PB framework orsomething like it will need to be implementedalongside the achievement of targets aimed atmore immediate human needs such as provi-sion of clean affordable and accessible energyand the adequate supply of food World devel-opment within the biophysical limits of a stableEarth system has always been a necessity [eg(86 87)] However only recently for a numberof reasons has it become possible to identifyevaluate and quantify risks of abrupt planetary-and biome-level shifts due to overshoot of keyEarth-system parameters (i) the emergence ofglobal-change thinking and Earth-system think-ing (88) (ii) the rise of ldquothe Planetaryrdquo as a rel-evant level of complex system understanding(89ndash92) and (iii) observable effects of the rapidincrease in human pressures on the planet (16)The PB approach is embedded in this emerg-

ing social context but it does not suggest how to

maneuver within the safe operating space in thequest for global sustainability For example thePB framework does not as yet account for the re-gional distribution of the impact or its histor-ical patterns Nor does the PB framework takeinto account the deeper issues of equity and cau-sation The current levels of the boundary pro-cesses and the transgressions of boundaries thathave already occurred are unevenly caused bydifferent human societies and different socialgroups The wealth benefits that these trans-gressions have brought are also unevenly distrib-uted socially and geographically It is easy toforesee that uneven distribution of causation andbenefits will continue and these differentialsmust surely be addressed for a Holocene-likeEarth-system state to be successfully legitimatedand maintained However the PB framework ascurrently construed provides no guidance as tohow this may be achieved [although some po-tential synergies have been noted (54)] and itcannot readily be used tomake choices betweenpathways for piecemeal maneuvering withinthe safe operating space ormore radical shifts ofglobal governance (93)The nature of the PB framework implies that

two important cautions should be observedwhenapplication of the framework to policy or man-agement is proposed boundary interactions andscale

Boundary interactions

The planetary boundaries framework arises fromthe scientific evidence that Earth is a singlecomplex integrated systemmdashthat is the bound-aries operate as an interdependent set [eg(94)] (table S1 and fig S10) Although a system-atic quantitative analysis of interactions amongall of the processes for which boundaries areproposed remains beyond the scope of currentmodeling and observational capacity the Earthsystem clearly operates in well-defined states inwhich these processes and their interactionscan create stabilizing or destabilizing feedbacks(16 90 95) This has profound implications forglobal sustainability because it emphasizes theneed to address multiple interacting environ-mental processes simultaneously (eg stabilizingthe climate system requires sustainable forestmanagement and stable ocean ecosystems)

Scale

The PB framework is not designed to be ldquodown-scaledrdquo or ldquodisaggregatedrdquo to smaller levels suchas nations or local communities That said thePB framework recognizes the importance ofchanges at the level of subsystems in the Earthsystem (eg biomes or large river basins) on thefunctioning of the Earth system as a whole Alsothere are strong arguments for an integrated ap-proach coupling boundary definitions at region-al and global levels with development goals toenable the application of ldquoPB thinkingrdquo at lev-els (nations basins and regions) where policyaction most commonly occurs [eg (85 96)]This update of the PB framework is one step on

a longer-term evolution of scientific knowledge to

1259855-8 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 sciencemagorg SCIENCE

RESEARCH | RESEARCH ARTICLE

inform and support global sustainability goalsand pathways This evolution is needed morethan ever before there are severe implementa-tion gaps inmany global environmental policiesrelating to the PB issues where problematictrends are not being halted or reversed despiteinternational consensus about the urgency of theproblems The prospect of tighter resource con-straints and rising environmental hazards is alsounavoidably turning the focus onto global socialequity and the planetary stewardship of Earthrsquoslife-support system There is a need for a trulyglobal evidence base with much greater integra-tion among issues in order to respond to theseglobal challenges New research initiatives [egFuture Earth (wwwfutureearthorg)] provide evi-dence that science can respond to this need byapplying Earth-system research to advance a newgeneration of integrated global analyses and toexplore options for transformations toward sus-tainability This is a clear sign that as the risksof the Anthropocene to human well-being be-come clearer research is maturing to a pointwhere a systemic step-change is possiblemdashandnecessarymdashin exploring and defining a safe andjust planetary operating space for the furtherdevelopment of human societies

Methods summary

Our approach to building the planetary bound-aries framework is described above We haveimplemented the framework through an ex-pert assessment and synthesis of the scientificknowledge of intrinsic biophysical processes thatregulate the stability of the Earth system Ourprecautionary approach is based on the main-tenance of a Holocene-like state of the Earthsystem and on an assessment of the level ofhuman-driven change that would risk destabi-lizing this state For the climate change PB thereis already much literature on which to basesuch an assessment For others such as strato-spheric ozone ocean acidification extinctionrates and P andN cycles we have used estimatesof preindustrial values of the control variableas a Holocene baseline Where large undesira-ble thresholds exist and have been studied (egpolar ice sheets Amazon rainforest aragonitedissolution atmospheric aerosols and the southAsian monsoon) quantitative boundaries can bereadily proposed For others where the focus ison erosion of Earth-system resilience the bound-aries are more difficult (but not impossible) toquantify as reflected in larger uncertainty zonesWe used large-scale assessments of the impacts

of human activities on Earth-system functioning[eg Intergovernmental Panel on Climate Change(17 18) the International Geosphere-BiosphereProgramme synthesis (16) and chemicals (75 80)]as sources of community-level understandingon which to propose PBs Our update has alsorelied on post-2009 assessments of individualboundaries by the relevant expert research com-munities examples include phosphorus (3) ni-trogen (5) biosphere integrity (7) freshwater use(5 63) and novel entities [with a focus on chem-icals (28 73)] Finally some new analyses have

been undertaken specifically for this paper (i) afreshwater-use PB based on the EWF approach(33 63) (ii) the linkage of the phosphorus andnitrogen boundaries via the NP ratio in grow-ing crop tissue (33) and (iii) the use of majorforest biomes as the basis for the land-systemchange PB (33)

REFERENCES AND NOTES

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2 J Rockstroumlm et al A safe operating space for humanityNature 461 472ndash475 (2009) doi 101038461472apmid 19779433

3 S R Carpenter E M Bennett Reconsideration of theplanetary boundary for phosphorus Environ Res Lett 6014009 (2011) doi 1010881748-932661014009

4 S W Running Ecology A measurable planetary boundaryfor the biosphere Science 337 1458ndash1459 (2012)doi 101126science1227620 pmid 22997311

5 W de Vries J Kros C Kroeze S P Seitzinger Assessingplanetary and regional nitrogen boundaries related to foodsecurity and adverse environmental impacts Curr OpinionEnviron Sust 5 392ndash402 (2013) doi 101016jcosust201307004

6 D Gerten et al Towards a revised planetary boundary forconsumptive freshwater use Role of environmental flowrequirements Curr Opinion Environ Sust 5 551ndash558 (2013)doi 101016jcosust201311001

7 G M Mace et al Approaches to defining a planetary boundaryfor biodiversity Glob Environ Change 28 289ndash297 (2014)doi 101016jgloenvcha201407009

8 V Galaz Global Environmental Governance Technology andPolitics The Anthropocene Gap (Edward Elgar CheltenhamUK 2014)

9 UN GSP (UN High-Level Panel on Global Sustainability)Resilient People Resilient Planet A Future Worth Choosing(Report for the 2012 Rio+20 Earth Summit United NationsNew York 2012)

10 WBCSD (World Business Council on Sustainable Development)Action 2020 Overview (WBCSD Geneva Switzerlandhttpaction2020org accessed 18 June 2014)

11 R Costanza L Graumlich W Steffen Eds Integrated Historyand Future of People on Earth (MIT Press CambridgeMA USA 2006)

12 S Soumlrlin P Warde in Naturersquos End History and theEnvironment S Soumlrlin P Warde Eds (Palgrave MacMillanLondon 2009) pp 1ndash19

13 R C Bishop Endangered species and uncertainty Theeconomics of a safe minimum standard Am J Agric Econ 6110ndash18 (1978) doi 1023071240156

14 T M Crowards Safe minimum standards Costs andopportunities Ecol Econ 25 303ndash314 (1998) doi 101016S0921-8009(97)00041-4

15 W Steffen J Crutzen J R McNeill The Anthropocene Arehumans now overwhelming the great forces of NatureAmbio 36 614ndash621 (2007) doi 1015790044-7447(2007)36[614TAAHNO]20CO2 pmid 18240674

16 W Steffen et al Global Change and the Earth System A PlanetUnder Pressure (The IGBP Book Series Springer-VerlagBerlin Heidelberg New York 2004)

17 IPCC (Intergovernmental Panel on Climate Change) Managingthe risks of extreme events and disasters to advanceclimate change adaptation A special report of Working GroupsI and II of the IPCC CB Field et al Eds (CambridgeUniversity Press Cambridge UK (2012) doi 101017CBO9781139177245

18 IPCC (Intergovernmental Panel on Climate Change) ClimateChange 2013 The Physical Science Basis Summary forPolicymakers L Alexander et al Eds (IPCC SecretariatGeneva Switzerland 2013) doi 101017CBO9781107415324

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20 K Richardson W Steffen D Liverman Climate Change GlobalRisks Challenges and Decisions (Cambridge Univ PressCambridge UK 2011)

21 T M Lenton et al Tipping elements in the Earthrsquos climatesystem Proc Natl Acad Sci USA 105 1786ndash1793 (2008)doi 101073pnas0705414105 pmid 18258748

22 M Scheffer et al Early-warning signals for criticaltransitions Nature 461 53ndash59 (2009) doi 101038nature08227 pmid 19727193

23 S R Carpenter W A Brock Rising variance A leadingindicator of ecological transition Ecol Lett 9 311ndash318 (2006)doi 101111j1461-0248200500877x pmid 16958897

24 J Bakke et al Rapid oceanic and atmospheric changes duringthe Younger Dryas cold period Nat Geosci 2 202ndash205(2009) doi 101038ngeo439

25 M Scheffer et al Anticipating critical transitions Science338 344ndash348 (2012) doi 101126science1225244pmid 23087241

26 R Wang et al Flickering gives early warning signals of acritical transition to a eutrophic lake state Nature 492419ndash422 (2012) doi 101038nature11655 pmid 23160492

27 R Biggs S R Carpenter W A Brock Turning back fromthe brink Detecting an impending regime shift in time to avertit Proc Natl Acad Sci USA 106 826ndash831 (2009)doi 101073pnas0811729106 pmid 19124774

28 M MacLeod et al Identifying chemicals that are planetaryboundary threats Environ Sci Technol 48 11057ndash11063(2014) doi 101021es501893m pmid 25181298

29 C S Holling Resilience and stability of ecological systemsAnnu Rev Ecol Syst 4 1ndash23 (1973) doi 101146annureves04110173000245

30 C Folke et al Resilience thinking Integrating resilienceadaptability and transformability Ecol Soc 15 20 (2010)wwwecologyandsocietyorgvol15iss4art20

31 T P Hughes S Carpenter J Rockstroumlm M SchefferB Walker Multiscale regime shifts and planetary boundariesTrends Ecol Evol 28 389ndash395 (2013) doi 101016jtree201305019 pmid 23769417

32 T M Lenton H T P Williams On the origin of planetary-scaletipping points Trends Ecol Evol 28 380ndash382 (2013)doi 101016jtree201306001 pmid 23777818

33 Supplementary text figures and tables are available onScience Online

34 NOAA (National Oceanic and Atmospheric Administration)NOAA-ESRL Annual CO2 Data accessed at httpco2noworgCurrent-CO2CO2-Nowannual-co2html (2014)

35 S E Perkins L V Alexander J Nairn Increasing frequencyintensity and duration of observed global heat waves and warmspells Geophys Res Lett 39 L20714 (2012) doi 1010292012GL053361

36 A Shepherd et al A reconciled estimate of ice-sheet massbalance Science 338 1183ndash1189 (2012) doi 101126science1228102 pmid 23197528

37 M R Helmus T J Bland C K Williams A R IvesPhylogenetic measures of biodiversity Am Nat 169 E68ndashE83(2007) doi 101086511334 pmid 17230400

38 S Drsquoagata et al Human-mediated loss of phylogeneticand functional diversity in coral reef fishes Curr Biol24 555ndash560 (2014) doi 101016jcub201401049pmid 24560574

39 A D Barnosky et al Has the Earthrsquos sixth mass extinctionalready arrived Nature 471 51ndash57 (2011) doi 101038nature09678 pmid 21368823

40 N W Mason F de Bello D Mouillot S Pavoine S Dray Aguide for using functional diversity indices to reveal changesin assembly processes along ecological gradients J VegSci 24 794ndash806 (2013) doi 101111jvs12013

41 R J Scholes R Biggs A biodiversity intactness index Nature434 45ndash49 (2005) doi 101038nature03289pmid 15744293

42 B Cardinale Ecology Impacts of biodiversity loss Science336 552ndash553 (2012) doi 101126science1222102pmid 22556243

43 D U Hooper et al A global synthesis reveals biodiversityloss as a major driver of ecosystem change Nature 486105ndash108 (2012) doi 101038nature11118pmid 22678289

44 BAS (British Antarctic Survey) ldquoAntarctic ozonerdquo wwwantarcticaacukmetjdsozoneindexhtmldata J ShanklinBritish Antarctic Survey (2013)

45 Royal Society Ocean Acidification Due to IncreasingAtmospheric Carbon Dioxide Policy Document 1205 (TheRoyal Society London 2005)

46 J M Guinotte V J Fabry Ocean acidification and its potentialeffects on marine ecosystems Ann N Y Acad Sci 1134320ndash342 (2008) doi 101196annals1439013pmid 18566099

47 D J Conley Terrestrial ecosystems and the globalbiogeochemical silica cycle Global Biogeochem Cycles 16681ndash688 (2002) doi 1010292002GB001894

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48 F Vandevenne E Struyf W Clymans P Meire Agriculturalsilica harvest Have humans created a new loop in the globalsilica cycle Front Ecol Environ 10 243ndash248 (2012)doi 101890110046

49 S E Gress T D Nichols C C Northcraft W T PeterjohnNutrient limitation in soils exhibiting differing nitrogenavailabilities What lies beyond nitrogen saturation Ecol 88119ndash130 (2007) doi 1018900012-9658(2007)88[119NLISED]20CO2 pmid 17489460

50 H Hillebrand V Lehmpfuhl Resource stoichiometry andconsumers control the biodiversity-productivity relationship inpelagic metacommunities Am Nat 178 171ndash181 (2011)doi 101086660831 pmid 21750381

51 C M Moore et al Processes and patterns of oceanic nutrientlimitation Nat Geosci 6 701ndash710 (2013) doi 101038ngeo1765

52 G K MacDonald E M Bennett P A Potter N RamankuttyAgronomic phosphorus imbalances across the worldrsquoscroplands Proc Natl Acad Sci USA 108 3086ndash3091 (2011)doi 101073pnas1010808108 pmid 21282605

53 L Bouwman et al Exploring global changes in nitrogen andphosphorus cycles in agriculture induced by livestockproduction over the 1900-2050 period Proc Natl AcadSci USA 110 20882ndash20887 (2013) doi 101073pnas1012878108 pmid 21576477

54 W Steffen M Stafford Smith Planetary boundaries equityand global sustainability Why wealthy countries could benefitfrom more equity Curr Opinion Environ Sust 5 403ndash408(2013) doi 101016jcosust201304007

55 D J Greenwood et al A unifying concept for the dependenceof whole-crop N P ratio on biomass theory and experimentAnn Bot (Lond) 102 967ndash977 (2008) doi 101093aobmcn188 pmid 18840873

56 P K Snyder C Delire J A Foley Evaluating the influence ofdifferent vegetation biomes on the global climate Clim Dyn23 279ndash302 (2004) doi 101007s00382-004-0430-0

57 P C West G T Narisma C C Barford C J KucharikJ A Foley An alternative approach for quantifying climateregulation by ecosystems Front Ecol Environ 9 126ndash133(2010) doi 101890090015

58 EPI (Earth Policy Institute) ldquoForest coverrdquo wwwearthpolicyorgindicatorsC56forests_2012_ (2014)

59 M Falkenmark Meeting water requirements of an expandingworld population Philos Trans R Soc Lond B Biol Sci 352929ndash936 (1997) doi 101098rstb19970072

60 J S Wallace M C Acreman C A Sullivan The sharing ofwater between society and ecosystems From conflict tocatchment-based co-management Philos Trans R Soc LondB Biol Sci 358 2011ndash2026 (2003) doi 101098rstb20031383 pmid 14728795

61 N L Poff et al The natural flow regime A paradigm for riverconservation and restoration BioSci 47 769ndash784 (1997)doi 1023071313099

62 N L Poff J K H Zimmerman Ecological responses to alteredflow regimes A literature review to inform the science andmanagement of environmental flows Biol 55 194ndash205 (2010)doi 101111j1365-2427200902272x

63 A V Pastor F Ludwig H Biemans H Hoff P KabatAccounting for environmental flow requirements in globalwater assessments Hydrol Earth Syst Sci 18 5041ndash5059(2014) doi 105194hess-18-5041-2014

64 WHO (World Health Organization) Burden of Disease from theJoint Effects of Household and Ambient Air Pollution for 2012(wwwwhointphehealth_topicsoutdoorairdatabasesFINAL_HAP_AAP_BoD24March2014pdf accessed 23 June 2014httpwwwwhointphehealth_topicsoutdoorairdatabasesen)

65 O Boucher et al in Climate Change 2013 The Physical ScienceBasis IPCC AR5 WGI report T Stocker et al Eds (CambridgeUniv Press Cambridge UK 2013) chap 7 pp 571ndash657

66 M Chin et al Multi-decadal aerosol variations from 1980 to2009 A perspective from observations and a global modelAtmos Chem Phys 14 3657ndash3690 (2014) doi 105194acp-14-3657-2014

67 V Ramanathan et al Atmospheric brown clouds Impacts onSouth Asian climate and hydrological cycle Proc Natl AcadSci USA 102 5326ndash5333 (2005) doi 101073pnas0500656102 pmid 15749818

68 M Cole P Lindeque C Halsband T S Galloway Microplasticsas contaminants in the marine environment A review MarPollut Bull 62 2588ndash2597 (2011) doi 101016jmarpolbul201109025 pmid 22001295

69 EEA (European Environment Agency) Genetically ModifiedOrganisms (GMOs) The Significance of Gene Flow ThroughPollen Transfer (Environmental Issue Report 28 EuropeanEnvironment Agency Copenhagen Denmark 2002)

70 J A Ivar do Sul M F Costa The present and future ofmicroplastic pollution in the marine environment Environ Pollut185 352ndash364 (2014) doi 101016jenvpol201310036pmid 24275078

71 R Kessler Engineered nanoparticles in consumer productsUnderstanding a new ingredient Environ Health Perspect 119a120ndasha125 (2011) doi 101289ehp119-a120 pmid 21356630

72 M Rees Our Final Century Will Civilisation Survive theTwenty-first Century (Arrow Books London 2003)

73 L M Persson et al Confronting unknown planetary boundarythreats from chemical pollution Environ Sci Technol 4712619ndash12622 (2013) doi 101021es402501c pmid 23980998

74 P P Egeghy et al The exposure data landscape formanufactured chemicals Sci Total Environ 414 159ndash166(2012) doi 101016jscitotenv201110046 pmid 22104386

75 UNEP (United Nations Environment Programme) GCOGlobal Chemicals Outlook Towards Sound Management ofChemicals (United Nations Environment ProgrammeNairobi Kenya 2013)

76 S Strempel M Scheringer C A Ng K HungerbuumlhlerScreening for PBT chemicals among the ldquoexistingrdquo andldquonewrdquo chemicals of the EU Environ Sci Technol 465680ndash5687 (2012) doi 101021es3002713pmid 22494215

77 M Scheringer et al How many persistent organic pollutantsshould we expect Atmos Poll Res 3 383ndash391 (2012)doi 105094APR2012044

78 K Sanderson Chemistry Itrsquos not easy being green Nature469 18ndash20 (2011) doi 101038469018a pmid 21209638

79 P A Schulte et al Occupational safety and health greenchemistry and sustainability A review of areas ofconvergence Environ Health 12 31 (2013) doi 1011861476-069X-12-31 pmid 23587312

80 EEA (European Environment Agency) Late Lessons from EarlyWarnings The Precautionary Principle 1896-2000 (EnvironmentalIssue Report 222001 Copenhagen Denmark 2001)

81 D Gee Late lessons from early warnings Toward realism andprecaution with endocrine-disrupting substances EnvironHealth Perspect 114 (suppl 1) 152ndash160 (2006) doi 101289ehp8134 pmid 16818262

82 T Lenton A Watson A Revolutions That Made the Earth(Oxford Univ Press Oxford UK 2011)

83 R Biggs et al Toward principles for enhancing the resilienceof ecosystem services Annu Rev Environ Resour 37421ndash448 (2012) doi 101146annurev-environ-051211-123836

84 G S Cumming P Olsson F S Chapin III C S HollingResilience experimentation and scale mismatches in social-ecological systems Landscape Ecol 28 1139ndash1150 (2013)doi 101007s10980-012-9725-4

85 D Griggs et al Policy Sustainable development goals forpeople and planet Nature 495 305ndash307 (2013) doi 101038495305a pmid 23518546

86 R Costanza Ed Ecological Economics The Science andManagement of Sustainability (Columbia Univ PressNew York 1991)

87 C Folke in Linking the Natural Environment and the EconomyEssays from the Eco-Eco Group C Folke T Karingberger Eds(Kluwer Academic Publishers Dordrecht Netherlands 1991)pp 77ndash94

88 L Robin S Soumlrlin P Warde Eds The Future of NatureDocuments of Global Change (Yale Univ Press New Haven CT2013)

89 U Heise Sense of Place and Sense of Planet TheEnvironmental Imagination of the Global (Oxford Univ PressOxford 2008)

90 M Scheffer Critical Transitions in Nature and Society(Princeton Univ Press Princeton NJ 2009)

91 J Masco Bad weather On planetary crisis Soc Stud Sci 407ndash40 (2010) doi 1011770306312709341598

92 G Paacutelsson et al Reconceptualizing the lsquoAnthroposrsquo in theAnthropocene Integrating the social sciences and humanitiesin global environmental change research Environ Sci Policy28 4 (2013) doi 101016jenvsci201211004

93 N Castree et al Changing the intellectual climate NatureClim Change 4 763ndash768 (2014) doi 101038nclimate2339

94 J M Anderies S R Carpenter W Steffen J Rockstroumlm Thetopology of non-linear global carbon dynamics From tippingpoints to planetary boundaries Environ Res Lett 8 044048(2013) doi 1010881748-932684044048

95 S E Cornell I C Prentice J I House C J DownyUnderstanding the Earth System Global Change Science forApplication (Cambridge Univ Press Cambridge 2012)

96 J A Dearing et al Safe and just operating spaces for regionalsocial-ecological systems Glob Environ Change 28 227ndash238(2014) doi 101016jgloenvcha201406012

ACKNOWLEDGMENTS

We thank J Foley and N Ramunkutty for contributions to theland-system change boundary A Pastor for analytical work on thePB for freshwater B Armstrong C Butler T McMichael andA Woodward for contributions to the novel entities boundary andB Scholes for comments on an earlier version of the manuscriptData associated with the paper are located at the StockholmResilience Centre Sweden (httpwwwstockholmresilienceorg21researchresearch-programmesplanetary-boundarieshtml)The planetary boundaries research at the Stockholm ResilienceCentre is made possible through a core grant from MISTRA(Swedish Foundation for Strategic Environmental Research) SECis supported by the Swedish Research Council EMB is supportedby the Natural Sciences and Engineering Research Council ofCanada and by the Trottier Institute for Science and Public PolicyRB is supported by a Branco Weiss Fellowship CF is supportedby the Family Erling Persson Academy Programme on GlobalEconomic Dynamics and the Biosphere IF is supported by theStordalen Foundation (Norway) SS is supported by theRiksbanken Jubileumsfond and the Institute for Advanced StudyPrinceton NJ and SRC and VR are supported bythe US National Science Foundation

SUPPLEMENTARY MATERIALS

wwwsciencemagorgcontent34762231259855supplDC1MethodsFigs S1 to S10Tables S1 to S3References (97ndash158)

11 August 2014 accepted 8 January 2015Published online 15 January 2015101126science1259855

1259855-10 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 sciencemagorg SCIENCE

RESEARCH | RESEARCH ARTICLE

DOI 101126science1259855 (2015)347 Science

et alWill SteffenplanetPlanetary boundaries Guiding human development on a changing

This copy is for your personal non-commercial use only

clicking herecolleagues clients or customers by you can order high-quality copies for yourIf you wish to distribute this article to others

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can be obtained byPermission to republish or repurpose articles or portions of articles

) February 12 2015 wwwsciencemagorg (this information is current as of

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including high-resolution figures can be found in the onlineUpdated information and services

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subject collectionsThis article appears in the following

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CopyrightAmerican Association for the Advancement of Science 1200 New York Avenue NW Washington DC 20005 (print ISSN 0036-8075 online ISSN 1095-9203) is published weekly except the last week in December by theScience

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million yearsmdashabout 1 per million species-years(39)mdashand add a large uncertainty bound raisingthe boundary to 10 permillion species-years Therisk is that although the Earth system can tol-erate a higher-than-background level of extinc-tions for a time we do not knowwhat levels of ortypes of biodiversity lossmay possibly trigger non-linear or irreversible changes to the Earth systemThe second control variable aims to capture the

role of the biosphere in Earth-system functioningand measures loss of biodiversity components atboth global and biomelarge ecosystem levels Al-though several variables have been developed atlocal scales for measuring functional diversity[eg (40)] finding an appropriate control varia-ble at regional or global levels is challenging Forthe present we propose an interim control var-iable the Biodiversity Intactness Index (BII) (41)BII assesses change in population abundance as aresult of human impacts such as land or resourceuse across a wide range of taxa and functionalgroups at a biome or ecosystem level using pre-industrial era abundance as a reference point Theindex typically ranges from 100 (abundancesacross all functional groups at preindustrial levels)to lower values that reflect the extent and degreeof human modification of populations of plantsand animals BII values for particular functionalgroups can go above 100 if humanmodificationsto ecosystems lead to increases in the abundanceof those speciesDue to a lack of evidence on the relationship

between BII and Earth-system responses we pro-

pose a preliminary boundary at 90 of the BIIbut with a very large uncertainty range (90 to30) that reflects the large gaps in our knowl-edge about the BIIndashEarth-system functioningrelationship (42 43) BII has been so far appliedto southern Africarsquos terrestrial biomes only (seefig S3 for an estimation of aggregated humanpressures on the terrestrial biosphere globally)where the index (not yet disaggregated to func-tional groups) was estimated to be 84 BIIranged from 69 to 91 for the seven countrieswhere it has been applied (41) Observations acrossthese countries suggest that decreases in BII ad-equately capture increasing levels of ecosystemdegradation defined as land uses that do not al-ter the land-cover type but lead to a persistentloss in ecosystem productivity (41)In addition to further work on functional mea-

sures such as BII in the longer term the conceptof biome integritymdashthe functioning and persist-ence of biomes at broad scales (7)mdashoffers a prom-ising approach and with further research couldprovide a set of operational control variables (oneper biome) that is appropriate robust and scien-tifically based

Stratospheric ozone depletion

We retain the original control variable [O3 con-centration in DU (Dobson units)] and boundary(275 DU) This boundary is only transgressedover Antarctica in the austral spring when O3

concentration drops to about 200 DU (44) How-ever the minimum O3 concentration has been

steady for about 15 years and is expected to riseover the coming decades as the ozone hole isrepaired after the phasing out of ozone-depletingsubstances This is an example in which after aboundary has been transgressed regionally hu-manity has taken effective action to return theprocess back to within the boundary

Ocean acidification

This boundary is intimately linked with one ofthe control variables CO2 for the climate changePB The concentration of free H+ ions in the sur-face ocean has increased by about 30 over thepast 200 years due to the increase in atmosphericCO2 (45) This in turn influences carbonate chem-istry in surface ocean waters Specifically it lowersthe saturation state of aragonite (Warag) a form ofcalcium carbonate formed by many marine orga-nisms At Warag lt 1 aragonite will dissolve Nonew evidence has emerged to suggest that theoriginally proposed boundary (ge80 of the pre-industrial average annual global Warag) shouldbe adjusted although geographical heterogeneityin Warag is important in monitoring the state ofthe boundary around the worldrsquos oceans (fig S4)Currently Warag is approximately equal to 84 ofthe preindustrial value (46) This boundary wouldnot be transgressed if the climate-change bound-ary of 350 ppm CO2 were to be respected

Biogeochemical flows

The original boundary was formulated for phos-phorus (P) and nitrogen (N) only but we nowpropose a more generic PB to encompass humaninfluence on biogeochemical flows in general Al-though the carbon cycle is covered in the climate-change boundary other elements such as silicon(47 48) are also important for Earth-system func-tioning Furthermore there is increasing evidencethat ratios between elements in the environmentmay have impacts on biodiversity on land and inthe sea (49ndash51) Thus we may ultimately need todevelop PBs for other elements and their ratiosalthough for now we focus on P and N onlyA two-level approach is now proposed for the

P component of the biogeochemical flows bound-ary (see also the supplementary materials) Theoriginal global-level boundary based on the pre-vention of a large-scale ocean anoxic event isretained with the proposed boundary set at asustained flow of 11 Tg P yearndash1 from freshwatersystems into the ocean Based on the analysis ofCarpenter and Bennett (3) we now propose anadditional regional-level P boundary designedto avert widespread eutrophication of freshwatersystems at a flow of 62 Tg P yearndash1 from fer-tilizers (mined P) to erodible soilsGiven that the addition of P to regional

watersheds is almost entirely from fertilizers theregional-level boundary applies primarily to theworldrsquos croplands The current global rate of ap-plication of P in fertilizers to croplands is 142 TgP yearndash1 (52 53) Observations point toward a fewagricultural regions of very high P applicationrates as the main contributors to the transgres-sion of this boundary (Fig 2 and fig S5A) andsuggest that a redistribution of P from areas

1259855-6 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 sciencemagorg SCIENCE

Fig 3The current status of the control variables for seven of the nine planetary boundaries Thegreen zone is the safe operating space (below the boundary) yellow represents the zone of uncertainty(increasing risk) and red is the high-risk zoneThe planetary boundary itself lies at the inner heavy circleThe control variables have been normalized for the zone of uncertainty (between the two heavy circles)the center of the figure therefore does not represent values of 0 for the control variables The controlvariable shown for climate change is atmospheric CO2 concentration Processes for which global-levelboundaries cannot yet be quantified are represented by gray wedges these are atmospheric aerosolloading novel entities and the functional role of biosphere integrity Modified from (1)

RESEARCH | RESEARCH ARTICLE

where it is currently in excess to areas where thesoil is naturally P-poormay simultaneously boostglobal crop production and reduce the transgres-sion of the regional-level P boundary (3 52 54)The N boundary has been taken from the com-

prehensive analysis of de Vries et al (5) whichproposed a PB for eutrophication of aquatic eco-systems of 62 Tg N yearndash1 from industrial andintentional biological N fixation using the moststringent water quality criterion As for the Pboundary a few agricultural regions of very highN application rates are the main contributors tothe transgression of this boundary (Fig 2 andfig S5B) This suggests that a redistribution of Ncould simultaneously boost global crop produc-tion and reduce the transgression of the regional-level boundaryBecause the major anthropogenic perturba-

tion of both the N and P cycles arises from fertil-izer application we can analyze the links betweenthe independently determined N and P bounda-ries in an integrated way based on the NP ratioin the growing plant tissue of agricultural cropsApplying this ratio which is on average 118 (55)to the P boundary (62 Tg P yearndash1) gives an Nboundary of 73 Tg N yearndash1 Conversely applyingthe ratio to theN boundary (62 TgN yearndash1) givesa P boundary of 53 Tg P yearndash1 The small dif-ferences between the boundaries derived usingthe NP ratio and those calculated independent-ly which are likely nonsignificant differencesgiven the precision of the data available for thecalculations show the internal consistency inour approach to the biogeochemical boundariesMore detail on the development of the P andN

boundaries is given in (33) where we also em-phasize that the proposed P and N boundariesmay be larger for an optimal allocation of N (andP) over the globe

Land-system change

The updated biosphere integrity boundary pro-vides a considerable constraint on the amountand pattern of land-system change in all ter-restrial biomes forests woodlands savannasgrasslands shrublands tundra and so on Theland-system change boundary is now focusedmore tightly on a specific constraint the biogeo-physical processes in land systems that directlyregulate climatemdashexchange of energy water andmomentum between the land surface and theatmosphere The control variable has been changedfrom the amount of cropland to the amount offorest cover remaining as the three major forestbiomesmdashtropical temperate and borealmdashplay astronger role in land surfacendashclimate couplingthan other biomes (56 57) In particular we fo-cus on those land-system changes that can in-fluence the climate in regions beyond the regionwhere the land-system change occurredOf the forest biomes tropical forests have sub-

stantial feedbacks to climate through changes inevapotranspiration when they are converted tononforested systems and changes in the distribu-tion of boreal forests affect the albedo of the landsurface and hence regional energy exchange Bothhave strong regional and global teleconnections

The biome-level boundary for these two types offorest have been set at 85 (Table 1 and thesupplementary materials) and the boundary fortemperate forests has been proposed at 50 ofpotential forest cover because changes to tem-perate forests are estimated to have weaker in-fluences on the climate system at the global levelthan changes to the other two major forestbiomes (56) These boundaries would almostsurely be met if the proposed biosphere integ-rity boundary of 90 BII were respectedEstimates of the current status of the land-

system change boundary are given in Figs 2 and3 and fig S6 and in (58)

Freshwater use

The revised freshwater use boundary has retainedconsumptive use of blue water [from rivers lakesreservoirs and renewable groundwater stores(59)] as the global-level control variable and4000 km3year as the value of the boundaryThis PB may be somewhat higher or lower de-pending on riversrsquo ecological flow requirements(6) Therefore we report here a new assessmentto complement the PB with a basin-scale bound-ary for the maximum rate of blue water with-drawal along rivers based on the amount of waterrequired in the river system to avoid regime shiftsin the functioning of flow-dependent ecosystemsWe base our control variable on the concept ofenvironmental water flows (EWF) which definesthe level of river flows for different hydrologicalcharacteristics of river basins adequate to main-tain a fair-to-good ecosystem state (60ndash62)The variable monthly flow (VMF) method

(33 63) was used to calculate the basin-scaleboundary for water This method takes accountof intra-annual variability by classifying flow re-gimes into high- intermediate- and low-flowmonths and allocating EWF as a percentage ofthe mean monthly flow (MMF) Based on thisanalysis the zones of uncertainty for the river-basin scale water boundary were set at 25 to 55of MMF for the low-flow regime 40 to 70 forthe intermediate-flow regime and 55 to 85 forthe high-flow regime (table S2) The boundarieswere set at the lower end of the uncertaintyranges that encompass average monthly EWFOur new estimates of the current status of thewater use boundarymdashcomputed based on gridcellndashspecific estimates of agricultural industrialand domestic water withdrawalsmdashare shown inFigs 2 and 3 with details in figs S7 and S8

Atmospheric aerosol loading

Aerosols have well-known serious human healtheffects leading to about 72 million deaths peryear (64) They also affect the functioning of theEarth system in many ways (65) (fig S9) Herewe focus on the effect of aerosols on regionalocean-atmosphere circulation as the rationalefor a separate aerosols boundary We adopt aero-sol optical depth (AOD) (33) as the control var-iable and use the south Asian monsoon as a casestudy based on the potential of widespread aero-sol loading over the Indian subcontinent to switchthe monsoon system to a drier state

The background AOD over south Asia is ~015and can be as high as 04 during volcanic events(66) Emissions of black carbon and organic car-bon from cooking and heating with biofuels andfrom diesel transportation and emission of sul-fates and nitrates from fossil fuel combustioncan increase seasonal mean AODs to as high as04 (larger during volcanic periods) leading todecreases of 10 to 15 of incident solar radiationat the surface (fig S9) A substantial decrease inmonsoon activity is likely around an AOD of 050an increase of 035 above the background (67)Taking a precautionary approach toward uncer-tainties surrounding the position of the tippingpoint we propose a boundary at an AOD of 025(an increase due to human activities of 01) witha zone of uncertainty of 025 to 050 The annualmean AOD is currently about 03 (66) within thezone of uncertainty

Introduction of novel entities

We define novel entities as new substances newforms of existing substances and modified lifeforms that have the potential for unwanted geo-physical andor biological effects Anthropogenicintroduction of novel entities to the environmentis of concern at the global level when these en-tities exhibit (i) persistence (ii) mobility acrossscales with consequent widespread distributionsand (iii) potential impacts on vital Earth-systemprocesses or subsystems These potentially in-clude chemicals and other new types of engi-neered materials or organisms [eg (68ndash71)] notpreviously known to the Earth system as well asnaturally occurring elements (for example heavymetals) mobilized by anthropogenic activitiesThe risks associated with the introduction ofnovel entities into the Earth system are exempli-fied by the release of CFCs (chlorofluorocarbons)which are very useful synthetic chemicals thatwere thought to be harmless but had unexpecteddramatic impacts on the stratospheric ozone layerIn effect humanity is repeatedly running suchglobal-scale experiments but not yet applying theinsights from previous experience to new appli-cations (72 73)Today there aremore than 100000 substances

in global commerce (74) If nanomaterials andplastic polymers that degrade to microplasticsare included the list is even longer There is alsoa ldquochemical intensificationrdquo due to the rapidlyincreasing global production of chemicals theexpanding worldwide distribution as chemicalproducts or in consumer goods and the exten-sive global trade in chemical wastes (75)In recent years there has been a growing de-

bate about the global-scale effects of chemicalpollution leading to calls for the definition ofcriteria to identify the kinds of chemical sub-stances that are likely to be globally problematic(76 77) Persson et al (73) proposed that there arethree conditions that need to be fulfilled for achemical to pose a threat to the Earth system (i)the chemical has an unknown disruptive effecton a vital Earth-systemprocess (ii) the disruptiveeffect is not discovered until it is a problem at theglobal scale and (iii) the effect is not readily

SCIENCE sciencemagorg 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 1259855-7

RESEARCH | RESEARCH ARTICLE

reversible The challenge to the research commu-nity is to develop the knowledge base that allowsthe screening of chemicals before they are re-leased into the environment for properties thatmay predispose them toward becoming globalproblemsAs a first step toward meeting this challenge

the three conditions outlined above have beenused as the basis for identifying scenarios ofchemical pollution that fulfill the conditions andas a next step for pinpointing chemical profilesthat fit the scenarios (28) This proposal consti-tutes a first attempt at adding the Earth-systemperspective when assessing hazard and risk ofchemicals and offers a vision for a systematic ap-proach to a complex management situation withmany unknownsDespite this progress in developing an Earth-

systemndashoriented approach there is not yet anaggregate global-level analysis of chemical pol-lution on which to base a control variable or aboundary value It may also serve little purposeto define boundary values and control varia-bles for a planetary boundary of this complexityNevertheless there is a potential threat fromnovel entities to disrupt the functioning of theEarth-system and society needs to learn how tomitigate these unknown risks and manage chem-icals under uncertainty (28 73)Some precautionary and preventive actions

can be considered These may include a strongerfocus on green chemistry (78) finding synergieswith risk-reducing interventions in other fieldssuch as occupational health (79) paying moreattention to learning from earlier mistakes (8081) and investing in science to better under-stand and monitor vital Earth-system processesin order to be able to detect disruptive effectsfrom novel entities as early as possible

Hierarchy of boundaries

An analysis of the many interactions among theboundaries (table S3 and fig S10) suggests thattwo of themmdashclimate change and biosphereintegritymdashare highly integrated emergent system-level phenomena that are connected to all of theother PBs They operate at the level of the wholeEarth system (7) and have coevolved for nearly4 billion years (82) They are regulated by theother boundaries and on the other hand pro-vide the planetary-level overarching systems with-in which the other boundary processes operateFurthermore large changes in the climate or inbiosphere integrity would likely on their ownpush the Earth system out of the Holocene stateIn fact transitions between time periods in Earthhistory have often been delineated by substantialshifts in climate the biosphere or both (82 83)These observations suggest a two-level hierar-

chy of boundaries in which climate change andbiosphere integrity should be recognized as coreplanetary boundaries through which the otherboundaries operate The crossing of one or moreof the other boundaries may seriously affect hu-man well-being and may predispose the trans-gression of a core boundary(ies) but does not byitself lead to a new state of the Earth system This

hierarchical approach to classifying the bounda-ries becomes clearer by examining inmore detailthe roles of climate and biosphere integrity in thefunctioning of the Earth systemThe climate system is a manifestation of the

amount distribution and net balance of energyat Earthrsquos surface The total amount of energysets the overall conditions for life In Earthrsquos cur-rent climate a range of global surface temper-atures and atmospheric pressures allows the threephases of water to be present simultaneouslywith ice and water vapor playing critical roles inthe physical feedbacks of the climate system Thedistribution of energy by latitude over the landand sea surfaces and within the ocean plays amajor role in the circulation of the two greatfluids the ocean and the atmosphere These sys-temic physical characteristics are key spatial de-terminants of the distribution of the biota andthe structure and functioning of ecosystems andare controllers of biogeochemical flowsBiosphere integrity is also crucial to Earth-

system functioning where the biosphere is de-fined as the totality of all ecosystems (terrestrialfreshwater andmarine) on Earth and their biota(32) These ecosystems and biota play a criticalrole in determining the state of the Earth systemregulating its material and energy flows and itsresponses to abrupt and gradual change (7) Di-versity in the biosphere provides resilience toterrestrial and marine ecosystems (83 84) Thebiosphere not only interacts with the other plan-etary boundaries but also increases the capacityof theEarth system topersist in a given state underchanges in these other boundaries The ultimatebasis for the many roles that the biosphere playsin Earth-system dynamics is the genetic code ofthe biota the basic information bank that de-fines the biospherersquos functional role and its ca-pacity to innovate and persist into the future

Planetary boundaries in asocietal context

A proposed approach for sustainable develop-ment goals (SDGs) (85) argues that the stablefunctioning of the Earth system is a prereq-uisite for thriving societies around the world Thisapproach implies that the PB framework orsomething like it will need to be implementedalongside the achievement of targets aimed atmore immediate human needs such as provi-sion of clean affordable and accessible energyand the adequate supply of food World devel-opment within the biophysical limits of a stableEarth system has always been a necessity [eg(86 87)] However only recently for a numberof reasons has it become possible to identifyevaluate and quantify risks of abrupt planetary-and biome-level shifts due to overshoot of keyEarth-system parameters (i) the emergence ofglobal-change thinking and Earth-system think-ing (88) (ii) the rise of ldquothe Planetaryrdquo as a rel-evant level of complex system understanding(89ndash92) and (iii) observable effects of the rapidincrease in human pressures on the planet (16)The PB approach is embedded in this emerg-

ing social context but it does not suggest how to

maneuver within the safe operating space in thequest for global sustainability For example thePB framework does not as yet account for the re-gional distribution of the impact or its histor-ical patterns Nor does the PB framework takeinto account the deeper issues of equity and cau-sation The current levels of the boundary pro-cesses and the transgressions of boundaries thathave already occurred are unevenly caused bydifferent human societies and different socialgroups The wealth benefits that these trans-gressions have brought are also unevenly distrib-uted socially and geographically It is easy toforesee that uneven distribution of causation andbenefits will continue and these differentialsmust surely be addressed for a Holocene-likeEarth-system state to be successfully legitimatedand maintained However the PB framework ascurrently construed provides no guidance as tohow this may be achieved [although some po-tential synergies have been noted (54)] and itcannot readily be used tomake choices betweenpathways for piecemeal maneuvering withinthe safe operating space ormore radical shifts ofglobal governance (93)The nature of the PB framework implies that

two important cautions should be observedwhenapplication of the framework to policy or man-agement is proposed boundary interactions andscale

Boundary interactions

The planetary boundaries framework arises fromthe scientific evidence that Earth is a singlecomplex integrated systemmdashthat is the bound-aries operate as an interdependent set [eg(94)] (table S1 and fig S10) Although a system-atic quantitative analysis of interactions amongall of the processes for which boundaries areproposed remains beyond the scope of currentmodeling and observational capacity the Earthsystem clearly operates in well-defined states inwhich these processes and their interactionscan create stabilizing or destabilizing feedbacks(16 90 95) This has profound implications forglobal sustainability because it emphasizes theneed to address multiple interacting environ-mental processes simultaneously (eg stabilizingthe climate system requires sustainable forestmanagement and stable ocean ecosystems)

Scale

The PB framework is not designed to be ldquodown-scaledrdquo or ldquodisaggregatedrdquo to smaller levels suchas nations or local communities That said thePB framework recognizes the importance ofchanges at the level of subsystems in the Earthsystem (eg biomes or large river basins) on thefunctioning of the Earth system as a whole Alsothere are strong arguments for an integrated ap-proach coupling boundary definitions at region-al and global levels with development goals toenable the application of ldquoPB thinkingrdquo at lev-els (nations basins and regions) where policyaction most commonly occurs [eg (85 96)]This update of the PB framework is one step on

a longer-term evolution of scientific knowledge to

1259855-8 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 sciencemagorg SCIENCE

RESEARCH | RESEARCH ARTICLE

inform and support global sustainability goalsand pathways This evolution is needed morethan ever before there are severe implementa-tion gaps inmany global environmental policiesrelating to the PB issues where problematictrends are not being halted or reversed despiteinternational consensus about the urgency of theproblems The prospect of tighter resource con-straints and rising environmental hazards is alsounavoidably turning the focus onto global socialequity and the planetary stewardship of Earthrsquoslife-support system There is a need for a trulyglobal evidence base with much greater integra-tion among issues in order to respond to theseglobal challenges New research initiatives [egFuture Earth (wwwfutureearthorg)] provide evi-dence that science can respond to this need byapplying Earth-system research to advance a newgeneration of integrated global analyses and toexplore options for transformations toward sus-tainability This is a clear sign that as the risksof the Anthropocene to human well-being be-come clearer research is maturing to a pointwhere a systemic step-change is possiblemdashandnecessarymdashin exploring and defining a safe andjust planetary operating space for the furtherdevelopment of human societies

Methods summary

Our approach to building the planetary bound-aries framework is described above We haveimplemented the framework through an ex-pert assessment and synthesis of the scientificknowledge of intrinsic biophysical processes thatregulate the stability of the Earth system Ourprecautionary approach is based on the main-tenance of a Holocene-like state of the Earthsystem and on an assessment of the level ofhuman-driven change that would risk destabi-lizing this state For the climate change PB thereis already much literature on which to basesuch an assessment For others such as strato-spheric ozone ocean acidification extinctionrates and P andN cycles we have used estimatesof preindustrial values of the control variableas a Holocene baseline Where large undesira-ble thresholds exist and have been studied (egpolar ice sheets Amazon rainforest aragonitedissolution atmospheric aerosols and the southAsian monsoon) quantitative boundaries can bereadily proposed For others where the focus ison erosion of Earth-system resilience the bound-aries are more difficult (but not impossible) toquantify as reflected in larger uncertainty zonesWe used large-scale assessments of the impacts

of human activities on Earth-system functioning[eg Intergovernmental Panel on Climate Change(17 18) the International Geosphere-BiosphereProgramme synthesis (16) and chemicals (75 80)]as sources of community-level understandingon which to propose PBs Our update has alsorelied on post-2009 assessments of individualboundaries by the relevant expert research com-munities examples include phosphorus (3) ni-trogen (5) biosphere integrity (7) freshwater use(5 63) and novel entities [with a focus on chem-icals (28 73)] Finally some new analyses have

been undertaken specifically for this paper (i) afreshwater-use PB based on the EWF approach(33 63) (ii) the linkage of the phosphorus andnitrogen boundaries via the NP ratio in grow-ing crop tissue (33) and (iii) the use of majorforest biomes as the basis for the land-systemchange PB (33)

REFERENCES AND NOTES

1 J Rockstroumlm et al Planetary boundaries Exploring the safeoperating space for humanity Ecol Soc 14 32 (2009)httpwwwecologyandsocietyorgvol14iss2art32

2 J Rockstroumlm et al A safe operating space for humanityNature 461 472ndash475 (2009) doi 101038461472apmid 19779433

3 S R Carpenter E M Bennett Reconsideration of theplanetary boundary for phosphorus Environ Res Lett 6014009 (2011) doi 1010881748-932661014009

4 S W Running Ecology A measurable planetary boundaryfor the biosphere Science 337 1458ndash1459 (2012)doi 101126science1227620 pmid 22997311

5 W de Vries J Kros C Kroeze S P Seitzinger Assessingplanetary and regional nitrogen boundaries related to foodsecurity and adverse environmental impacts Curr OpinionEnviron Sust 5 392ndash402 (2013) doi 101016jcosust201307004

6 D Gerten et al Towards a revised planetary boundary forconsumptive freshwater use Role of environmental flowrequirements Curr Opinion Environ Sust 5 551ndash558 (2013)doi 101016jcosust201311001

7 G M Mace et al Approaches to defining a planetary boundaryfor biodiversity Glob Environ Change 28 289ndash297 (2014)doi 101016jgloenvcha201407009

8 V Galaz Global Environmental Governance Technology andPolitics The Anthropocene Gap (Edward Elgar CheltenhamUK 2014)

9 UN GSP (UN High-Level Panel on Global Sustainability)Resilient People Resilient Planet A Future Worth Choosing(Report for the 2012 Rio+20 Earth Summit United NationsNew York 2012)

10 WBCSD (World Business Council on Sustainable Development)Action 2020 Overview (WBCSD Geneva Switzerlandhttpaction2020org accessed 18 June 2014)

11 R Costanza L Graumlich W Steffen Eds Integrated Historyand Future of People on Earth (MIT Press CambridgeMA USA 2006)

12 S Soumlrlin P Warde in Naturersquos End History and theEnvironment S Soumlrlin P Warde Eds (Palgrave MacMillanLondon 2009) pp 1ndash19

13 R C Bishop Endangered species and uncertainty Theeconomics of a safe minimum standard Am J Agric Econ 6110ndash18 (1978) doi 1023071240156

14 T M Crowards Safe minimum standards Costs andopportunities Ecol Econ 25 303ndash314 (1998) doi 101016S0921-8009(97)00041-4

15 W Steffen J Crutzen J R McNeill The Anthropocene Arehumans now overwhelming the great forces of NatureAmbio 36 614ndash621 (2007) doi 1015790044-7447(2007)36[614TAAHNO]20CO2 pmid 18240674

16 W Steffen et al Global Change and the Earth System A PlanetUnder Pressure (The IGBP Book Series Springer-VerlagBerlin Heidelberg New York 2004)

17 IPCC (Intergovernmental Panel on Climate Change) Managingthe risks of extreme events and disasters to advanceclimate change adaptation A special report of Working GroupsI and II of the IPCC CB Field et al Eds (CambridgeUniversity Press Cambridge UK (2012) doi 101017CBO9781139177245

18 IPCC (Intergovernmental Panel on Climate Change) ClimateChange 2013 The Physical Science Basis Summary forPolicymakers L Alexander et al Eds (IPCC SecretariatGeneva Switzerland 2013) doi 101017CBO9781107415324

19 P J Crutzen Geology of mankind Nature 415 23 (2002)doi 101038415023a pmid 11780095

20 K Richardson W Steffen D Liverman Climate Change GlobalRisks Challenges and Decisions (Cambridge Univ PressCambridge UK 2011)

21 T M Lenton et al Tipping elements in the Earthrsquos climatesystem Proc Natl Acad Sci USA 105 1786ndash1793 (2008)doi 101073pnas0705414105 pmid 18258748

22 M Scheffer et al Early-warning signals for criticaltransitions Nature 461 53ndash59 (2009) doi 101038nature08227 pmid 19727193

23 S R Carpenter W A Brock Rising variance A leadingindicator of ecological transition Ecol Lett 9 311ndash318 (2006)doi 101111j1461-0248200500877x pmid 16958897

24 J Bakke et al Rapid oceanic and atmospheric changes duringthe Younger Dryas cold period Nat Geosci 2 202ndash205(2009) doi 101038ngeo439

25 M Scheffer et al Anticipating critical transitions Science338 344ndash348 (2012) doi 101126science1225244pmid 23087241

26 R Wang et al Flickering gives early warning signals of acritical transition to a eutrophic lake state Nature 492419ndash422 (2012) doi 101038nature11655 pmid 23160492

27 R Biggs S R Carpenter W A Brock Turning back fromthe brink Detecting an impending regime shift in time to avertit Proc Natl Acad Sci USA 106 826ndash831 (2009)doi 101073pnas0811729106 pmid 19124774

28 M MacLeod et al Identifying chemicals that are planetaryboundary threats Environ Sci Technol 48 11057ndash11063(2014) doi 101021es501893m pmid 25181298

29 C S Holling Resilience and stability of ecological systemsAnnu Rev Ecol Syst 4 1ndash23 (1973) doi 101146annureves04110173000245

30 C Folke et al Resilience thinking Integrating resilienceadaptability and transformability Ecol Soc 15 20 (2010)wwwecologyandsocietyorgvol15iss4art20

31 T P Hughes S Carpenter J Rockstroumlm M SchefferB Walker Multiscale regime shifts and planetary boundariesTrends Ecol Evol 28 389ndash395 (2013) doi 101016jtree201305019 pmid 23769417

32 T M Lenton H T P Williams On the origin of planetary-scaletipping points Trends Ecol Evol 28 380ndash382 (2013)doi 101016jtree201306001 pmid 23777818

33 Supplementary text figures and tables are available onScience Online

34 NOAA (National Oceanic and Atmospheric Administration)NOAA-ESRL Annual CO2 Data accessed at httpco2noworgCurrent-CO2CO2-Nowannual-co2html (2014)

35 S E Perkins L V Alexander J Nairn Increasing frequencyintensity and duration of observed global heat waves and warmspells Geophys Res Lett 39 L20714 (2012) doi 1010292012GL053361

36 A Shepherd et al A reconciled estimate of ice-sheet massbalance Science 338 1183ndash1189 (2012) doi 101126science1228102 pmid 23197528

37 M R Helmus T J Bland C K Williams A R IvesPhylogenetic measures of biodiversity Am Nat 169 E68ndashE83(2007) doi 101086511334 pmid 17230400

38 S Drsquoagata et al Human-mediated loss of phylogeneticand functional diversity in coral reef fishes Curr Biol24 555ndash560 (2014) doi 101016jcub201401049pmid 24560574

39 A D Barnosky et al Has the Earthrsquos sixth mass extinctionalready arrived Nature 471 51ndash57 (2011) doi 101038nature09678 pmid 21368823

40 N W Mason F de Bello D Mouillot S Pavoine S Dray Aguide for using functional diversity indices to reveal changesin assembly processes along ecological gradients J VegSci 24 794ndash806 (2013) doi 101111jvs12013

41 R J Scholes R Biggs A biodiversity intactness index Nature434 45ndash49 (2005) doi 101038nature03289pmid 15744293

42 B Cardinale Ecology Impacts of biodiversity loss Science336 552ndash553 (2012) doi 101126science1222102pmid 22556243

43 D U Hooper et al A global synthesis reveals biodiversityloss as a major driver of ecosystem change Nature 486105ndash108 (2012) doi 101038nature11118pmid 22678289

44 BAS (British Antarctic Survey) ldquoAntarctic ozonerdquo wwwantarcticaacukmetjdsozoneindexhtmldata J ShanklinBritish Antarctic Survey (2013)

45 Royal Society Ocean Acidification Due to IncreasingAtmospheric Carbon Dioxide Policy Document 1205 (TheRoyal Society London 2005)

46 J M Guinotte V J Fabry Ocean acidification and its potentialeffects on marine ecosystems Ann N Y Acad Sci 1134320ndash342 (2008) doi 101196annals1439013pmid 18566099

47 D J Conley Terrestrial ecosystems and the globalbiogeochemical silica cycle Global Biogeochem Cycles 16681ndash688 (2002) doi 1010292002GB001894

SCIENCE sciencemagorg 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 1259855-9

RESEARCH | RESEARCH ARTICLE

48 F Vandevenne E Struyf W Clymans P Meire Agriculturalsilica harvest Have humans created a new loop in the globalsilica cycle Front Ecol Environ 10 243ndash248 (2012)doi 101890110046

49 S E Gress T D Nichols C C Northcraft W T PeterjohnNutrient limitation in soils exhibiting differing nitrogenavailabilities What lies beyond nitrogen saturation Ecol 88119ndash130 (2007) doi 1018900012-9658(2007)88[119NLISED]20CO2 pmid 17489460

50 H Hillebrand V Lehmpfuhl Resource stoichiometry andconsumers control the biodiversity-productivity relationship inpelagic metacommunities Am Nat 178 171ndash181 (2011)doi 101086660831 pmid 21750381

51 C M Moore et al Processes and patterns of oceanic nutrientlimitation Nat Geosci 6 701ndash710 (2013) doi 101038ngeo1765

52 G K MacDonald E M Bennett P A Potter N RamankuttyAgronomic phosphorus imbalances across the worldrsquoscroplands Proc Natl Acad Sci USA 108 3086ndash3091 (2011)doi 101073pnas1010808108 pmid 21282605

53 L Bouwman et al Exploring global changes in nitrogen andphosphorus cycles in agriculture induced by livestockproduction over the 1900-2050 period Proc Natl AcadSci USA 110 20882ndash20887 (2013) doi 101073pnas1012878108 pmid 21576477

54 W Steffen M Stafford Smith Planetary boundaries equityand global sustainability Why wealthy countries could benefitfrom more equity Curr Opinion Environ Sust 5 403ndash408(2013) doi 101016jcosust201304007

55 D J Greenwood et al A unifying concept for the dependenceof whole-crop N P ratio on biomass theory and experimentAnn Bot (Lond) 102 967ndash977 (2008) doi 101093aobmcn188 pmid 18840873

56 P K Snyder C Delire J A Foley Evaluating the influence ofdifferent vegetation biomes on the global climate Clim Dyn23 279ndash302 (2004) doi 101007s00382-004-0430-0

57 P C West G T Narisma C C Barford C J KucharikJ A Foley An alternative approach for quantifying climateregulation by ecosystems Front Ecol Environ 9 126ndash133(2010) doi 101890090015

58 EPI (Earth Policy Institute) ldquoForest coverrdquo wwwearthpolicyorgindicatorsC56forests_2012_ (2014)

59 M Falkenmark Meeting water requirements of an expandingworld population Philos Trans R Soc Lond B Biol Sci 352929ndash936 (1997) doi 101098rstb19970072

60 J S Wallace M C Acreman C A Sullivan The sharing ofwater between society and ecosystems From conflict tocatchment-based co-management Philos Trans R Soc LondB Biol Sci 358 2011ndash2026 (2003) doi 101098rstb20031383 pmid 14728795

61 N L Poff et al The natural flow regime A paradigm for riverconservation and restoration BioSci 47 769ndash784 (1997)doi 1023071313099

62 N L Poff J K H Zimmerman Ecological responses to alteredflow regimes A literature review to inform the science andmanagement of environmental flows Biol 55 194ndash205 (2010)doi 101111j1365-2427200902272x

63 A V Pastor F Ludwig H Biemans H Hoff P KabatAccounting for environmental flow requirements in globalwater assessments Hydrol Earth Syst Sci 18 5041ndash5059(2014) doi 105194hess-18-5041-2014

64 WHO (World Health Organization) Burden of Disease from theJoint Effects of Household and Ambient Air Pollution for 2012(wwwwhointphehealth_topicsoutdoorairdatabasesFINAL_HAP_AAP_BoD24March2014pdf accessed 23 June 2014httpwwwwhointphehealth_topicsoutdoorairdatabasesen)

65 O Boucher et al in Climate Change 2013 The Physical ScienceBasis IPCC AR5 WGI report T Stocker et al Eds (CambridgeUniv Press Cambridge UK 2013) chap 7 pp 571ndash657

66 M Chin et al Multi-decadal aerosol variations from 1980 to2009 A perspective from observations and a global modelAtmos Chem Phys 14 3657ndash3690 (2014) doi 105194acp-14-3657-2014

67 V Ramanathan et al Atmospheric brown clouds Impacts onSouth Asian climate and hydrological cycle Proc Natl AcadSci USA 102 5326ndash5333 (2005) doi 101073pnas0500656102 pmid 15749818

68 M Cole P Lindeque C Halsband T S Galloway Microplasticsas contaminants in the marine environment A review MarPollut Bull 62 2588ndash2597 (2011) doi 101016jmarpolbul201109025 pmid 22001295

69 EEA (European Environment Agency) Genetically ModifiedOrganisms (GMOs) The Significance of Gene Flow ThroughPollen Transfer (Environmental Issue Report 28 EuropeanEnvironment Agency Copenhagen Denmark 2002)

70 J A Ivar do Sul M F Costa The present and future ofmicroplastic pollution in the marine environment Environ Pollut185 352ndash364 (2014) doi 101016jenvpol201310036pmid 24275078

71 R Kessler Engineered nanoparticles in consumer productsUnderstanding a new ingredient Environ Health Perspect 119a120ndasha125 (2011) doi 101289ehp119-a120 pmid 21356630

72 M Rees Our Final Century Will Civilisation Survive theTwenty-first Century (Arrow Books London 2003)

73 L M Persson et al Confronting unknown planetary boundarythreats from chemical pollution Environ Sci Technol 4712619ndash12622 (2013) doi 101021es402501c pmid 23980998

74 P P Egeghy et al The exposure data landscape formanufactured chemicals Sci Total Environ 414 159ndash166(2012) doi 101016jscitotenv201110046 pmid 22104386

75 UNEP (United Nations Environment Programme) GCOGlobal Chemicals Outlook Towards Sound Management ofChemicals (United Nations Environment ProgrammeNairobi Kenya 2013)

76 S Strempel M Scheringer C A Ng K HungerbuumlhlerScreening for PBT chemicals among the ldquoexistingrdquo andldquonewrdquo chemicals of the EU Environ Sci Technol 465680ndash5687 (2012) doi 101021es3002713pmid 22494215

77 M Scheringer et al How many persistent organic pollutantsshould we expect Atmos Poll Res 3 383ndash391 (2012)doi 105094APR2012044

78 K Sanderson Chemistry Itrsquos not easy being green Nature469 18ndash20 (2011) doi 101038469018a pmid 21209638

79 P A Schulte et al Occupational safety and health greenchemistry and sustainability A review of areas ofconvergence Environ Health 12 31 (2013) doi 1011861476-069X-12-31 pmid 23587312

80 EEA (European Environment Agency) Late Lessons from EarlyWarnings The Precautionary Principle 1896-2000 (EnvironmentalIssue Report 222001 Copenhagen Denmark 2001)

81 D Gee Late lessons from early warnings Toward realism andprecaution with endocrine-disrupting substances EnvironHealth Perspect 114 (suppl 1) 152ndash160 (2006) doi 101289ehp8134 pmid 16818262

82 T Lenton A Watson A Revolutions That Made the Earth(Oxford Univ Press Oxford UK 2011)

83 R Biggs et al Toward principles for enhancing the resilienceof ecosystem services Annu Rev Environ Resour 37421ndash448 (2012) doi 101146annurev-environ-051211-123836

84 G S Cumming P Olsson F S Chapin III C S HollingResilience experimentation and scale mismatches in social-ecological systems Landscape Ecol 28 1139ndash1150 (2013)doi 101007s10980-012-9725-4

85 D Griggs et al Policy Sustainable development goals forpeople and planet Nature 495 305ndash307 (2013) doi 101038495305a pmid 23518546

86 R Costanza Ed Ecological Economics The Science andManagement of Sustainability (Columbia Univ PressNew York 1991)

87 C Folke in Linking the Natural Environment and the EconomyEssays from the Eco-Eco Group C Folke T Karingberger Eds(Kluwer Academic Publishers Dordrecht Netherlands 1991)pp 77ndash94

88 L Robin S Soumlrlin P Warde Eds The Future of NatureDocuments of Global Change (Yale Univ Press New Haven CT2013)

89 U Heise Sense of Place and Sense of Planet TheEnvironmental Imagination of the Global (Oxford Univ PressOxford 2008)

90 M Scheffer Critical Transitions in Nature and Society(Princeton Univ Press Princeton NJ 2009)

91 J Masco Bad weather On planetary crisis Soc Stud Sci 407ndash40 (2010) doi 1011770306312709341598

92 G Paacutelsson et al Reconceptualizing the lsquoAnthroposrsquo in theAnthropocene Integrating the social sciences and humanitiesin global environmental change research Environ Sci Policy28 4 (2013) doi 101016jenvsci201211004

93 N Castree et al Changing the intellectual climate NatureClim Change 4 763ndash768 (2014) doi 101038nclimate2339

94 J M Anderies S R Carpenter W Steffen J Rockstroumlm Thetopology of non-linear global carbon dynamics From tippingpoints to planetary boundaries Environ Res Lett 8 044048(2013) doi 1010881748-932684044048

95 S E Cornell I C Prentice J I House C J DownyUnderstanding the Earth System Global Change Science forApplication (Cambridge Univ Press Cambridge 2012)

96 J A Dearing et al Safe and just operating spaces for regionalsocial-ecological systems Glob Environ Change 28 227ndash238(2014) doi 101016jgloenvcha201406012

ACKNOWLEDGMENTS

We thank J Foley and N Ramunkutty for contributions to theland-system change boundary A Pastor for analytical work on thePB for freshwater B Armstrong C Butler T McMichael andA Woodward for contributions to the novel entities boundary andB Scholes for comments on an earlier version of the manuscriptData associated with the paper are located at the StockholmResilience Centre Sweden (httpwwwstockholmresilienceorg21researchresearch-programmesplanetary-boundarieshtml)The planetary boundaries research at the Stockholm ResilienceCentre is made possible through a core grant from MISTRA(Swedish Foundation for Strategic Environmental Research) SECis supported by the Swedish Research Council EMB is supportedby the Natural Sciences and Engineering Research Council ofCanada and by the Trottier Institute for Science and Public PolicyRB is supported by a Branco Weiss Fellowship CF is supportedby the Family Erling Persson Academy Programme on GlobalEconomic Dynamics and the Biosphere IF is supported by theStordalen Foundation (Norway) SS is supported by theRiksbanken Jubileumsfond and the Institute for Advanced StudyPrinceton NJ and SRC and VR are supported bythe US National Science Foundation

SUPPLEMENTARY MATERIALS

wwwsciencemagorgcontent34762231259855supplDC1MethodsFigs S1 to S10Tables S1 to S3References (97ndash158)

11 August 2014 accepted 8 January 2015Published online 15 January 2015101126science1259855

1259855-10 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 sciencemagorg SCIENCE

RESEARCH | RESEARCH ARTICLE

DOI 101126science1259855 (2015)347 Science

et alWill SteffenplanetPlanetary boundaries Guiding human development on a changing

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clicking herecolleagues clients or customers by you can order high-quality copies for yourIf you wish to distribute this article to others

herefollowing the guidelines

can be obtained byPermission to republish or repurpose articles or portions of articles

) February 12 2015 wwwsciencemagorg (this information is current as of

The following resources related to this article are available online at

httpwwwsciencemagorgcontent34762231259855fullhtmlversion of this article at

including high-resolution figures can be found in the onlineUpdated information and services

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can berelated to this article A list of selected additional articles on the Science Web sites

httpwwwsciencemagorgcontent34762231259855fullhtmlref-list-1 27 of which can be accessed freecites 120 articlesThis article

httpwwwsciencemagorgcgicollectionecologyEcology

subject collectionsThis article appears in the following

registered trademark of AAAS is aScience2015 by the American Association for the Advancement of Science all rights reserved The title

CopyrightAmerican Association for the Advancement of Science 1200 New York Avenue NW Washington DC 20005 (print ISSN 0036-8075 online ISSN 1095-9203) is published weekly except the last week in December by theScience

on

Feb

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from

where it is currently in excess to areas where thesoil is naturally P-poormay simultaneously boostglobal crop production and reduce the transgres-sion of the regional-level P boundary (3 52 54)The N boundary has been taken from the com-

prehensive analysis of de Vries et al (5) whichproposed a PB for eutrophication of aquatic eco-systems of 62 Tg N yearndash1 from industrial andintentional biological N fixation using the moststringent water quality criterion As for the Pboundary a few agricultural regions of very highN application rates are the main contributors tothe transgression of this boundary (Fig 2 andfig S5B) This suggests that a redistribution of Ncould simultaneously boost global crop produc-tion and reduce the transgression of the regional-level boundaryBecause the major anthropogenic perturba-

tion of both the N and P cycles arises from fertil-izer application we can analyze the links betweenthe independently determined N and P bounda-ries in an integrated way based on the NP ratioin the growing plant tissue of agricultural cropsApplying this ratio which is on average 118 (55)to the P boundary (62 Tg P yearndash1) gives an Nboundary of 73 Tg N yearndash1 Conversely applyingthe ratio to theN boundary (62 TgN yearndash1) givesa P boundary of 53 Tg P yearndash1 The small dif-ferences between the boundaries derived usingthe NP ratio and those calculated independent-ly which are likely nonsignificant differencesgiven the precision of the data available for thecalculations show the internal consistency inour approach to the biogeochemical boundariesMore detail on the development of the P andN

boundaries is given in (33) where we also em-phasize that the proposed P and N boundariesmay be larger for an optimal allocation of N (andP) over the globe

Land-system change

The updated biosphere integrity boundary pro-vides a considerable constraint on the amountand pattern of land-system change in all ter-restrial biomes forests woodlands savannasgrasslands shrublands tundra and so on Theland-system change boundary is now focusedmore tightly on a specific constraint the biogeo-physical processes in land systems that directlyregulate climatemdashexchange of energy water andmomentum between the land surface and theatmosphere The control variable has been changedfrom the amount of cropland to the amount offorest cover remaining as the three major forestbiomesmdashtropical temperate and borealmdashplay astronger role in land surfacendashclimate couplingthan other biomes (56 57) In particular we fo-cus on those land-system changes that can in-fluence the climate in regions beyond the regionwhere the land-system change occurredOf the forest biomes tropical forests have sub-

stantial feedbacks to climate through changes inevapotranspiration when they are converted tononforested systems and changes in the distribu-tion of boreal forests affect the albedo of the landsurface and hence regional energy exchange Bothhave strong regional and global teleconnections

The biome-level boundary for these two types offorest have been set at 85 (Table 1 and thesupplementary materials) and the boundary fortemperate forests has been proposed at 50 ofpotential forest cover because changes to tem-perate forests are estimated to have weaker in-fluences on the climate system at the global levelthan changes to the other two major forestbiomes (56) These boundaries would almostsurely be met if the proposed biosphere integ-rity boundary of 90 BII were respectedEstimates of the current status of the land-

system change boundary are given in Figs 2 and3 and fig S6 and in (58)

Freshwater use

The revised freshwater use boundary has retainedconsumptive use of blue water [from rivers lakesreservoirs and renewable groundwater stores(59)] as the global-level control variable and4000 km3year as the value of the boundaryThis PB may be somewhat higher or lower de-pending on riversrsquo ecological flow requirements(6) Therefore we report here a new assessmentto complement the PB with a basin-scale bound-ary for the maximum rate of blue water with-drawal along rivers based on the amount of waterrequired in the river system to avoid regime shiftsin the functioning of flow-dependent ecosystemsWe base our control variable on the concept ofenvironmental water flows (EWF) which definesthe level of river flows for different hydrologicalcharacteristics of river basins adequate to main-tain a fair-to-good ecosystem state (60ndash62)The variable monthly flow (VMF) method

(33 63) was used to calculate the basin-scaleboundary for water This method takes accountof intra-annual variability by classifying flow re-gimes into high- intermediate- and low-flowmonths and allocating EWF as a percentage ofthe mean monthly flow (MMF) Based on thisanalysis the zones of uncertainty for the river-basin scale water boundary were set at 25 to 55of MMF for the low-flow regime 40 to 70 forthe intermediate-flow regime and 55 to 85 forthe high-flow regime (table S2) The boundarieswere set at the lower end of the uncertaintyranges that encompass average monthly EWFOur new estimates of the current status of thewater use boundarymdashcomputed based on gridcellndashspecific estimates of agricultural industrialand domestic water withdrawalsmdashare shown inFigs 2 and 3 with details in figs S7 and S8

Atmospheric aerosol loading

Aerosols have well-known serious human healtheffects leading to about 72 million deaths peryear (64) They also affect the functioning of theEarth system in many ways (65) (fig S9) Herewe focus on the effect of aerosols on regionalocean-atmosphere circulation as the rationalefor a separate aerosols boundary We adopt aero-sol optical depth (AOD) (33) as the control var-iable and use the south Asian monsoon as a casestudy based on the potential of widespread aero-sol loading over the Indian subcontinent to switchthe monsoon system to a drier state

The background AOD over south Asia is ~015and can be as high as 04 during volcanic events(66) Emissions of black carbon and organic car-bon from cooking and heating with biofuels andfrom diesel transportation and emission of sul-fates and nitrates from fossil fuel combustioncan increase seasonal mean AODs to as high as04 (larger during volcanic periods) leading todecreases of 10 to 15 of incident solar radiationat the surface (fig S9) A substantial decrease inmonsoon activity is likely around an AOD of 050an increase of 035 above the background (67)Taking a precautionary approach toward uncer-tainties surrounding the position of the tippingpoint we propose a boundary at an AOD of 025(an increase due to human activities of 01) witha zone of uncertainty of 025 to 050 The annualmean AOD is currently about 03 (66) within thezone of uncertainty

Introduction of novel entities

We define novel entities as new substances newforms of existing substances and modified lifeforms that have the potential for unwanted geo-physical andor biological effects Anthropogenicintroduction of novel entities to the environmentis of concern at the global level when these en-tities exhibit (i) persistence (ii) mobility acrossscales with consequent widespread distributionsand (iii) potential impacts on vital Earth-systemprocesses or subsystems These potentially in-clude chemicals and other new types of engi-neered materials or organisms [eg (68ndash71)] notpreviously known to the Earth system as well asnaturally occurring elements (for example heavymetals) mobilized by anthropogenic activitiesThe risks associated with the introduction ofnovel entities into the Earth system are exempli-fied by the release of CFCs (chlorofluorocarbons)which are very useful synthetic chemicals thatwere thought to be harmless but had unexpecteddramatic impacts on the stratospheric ozone layerIn effect humanity is repeatedly running suchglobal-scale experiments but not yet applying theinsights from previous experience to new appli-cations (72 73)Today there aremore than 100000 substances

in global commerce (74) If nanomaterials andplastic polymers that degrade to microplasticsare included the list is even longer There is alsoa ldquochemical intensificationrdquo due to the rapidlyincreasing global production of chemicals theexpanding worldwide distribution as chemicalproducts or in consumer goods and the exten-sive global trade in chemical wastes (75)In recent years there has been a growing de-

bate about the global-scale effects of chemicalpollution leading to calls for the definition ofcriteria to identify the kinds of chemical sub-stances that are likely to be globally problematic(76 77) Persson et al (73) proposed that there arethree conditions that need to be fulfilled for achemical to pose a threat to the Earth system (i)the chemical has an unknown disruptive effecton a vital Earth-systemprocess (ii) the disruptiveeffect is not discovered until it is a problem at theglobal scale and (iii) the effect is not readily

SCIENCE sciencemagorg 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 1259855-7

RESEARCH | RESEARCH ARTICLE

reversible The challenge to the research commu-nity is to develop the knowledge base that allowsthe screening of chemicals before they are re-leased into the environment for properties thatmay predispose them toward becoming globalproblemsAs a first step toward meeting this challenge

the three conditions outlined above have beenused as the basis for identifying scenarios ofchemical pollution that fulfill the conditions andas a next step for pinpointing chemical profilesthat fit the scenarios (28) This proposal consti-tutes a first attempt at adding the Earth-systemperspective when assessing hazard and risk ofchemicals and offers a vision for a systematic ap-proach to a complex management situation withmany unknownsDespite this progress in developing an Earth-

systemndashoriented approach there is not yet anaggregate global-level analysis of chemical pol-lution on which to base a control variable or aboundary value It may also serve little purposeto define boundary values and control varia-bles for a planetary boundary of this complexityNevertheless there is a potential threat fromnovel entities to disrupt the functioning of theEarth-system and society needs to learn how tomitigate these unknown risks and manage chem-icals under uncertainty (28 73)Some precautionary and preventive actions

can be considered These may include a strongerfocus on green chemistry (78) finding synergieswith risk-reducing interventions in other fieldssuch as occupational health (79) paying moreattention to learning from earlier mistakes (8081) and investing in science to better under-stand and monitor vital Earth-system processesin order to be able to detect disruptive effectsfrom novel entities as early as possible

Hierarchy of boundaries

An analysis of the many interactions among theboundaries (table S3 and fig S10) suggests thattwo of themmdashclimate change and biosphereintegritymdashare highly integrated emergent system-level phenomena that are connected to all of theother PBs They operate at the level of the wholeEarth system (7) and have coevolved for nearly4 billion years (82) They are regulated by theother boundaries and on the other hand pro-vide the planetary-level overarching systems with-in which the other boundary processes operateFurthermore large changes in the climate or inbiosphere integrity would likely on their ownpush the Earth system out of the Holocene stateIn fact transitions between time periods in Earthhistory have often been delineated by substantialshifts in climate the biosphere or both (82 83)These observations suggest a two-level hierar-

chy of boundaries in which climate change andbiosphere integrity should be recognized as coreplanetary boundaries through which the otherboundaries operate The crossing of one or moreof the other boundaries may seriously affect hu-man well-being and may predispose the trans-gression of a core boundary(ies) but does not byitself lead to a new state of the Earth system This

hierarchical approach to classifying the bounda-ries becomes clearer by examining inmore detailthe roles of climate and biosphere integrity in thefunctioning of the Earth systemThe climate system is a manifestation of the

amount distribution and net balance of energyat Earthrsquos surface The total amount of energysets the overall conditions for life In Earthrsquos cur-rent climate a range of global surface temper-atures and atmospheric pressures allows the threephases of water to be present simultaneouslywith ice and water vapor playing critical roles inthe physical feedbacks of the climate system Thedistribution of energy by latitude over the landand sea surfaces and within the ocean plays amajor role in the circulation of the two greatfluids the ocean and the atmosphere These sys-temic physical characteristics are key spatial de-terminants of the distribution of the biota andthe structure and functioning of ecosystems andare controllers of biogeochemical flowsBiosphere integrity is also crucial to Earth-

system functioning where the biosphere is de-fined as the totality of all ecosystems (terrestrialfreshwater andmarine) on Earth and their biota(32) These ecosystems and biota play a criticalrole in determining the state of the Earth systemregulating its material and energy flows and itsresponses to abrupt and gradual change (7) Di-versity in the biosphere provides resilience toterrestrial and marine ecosystems (83 84) Thebiosphere not only interacts with the other plan-etary boundaries but also increases the capacityof theEarth system topersist in a given state underchanges in these other boundaries The ultimatebasis for the many roles that the biosphere playsin Earth-system dynamics is the genetic code ofthe biota the basic information bank that de-fines the biospherersquos functional role and its ca-pacity to innovate and persist into the future

Planetary boundaries in asocietal context

A proposed approach for sustainable develop-ment goals (SDGs) (85) argues that the stablefunctioning of the Earth system is a prereq-uisite for thriving societies around the world Thisapproach implies that the PB framework orsomething like it will need to be implementedalongside the achievement of targets aimed atmore immediate human needs such as provi-sion of clean affordable and accessible energyand the adequate supply of food World devel-opment within the biophysical limits of a stableEarth system has always been a necessity [eg(86 87)] However only recently for a numberof reasons has it become possible to identifyevaluate and quantify risks of abrupt planetary-and biome-level shifts due to overshoot of keyEarth-system parameters (i) the emergence ofglobal-change thinking and Earth-system think-ing (88) (ii) the rise of ldquothe Planetaryrdquo as a rel-evant level of complex system understanding(89ndash92) and (iii) observable effects of the rapidincrease in human pressures on the planet (16)The PB approach is embedded in this emerg-

ing social context but it does not suggest how to

maneuver within the safe operating space in thequest for global sustainability For example thePB framework does not as yet account for the re-gional distribution of the impact or its histor-ical patterns Nor does the PB framework takeinto account the deeper issues of equity and cau-sation The current levels of the boundary pro-cesses and the transgressions of boundaries thathave already occurred are unevenly caused bydifferent human societies and different socialgroups The wealth benefits that these trans-gressions have brought are also unevenly distrib-uted socially and geographically It is easy toforesee that uneven distribution of causation andbenefits will continue and these differentialsmust surely be addressed for a Holocene-likeEarth-system state to be successfully legitimatedand maintained However the PB framework ascurrently construed provides no guidance as tohow this may be achieved [although some po-tential synergies have been noted (54)] and itcannot readily be used tomake choices betweenpathways for piecemeal maneuvering withinthe safe operating space ormore radical shifts ofglobal governance (93)The nature of the PB framework implies that

two important cautions should be observedwhenapplication of the framework to policy or man-agement is proposed boundary interactions andscale

Boundary interactions

The planetary boundaries framework arises fromthe scientific evidence that Earth is a singlecomplex integrated systemmdashthat is the bound-aries operate as an interdependent set [eg(94)] (table S1 and fig S10) Although a system-atic quantitative analysis of interactions amongall of the processes for which boundaries areproposed remains beyond the scope of currentmodeling and observational capacity the Earthsystem clearly operates in well-defined states inwhich these processes and their interactionscan create stabilizing or destabilizing feedbacks(16 90 95) This has profound implications forglobal sustainability because it emphasizes theneed to address multiple interacting environ-mental processes simultaneously (eg stabilizingthe climate system requires sustainable forestmanagement and stable ocean ecosystems)

Scale

The PB framework is not designed to be ldquodown-scaledrdquo or ldquodisaggregatedrdquo to smaller levels suchas nations or local communities That said thePB framework recognizes the importance ofchanges at the level of subsystems in the Earthsystem (eg biomes or large river basins) on thefunctioning of the Earth system as a whole Alsothere are strong arguments for an integrated ap-proach coupling boundary definitions at region-al and global levels with development goals toenable the application of ldquoPB thinkingrdquo at lev-els (nations basins and regions) where policyaction most commonly occurs [eg (85 96)]This update of the PB framework is one step on

a longer-term evolution of scientific knowledge to

1259855-8 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 sciencemagorg SCIENCE

RESEARCH | RESEARCH ARTICLE

inform and support global sustainability goalsand pathways This evolution is needed morethan ever before there are severe implementa-tion gaps inmany global environmental policiesrelating to the PB issues where problematictrends are not being halted or reversed despiteinternational consensus about the urgency of theproblems The prospect of tighter resource con-straints and rising environmental hazards is alsounavoidably turning the focus onto global socialequity and the planetary stewardship of Earthrsquoslife-support system There is a need for a trulyglobal evidence base with much greater integra-tion among issues in order to respond to theseglobal challenges New research initiatives [egFuture Earth (wwwfutureearthorg)] provide evi-dence that science can respond to this need byapplying Earth-system research to advance a newgeneration of integrated global analyses and toexplore options for transformations toward sus-tainability This is a clear sign that as the risksof the Anthropocene to human well-being be-come clearer research is maturing to a pointwhere a systemic step-change is possiblemdashandnecessarymdashin exploring and defining a safe andjust planetary operating space for the furtherdevelopment of human societies

Methods summary

Our approach to building the planetary bound-aries framework is described above We haveimplemented the framework through an ex-pert assessment and synthesis of the scientificknowledge of intrinsic biophysical processes thatregulate the stability of the Earth system Ourprecautionary approach is based on the main-tenance of a Holocene-like state of the Earthsystem and on an assessment of the level ofhuman-driven change that would risk destabi-lizing this state For the climate change PB thereis already much literature on which to basesuch an assessment For others such as strato-spheric ozone ocean acidification extinctionrates and P andN cycles we have used estimatesof preindustrial values of the control variableas a Holocene baseline Where large undesira-ble thresholds exist and have been studied (egpolar ice sheets Amazon rainforest aragonitedissolution atmospheric aerosols and the southAsian monsoon) quantitative boundaries can bereadily proposed For others where the focus ison erosion of Earth-system resilience the bound-aries are more difficult (but not impossible) toquantify as reflected in larger uncertainty zonesWe used large-scale assessments of the impacts

of human activities on Earth-system functioning[eg Intergovernmental Panel on Climate Change(17 18) the International Geosphere-BiosphereProgramme synthesis (16) and chemicals (75 80)]as sources of community-level understandingon which to propose PBs Our update has alsorelied on post-2009 assessments of individualboundaries by the relevant expert research com-munities examples include phosphorus (3) ni-trogen (5) biosphere integrity (7) freshwater use(5 63) and novel entities [with a focus on chem-icals (28 73)] Finally some new analyses have

been undertaken specifically for this paper (i) afreshwater-use PB based on the EWF approach(33 63) (ii) the linkage of the phosphorus andnitrogen boundaries via the NP ratio in grow-ing crop tissue (33) and (iii) the use of majorforest biomes as the basis for the land-systemchange PB (33)

REFERENCES AND NOTES

1 J Rockstroumlm et al Planetary boundaries Exploring the safeoperating space for humanity Ecol Soc 14 32 (2009)httpwwwecologyandsocietyorgvol14iss2art32

2 J Rockstroumlm et al A safe operating space for humanityNature 461 472ndash475 (2009) doi 101038461472apmid 19779433

3 S R Carpenter E M Bennett Reconsideration of theplanetary boundary for phosphorus Environ Res Lett 6014009 (2011) doi 1010881748-932661014009

4 S W Running Ecology A measurable planetary boundaryfor the biosphere Science 337 1458ndash1459 (2012)doi 101126science1227620 pmid 22997311

5 W de Vries J Kros C Kroeze S P Seitzinger Assessingplanetary and regional nitrogen boundaries related to foodsecurity and adverse environmental impacts Curr OpinionEnviron Sust 5 392ndash402 (2013) doi 101016jcosust201307004

6 D Gerten et al Towards a revised planetary boundary forconsumptive freshwater use Role of environmental flowrequirements Curr Opinion Environ Sust 5 551ndash558 (2013)doi 101016jcosust201311001

7 G M Mace et al Approaches to defining a planetary boundaryfor biodiversity Glob Environ Change 28 289ndash297 (2014)doi 101016jgloenvcha201407009

8 V Galaz Global Environmental Governance Technology andPolitics The Anthropocene Gap (Edward Elgar CheltenhamUK 2014)

9 UN GSP (UN High-Level Panel on Global Sustainability)Resilient People Resilient Planet A Future Worth Choosing(Report for the 2012 Rio+20 Earth Summit United NationsNew York 2012)

10 WBCSD (World Business Council on Sustainable Development)Action 2020 Overview (WBCSD Geneva Switzerlandhttpaction2020org accessed 18 June 2014)

11 R Costanza L Graumlich W Steffen Eds Integrated Historyand Future of People on Earth (MIT Press CambridgeMA USA 2006)

12 S Soumlrlin P Warde in Naturersquos End History and theEnvironment S Soumlrlin P Warde Eds (Palgrave MacMillanLondon 2009) pp 1ndash19

13 R C Bishop Endangered species and uncertainty Theeconomics of a safe minimum standard Am J Agric Econ 6110ndash18 (1978) doi 1023071240156

14 T M Crowards Safe minimum standards Costs andopportunities Ecol Econ 25 303ndash314 (1998) doi 101016S0921-8009(97)00041-4

15 W Steffen J Crutzen J R McNeill The Anthropocene Arehumans now overwhelming the great forces of NatureAmbio 36 614ndash621 (2007) doi 1015790044-7447(2007)36[614TAAHNO]20CO2 pmid 18240674

16 W Steffen et al Global Change and the Earth System A PlanetUnder Pressure (The IGBP Book Series Springer-VerlagBerlin Heidelberg New York 2004)

17 IPCC (Intergovernmental Panel on Climate Change) Managingthe risks of extreme events and disasters to advanceclimate change adaptation A special report of Working GroupsI and II of the IPCC CB Field et al Eds (CambridgeUniversity Press Cambridge UK (2012) doi 101017CBO9781139177245

18 IPCC (Intergovernmental Panel on Climate Change) ClimateChange 2013 The Physical Science Basis Summary forPolicymakers L Alexander et al Eds (IPCC SecretariatGeneva Switzerland 2013) doi 101017CBO9781107415324

19 P J Crutzen Geology of mankind Nature 415 23 (2002)doi 101038415023a pmid 11780095

20 K Richardson W Steffen D Liverman Climate Change GlobalRisks Challenges and Decisions (Cambridge Univ PressCambridge UK 2011)

21 T M Lenton et al Tipping elements in the Earthrsquos climatesystem Proc Natl Acad Sci USA 105 1786ndash1793 (2008)doi 101073pnas0705414105 pmid 18258748

22 M Scheffer et al Early-warning signals for criticaltransitions Nature 461 53ndash59 (2009) doi 101038nature08227 pmid 19727193

23 S R Carpenter W A Brock Rising variance A leadingindicator of ecological transition Ecol Lett 9 311ndash318 (2006)doi 101111j1461-0248200500877x pmid 16958897

24 J Bakke et al Rapid oceanic and atmospheric changes duringthe Younger Dryas cold period Nat Geosci 2 202ndash205(2009) doi 101038ngeo439

25 M Scheffer et al Anticipating critical transitions Science338 344ndash348 (2012) doi 101126science1225244pmid 23087241

26 R Wang et al Flickering gives early warning signals of acritical transition to a eutrophic lake state Nature 492419ndash422 (2012) doi 101038nature11655 pmid 23160492

27 R Biggs S R Carpenter W A Brock Turning back fromthe brink Detecting an impending regime shift in time to avertit Proc Natl Acad Sci USA 106 826ndash831 (2009)doi 101073pnas0811729106 pmid 19124774

28 M MacLeod et al Identifying chemicals that are planetaryboundary threats Environ Sci Technol 48 11057ndash11063(2014) doi 101021es501893m pmid 25181298

29 C S Holling Resilience and stability of ecological systemsAnnu Rev Ecol Syst 4 1ndash23 (1973) doi 101146annureves04110173000245

30 C Folke et al Resilience thinking Integrating resilienceadaptability and transformability Ecol Soc 15 20 (2010)wwwecologyandsocietyorgvol15iss4art20

31 T P Hughes S Carpenter J Rockstroumlm M SchefferB Walker Multiscale regime shifts and planetary boundariesTrends Ecol Evol 28 389ndash395 (2013) doi 101016jtree201305019 pmid 23769417

32 T M Lenton H T P Williams On the origin of planetary-scaletipping points Trends Ecol Evol 28 380ndash382 (2013)doi 101016jtree201306001 pmid 23777818

33 Supplementary text figures and tables are available onScience Online

34 NOAA (National Oceanic and Atmospheric Administration)NOAA-ESRL Annual CO2 Data accessed at httpco2noworgCurrent-CO2CO2-Nowannual-co2html (2014)

35 S E Perkins L V Alexander J Nairn Increasing frequencyintensity and duration of observed global heat waves and warmspells Geophys Res Lett 39 L20714 (2012) doi 1010292012GL053361

36 A Shepherd et al A reconciled estimate of ice-sheet massbalance Science 338 1183ndash1189 (2012) doi 101126science1228102 pmid 23197528

37 M R Helmus T J Bland C K Williams A R IvesPhylogenetic measures of biodiversity Am Nat 169 E68ndashE83(2007) doi 101086511334 pmid 17230400

38 S Drsquoagata et al Human-mediated loss of phylogeneticand functional diversity in coral reef fishes Curr Biol24 555ndash560 (2014) doi 101016jcub201401049pmid 24560574

39 A D Barnosky et al Has the Earthrsquos sixth mass extinctionalready arrived Nature 471 51ndash57 (2011) doi 101038nature09678 pmid 21368823

40 N W Mason F de Bello D Mouillot S Pavoine S Dray Aguide for using functional diversity indices to reveal changesin assembly processes along ecological gradients J VegSci 24 794ndash806 (2013) doi 101111jvs12013

41 R J Scholes R Biggs A biodiversity intactness index Nature434 45ndash49 (2005) doi 101038nature03289pmid 15744293

42 B Cardinale Ecology Impacts of biodiversity loss Science336 552ndash553 (2012) doi 101126science1222102pmid 22556243

43 D U Hooper et al A global synthesis reveals biodiversityloss as a major driver of ecosystem change Nature 486105ndash108 (2012) doi 101038nature11118pmid 22678289

44 BAS (British Antarctic Survey) ldquoAntarctic ozonerdquo wwwantarcticaacukmetjdsozoneindexhtmldata J ShanklinBritish Antarctic Survey (2013)

45 Royal Society Ocean Acidification Due to IncreasingAtmospheric Carbon Dioxide Policy Document 1205 (TheRoyal Society London 2005)

46 J M Guinotte V J Fabry Ocean acidification and its potentialeffects on marine ecosystems Ann N Y Acad Sci 1134320ndash342 (2008) doi 101196annals1439013pmid 18566099

47 D J Conley Terrestrial ecosystems and the globalbiogeochemical silica cycle Global Biogeochem Cycles 16681ndash688 (2002) doi 1010292002GB001894

SCIENCE sciencemagorg 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 1259855-9

RESEARCH | RESEARCH ARTICLE

48 F Vandevenne E Struyf W Clymans P Meire Agriculturalsilica harvest Have humans created a new loop in the globalsilica cycle Front Ecol Environ 10 243ndash248 (2012)doi 101890110046

49 S E Gress T D Nichols C C Northcraft W T PeterjohnNutrient limitation in soils exhibiting differing nitrogenavailabilities What lies beyond nitrogen saturation Ecol 88119ndash130 (2007) doi 1018900012-9658(2007)88[119NLISED]20CO2 pmid 17489460

50 H Hillebrand V Lehmpfuhl Resource stoichiometry andconsumers control the biodiversity-productivity relationship inpelagic metacommunities Am Nat 178 171ndash181 (2011)doi 101086660831 pmid 21750381

51 C M Moore et al Processes and patterns of oceanic nutrientlimitation Nat Geosci 6 701ndash710 (2013) doi 101038ngeo1765

52 G K MacDonald E M Bennett P A Potter N RamankuttyAgronomic phosphorus imbalances across the worldrsquoscroplands Proc Natl Acad Sci USA 108 3086ndash3091 (2011)doi 101073pnas1010808108 pmid 21282605

53 L Bouwman et al Exploring global changes in nitrogen andphosphorus cycles in agriculture induced by livestockproduction over the 1900-2050 period Proc Natl AcadSci USA 110 20882ndash20887 (2013) doi 101073pnas1012878108 pmid 21576477

54 W Steffen M Stafford Smith Planetary boundaries equityand global sustainability Why wealthy countries could benefitfrom more equity Curr Opinion Environ Sust 5 403ndash408(2013) doi 101016jcosust201304007

55 D J Greenwood et al A unifying concept for the dependenceof whole-crop N P ratio on biomass theory and experimentAnn Bot (Lond) 102 967ndash977 (2008) doi 101093aobmcn188 pmid 18840873

56 P K Snyder C Delire J A Foley Evaluating the influence ofdifferent vegetation biomes on the global climate Clim Dyn23 279ndash302 (2004) doi 101007s00382-004-0430-0

57 P C West G T Narisma C C Barford C J KucharikJ A Foley An alternative approach for quantifying climateregulation by ecosystems Front Ecol Environ 9 126ndash133(2010) doi 101890090015

58 EPI (Earth Policy Institute) ldquoForest coverrdquo wwwearthpolicyorgindicatorsC56forests_2012_ (2014)

59 M Falkenmark Meeting water requirements of an expandingworld population Philos Trans R Soc Lond B Biol Sci 352929ndash936 (1997) doi 101098rstb19970072

60 J S Wallace M C Acreman C A Sullivan The sharing ofwater between society and ecosystems From conflict tocatchment-based co-management Philos Trans R Soc LondB Biol Sci 358 2011ndash2026 (2003) doi 101098rstb20031383 pmid 14728795

61 N L Poff et al The natural flow regime A paradigm for riverconservation and restoration BioSci 47 769ndash784 (1997)doi 1023071313099

62 N L Poff J K H Zimmerman Ecological responses to alteredflow regimes A literature review to inform the science andmanagement of environmental flows Biol 55 194ndash205 (2010)doi 101111j1365-2427200902272x

63 A V Pastor F Ludwig H Biemans H Hoff P KabatAccounting for environmental flow requirements in globalwater assessments Hydrol Earth Syst Sci 18 5041ndash5059(2014) doi 105194hess-18-5041-2014

64 WHO (World Health Organization) Burden of Disease from theJoint Effects of Household and Ambient Air Pollution for 2012(wwwwhointphehealth_topicsoutdoorairdatabasesFINAL_HAP_AAP_BoD24March2014pdf accessed 23 June 2014httpwwwwhointphehealth_topicsoutdoorairdatabasesen)

65 O Boucher et al in Climate Change 2013 The Physical ScienceBasis IPCC AR5 WGI report T Stocker et al Eds (CambridgeUniv Press Cambridge UK 2013) chap 7 pp 571ndash657

66 M Chin et al Multi-decadal aerosol variations from 1980 to2009 A perspective from observations and a global modelAtmos Chem Phys 14 3657ndash3690 (2014) doi 105194acp-14-3657-2014

67 V Ramanathan et al Atmospheric brown clouds Impacts onSouth Asian climate and hydrological cycle Proc Natl AcadSci USA 102 5326ndash5333 (2005) doi 101073pnas0500656102 pmid 15749818

68 M Cole P Lindeque C Halsband T S Galloway Microplasticsas contaminants in the marine environment A review MarPollut Bull 62 2588ndash2597 (2011) doi 101016jmarpolbul201109025 pmid 22001295

69 EEA (European Environment Agency) Genetically ModifiedOrganisms (GMOs) The Significance of Gene Flow ThroughPollen Transfer (Environmental Issue Report 28 EuropeanEnvironment Agency Copenhagen Denmark 2002)

70 J A Ivar do Sul M F Costa The present and future ofmicroplastic pollution in the marine environment Environ Pollut185 352ndash364 (2014) doi 101016jenvpol201310036pmid 24275078

71 R Kessler Engineered nanoparticles in consumer productsUnderstanding a new ingredient Environ Health Perspect 119a120ndasha125 (2011) doi 101289ehp119-a120 pmid 21356630

72 M Rees Our Final Century Will Civilisation Survive theTwenty-first Century (Arrow Books London 2003)

73 L M Persson et al Confronting unknown planetary boundarythreats from chemical pollution Environ Sci Technol 4712619ndash12622 (2013) doi 101021es402501c pmid 23980998

74 P P Egeghy et al The exposure data landscape formanufactured chemicals Sci Total Environ 414 159ndash166(2012) doi 101016jscitotenv201110046 pmid 22104386

75 UNEP (United Nations Environment Programme) GCOGlobal Chemicals Outlook Towards Sound Management ofChemicals (United Nations Environment ProgrammeNairobi Kenya 2013)

76 S Strempel M Scheringer C A Ng K HungerbuumlhlerScreening for PBT chemicals among the ldquoexistingrdquo andldquonewrdquo chemicals of the EU Environ Sci Technol 465680ndash5687 (2012) doi 101021es3002713pmid 22494215

77 M Scheringer et al How many persistent organic pollutantsshould we expect Atmos Poll Res 3 383ndash391 (2012)doi 105094APR2012044

78 K Sanderson Chemistry Itrsquos not easy being green Nature469 18ndash20 (2011) doi 101038469018a pmid 21209638

79 P A Schulte et al Occupational safety and health greenchemistry and sustainability A review of areas ofconvergence Environ Health 12 31 (2013) doi 1011861476-069X-12-31 pmid 23587312

80 EEA (European Environment Agency) Late Lessons from EarlyWarnings The Precautionary Principle 1896-2000 (EnvironmentalIssue Report 222001 Copenhagen Denmark 2001)

81 D Gee Late lessons from early warnings Toward realism andprecaution with endocrine-disrupting substances EnvironHealth Perspect 114 (suppl 1) 152ndash160 (2006) doi 101289ehp8134 pmid 16818262

82 T Lenton A Watson A Revolutions That Made the Earth(Oxford Univ Press Oxford UK 2011)

83 R Biggs et al Toward principles for enhancing the resilienceof ecosystem services Annu Rev Environ Resour 37421ndash448 (2012) doi 101146annurev-environ-051211-123836

84 G S Cumming P Olsson F S Chapin III C S HollingResilience experimentation and scale mismatches in social-ecological systems Landscape Ecol 28 1139ndash1150 (2013)doi 101007s10980-012-9725-4

85 D Griggs et al Policy Sustainable development goals forpeople and planet Nature 495 305ndash307 (2013) doi 101038495305a pmid 23518546

86 R Costanza Ed Ecological Economics The Science andManagement of Sustainability (Columbia Univ PressNew York 1991)

87 C Folke in Linking the Natural Environment and the EconomyEssays from the Eco-Eco Group C Folke T Karingberger Eds(Kluwer Academic Publishers Dordrecht Netherlands 1991)pp 77ndash94

88 L Robin S Soumlrlin P Warde Eds The Future of NatureDocuments of Global Change (Yale Univ Press New Haven CT2013)

89 U Heise Sense of Place and Sense of Planet TheEnvironmental Imagination of the Global (Oxford Univ PressOxford 2008)

90 M Scheffer Critical Transitions in Nature and Society(Princeton Univ Press Princeton NJ 2009)

91 J Masco Bad weather On planetary crisis Soc Stud Sci 407ndash40 (2010) doi 1011770306312709341598

92 G Paacutelsson et al Reconceptualizing the lsquoAnthroposrsquo in theAnthropocene Integrating the social sciences and humanitiesin global environmental change research Environ Sci Policy28 4 (2013) doi 101016jenvsci201211004

93 N Castree et al Changing the intellectual climate NatureClim Change 4 763ndash768 (2014) doi 101038nclimate2339

94 J M Anderies S R Carpenter W Steffen J Rockstroumlm Thetopology of non-linear global carbon dynamics From tippingpoints to planetary boundaries Environ Res Lett 8 044048(2013) doi 1010881748-932684044048

95 S E Cornell I C Prentice J I House C J DownyUnderstanding the Earth System Global Change Science forApplication (Cambridge Univ Press Cambridge 2012)

96 J A Dearing et al Safe and just operating spaces for regionalsocial-ecological systems Glob Environ Change 28 227ndash238(2014) doi 101016jgloenvcha201406012

ACKNOWLEDGMENTS

We thank J Foley and N Ramunkutty for contributions to theland-system change boundary A Pastor for analytical work on thePB for freshwater B Armstrong C Butler T McMichael andA Woodward for contributions to the novel entities boundary andB Scholes for comments on an earlier version of the manuscriptData associated with the paper are located at the StockholmResilience Centre Sweden (httpwwwstockholmresilienceorg21researchresearch-programmesplanetary-boundarieshtml)The planetary boundaries research at the Stockholm ResilienceCentre is made possible through a core grant from MISTRA(Swedish Foundation for Strategic Environmental Research) SECis supported by the Swedish Research Council EMB is supportedby the Natural Sciences and Engineering Research Council ofCanada and by the Trottier Institute for Science and Public PolicyRB is supported by a Branco Weiss Fellowship CF is supportedby the Family Erling Persson Academy Programme on GlobalEconomic Dynamics and the Biosphere IF is supported by theStordalen Foundation (Norway) SS is supported by theRiksbanken Jubileumsfond and the Institute for Advanced StudyPrinceton NJ and SRC and VR are supported bythe US National Science Foundation

SUPPLEMENTARY MATERIALS

wwwsciencemagorgcontent34762231259855supplDC1MethodsFigs S1 to S10Tables S1 to S3References (97ndash158)

11 August 2014 accepted 8 January 2015Published online 15 January 2015101126science1259855

1259855-10 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 sciencemagorg SCIENCE

RESEARCH | RESEARCH ARTICLE

DOI 101126science1259855 (2015)347 Science

et alWill SteffenplanetPlanetary boundaries Guiding human development on a changing

This copy is for your personal non-commercial use only

clicking herecolleagues clients or customers by you can order high-quality copies for yourIf you wish to distribute this article to others

herefollowing the guidelines

can be obtained byPermission to republish or repurpose articles or portions of articles

) February 12 2015 wwwsciencemagorg (this information is current as of

The following resources related to this article are available online at

httpwwwsciencemagorgcontent34762231259855fullhtmlversion of this article at

including high-resolution figures can be found in the onlineUpdated information and services

httpwwwsciencemagorgcontentsuppl20150114science1259855DC1html can be found at Supporting Online Material

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can berelated to this article A list of selected additional articles on the Science Web sites

httpwwwsciencemagorgcontent34762231259855fullhtmlref-list-1 27 of which can be accessed freecites 120 articlesThis article

httpwwwsciencemagorgcgicollectionecologyEcology

subject collectionsThis article appears in the following

registered trademark of AAAS is aScience2015 by the American Association for the Advancement of Science all rights reserved The title

CopyrightAmerican Association for the Advancement of Science 1200 New York Avenue NW Washington DC 20005 (print ISSN 0036-8075 online ISSN 1095-9203) is published weekly except the last week in December by theScience

on

Feb

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from

reversible The challenge to the research commu-nity is to develop the knowledge base that allowsthe screening of chemicals before they are re-leased into the environment for properties thatmay predispose them toward becoming globalproblemsAs a first step toward meeting this challenge

the three conditions outlined above have beenused as the basis for identifying scenarios ofchemical pollution that fulfill the conditions andas a next step for pinpointing chemical profilesthat fit the scenarios (28) This proposal consti-tutes a first attempt at adding the Earth-systemperspective when assessing hazard and risk ofchemicals and offers a vision for a systematic ap-proach to a complex management situation withmany unknownsDespite this progress in developing an Earth-

systemndashoriented approach there is not yet anaggregate global-level analysis of chemical pol-lution on which to base a control variable or aboundary value It may also serve little purposeto define boundary values and control varia-bles for a planetary boundary of this complexityNevertheless there is a potential threat fromnovel entities to disrupt the functioning of theEarth-system and society needs to learn how tomitigate these unknown risks and manage chem-icals under uncertainty (28 73)Some precautionary and preventive actions

can be considered These may include a strongerfocus on green chemistry (78) finding synergieswith risk-reducing interventions in other fieldssuch as occupational health (79) paying moreattention to learning from earlier mistakes (8081) and investing in science to better under-stand and monitor vital Earth-system processesin order to be able to detect disruptive effectsfrom novel entities as early as possible

Hierarchy of boundaries

An analysis of the many interactions among theboundaries (table S3 and fig S10) suggests thattwo of themmdashclimate change and biosphereintegritymdashare highly integrated emergent system-level phenomena that are connected to all of theother PBs They operate at the level of the wholeEarth system (7) and have coevolved for nearly4 billion years (82) They are regulated by theother boundaries and on the other hand pro-vide the planetary-level overarching systems with-in which the other boundary processes operateFurthermore large changes in the climate or inbiosphere integrity would likely on their ownpush the Earth system out of the Holocene stateIn fact transitions between time periods in Earthhistory have often been delineated by substantialshifts in climate the biosphere or both (82 83)These observations suggest a two-level hierar-

chy of boundaries in which climate change andbiosphere integrity should be recognized as coreplanetary boundaries through which the otherboundaries operate The crossing of one or moreof the other boundaries may seriously affect hu-man well-being and may predispose the trans-gression of a core boundary(ies) but does not byitself lead to a new state of the Earth system This

hierarchical approach to classifying the bounda-ries becomes clearer by examining inmore detailthe roles of climate and biosphere integrity in thefunctioning of the Earth systemThe climate system is a manifestation of the

amount distribution and net balance of energyat Earthrsquos surface The total amount of energysets the overall conditions for life In Earthrsquos cur-rent climate a range of global surface temper-atures and atmospheric pressures allows the threephases of water to be present simultaneouslywith ice and water vapor playing critical roles inthe physical feedbacks of the climate system Thedistribution of energy by latitude over the landand sea surfaces and within the ocean plays amajor role in the circulation of the two greatfluids the ocean and the atmosphere These sys-temic physical characteristics are key spatial de-terminants of the distribution of the biota andthe structure and functioning of ecosystems andare controllers of biogeochemical flowsBiosphere integrity is also crucial to Earth-

system functioning where the biosphere is de-fined as the totality of all ecosystems (terrestrialfreshwater andmarine) on Earth and their biota(32) These ecosystems and biota play a criticalrole in determining the state of the Earth systemregulating its material and energy flows and itsresponses to abrupt and gradual change (7) Di-versity in the biosphere provides resilience toterrestrial and marine ecosystems (83 84) Thebiosphere not only interacts with the other plan-etary boundaries but also increases the capacityof theEarth system topersist in a given state underchanges in these other boundaries The ultimatebasis for the many roles that the biosphere playsin Earth-system dynamics is the genetic code ofthe biota the basic information bank that de-fines the biospherersquos functional role and its ca-pacity to innovate and persist into the future

Planetary boundaries in asocietal context

A proposed approach for sustainable develop-ment goals (SDGs) (85) argues that the stablefunctioning of the Earth system is a prereq-uisite for thriving societies around the world Thisapproach implies that the PB framework orsomething like it will need to be implementedalongside the achievement of targets aimed atmore immediate human needs such as provi-sion of clean affordable and accessible energyand the adequate supply of food World devel-opment within the biophysical limits of a stableEarth system has always been a necessity [eg(86 87)] However only recently for a numberof reasons has it become possible to identifyevaluate and quantify risks of abrupt planetary-and biome-level shifts due to overshoot of keyEarth-system parameters (i) the emergence ofglobal-change thinking and Earth-system think-ing (88) (ii) the rise of ldquothe Planetaryrdquo as a rel-evant level of complex system understanding(89ndash92) and (iii) observable effects of the rapidincrease in human pressures on the planet (16)The PB approach is embedded in this emerg-

ing social context but it does not suggest how to

maneuver within the safe operating space in thequest for global sustainability For example thePB framework does not as yet account for the re-gional distribution of the impact or its histor-ical patterns Nor does the PB framework takeinto account the deeper issues of equity and cau-sation The current levels of the boundary pro-cesses and the transgressions of boundaries thathave already occurred are unevenly caused bydifferent human societies and different socialgroups The wealth benefits that these trans-gressions have brought are also unevenly distrib-uted socially and geographically It is easy toforesee that uneven distribution of causation andbenefits will continue and these differentialsmust surely be addressed for a Holocene-likeEarth-system state to be successfully legitimatedand maintained However the PB framework ascurrently construed provides no guidance as tohow this may be achieved [although some po-tential synergies have been noted (54)] and itcannot readily be used tomake choices betweenpathways for piecemeal maneuvering withinthe safe operating space ormore radical shifts ofglobal governance (93)The nature of the PB framework implies that

two important cautions should be observedwhenapplication of the framework to policy or man-agement is proposed boundary interactions andscale

Boundary interactions

The planetary boundaries framework arises fromthe scientific evidence that Earth is a singlecomplex integrated systemmdashthat is the bound-aries operate as an interdependent set [eg(94)] (table S1 and fig S10) Although a system-atic quantitative analysis of interactions amongall of the processes for which boundaries areproposed remains beyond the scope of currentmodeling and observational capacity the Earthsystem clearly operates in well-defined states inwhich these processes and their interactionscan create stabilizing or destabilizing feedbacks(16 90 95) This has profound implications forglobal sustainability because it emphasizes theneed to address multiple interacting environ-mental processes simultaneously (eg stabilizingthe climate system requires sustainable forestmanagement and stable ocean ecosystems)

Scale

The PB framework is not designed to be ldquodown-scaledrdquo or ldquodisaggregatedrdquo to smaller levels suchas nations or local communities That said thePB framework recognizes the importance ofchanges at the level of subsystems in the Earthsystem (eg biomes or large river basins) on thefunctioning of the Earth system as a whole Alsothere are strong arguments for an integrated ap-proach coupling boundary definitions at region-al and global levels with development goals toenable the application of ldquoPB thinkingrdquo at lev-els (nations basins and regions) where policyaction most commonly occurs [eg (85 96)]This update of the PB framework is one step on

a longer-term evolution of scientific knowledge to

1259855-8 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 sciencemagorg SCIENCE

RESEARCH | RESEARCH ARTICLE

inform and support global sustainability goalsand pathways This evolution is needed morethan ever before there are severe implementa-tion gaps inmany global environmental policiesrelating to the PB issues where problematictrends are not being halted or reversed despiteinternational consensus about the urgency of theproblems The prospect of tighter resource con-straints and rising environmental hazards is alsounavoidably turning the focus onto global socialequity and the planetary stewardship of Earthrsquoslife-support system There is a need for a trulyglobal evidence base with much greater integra-tion among issues in order to respond to theseglobal challenges New research initiatives [egFuture Earth (wwwfutureearthorg)] provide evi-dence that science can respond to this need byapplying Earth-system research to advance a newgeneration of integrated global analyses and toexplore options for transformations toward sus-tainability This is a clear sign that as the risksof the Anthropocene to human well-being be-come clearer research is maturing to a pointwhere a systemic step-change is possiblemdashandnecessarymdashin exploring and defining a safe andjust planetary operating space for the furtherdevelopment of human societies

Methods summary

Our approach to building the planetary bound-aries framework is described above We haveimplemented the framework through an ex-pert assessment and synthesis of the scientificknowledge of intrinsic biophysical processes thatregulate the stability of the Earth system Ourprecautionary approach is based on the main-tenance of a Holocene-like state of the Earthsystem and on an assessment of the level ofhuman-driven change that would risk destabi-lizing this state For the climate change PB thereis already much literature on which to basesuch an assessment For others such as strato-spheric ozone ocean acidification extinctionrates and P andN cycles we have used estimatesof preindustrial values of the control variableas a Holocene baseline Where large undesira-ble thresholds exist and have been studied (egpolar ice sheets Amazon rainforest aragonitedissolution atmospheric aerosols and the southAsian monsoon) quantitative boundaries can bereadily proposed For others where the focus ison erosion of Earth-system resilience the bound-aries are more difficult (but not impossible) toquantify as reflected in larger uncertainty zonesWe used large-scale assessments of the impacts

of human activities on Earth-system functioning[eg Intergovernmental Panel on Climate Change(17 18) the International Geosphere-BiosphereProgramme synthesis (16) and chemicals (75 80)]as sources of community-level understandingon which to propose PBs Our update has alsorelied on post-2009 assessments of individualboundaries by the relevant expert research com-munities examples include phosphorus (3) ni-trogen (5) biosphere integrity (7) freshwater use(5 63) and novel entities [with a focus on chem-icals (28 73)] Finally some new analyses have

been undertaken specifically for this paper (i) afreshwater-use PB based on the EWF approach(33 63) (ii) the linkage of the phosphorus andnitrogen boundaries via the NP ratio in grow-ing crop tissue (33) and (iii) the use of majorforest biomes as the basis for the land-systemchange PB (33)

REFERENCES AND NOTES

1 J Rockstroumlm et al Planetary boundaries Exploring the safeoperating space for humanity Ecol Soc 14 32 (2009)httpwwwecologyandsocietyorgvol14iss2art32

2 J Rockstroumlm et al A safe operating space for humanityNature 461 472ndash475 (2009) doi 101038461472apmid 19779433

3 S R Carpenter E M Bennett Reconsideration of theplanetary boundary for phosphorus Environ Res Lett 6014009 (2011) doi 1010881748-932661014009

4 S W Running Ecology A measurable planetary boundaryfor the biosphere Science 337 1458ndash1459 (2012)doi 101126science1227620 pmid 22997311

5 W de Vries J Kros C Kroeze S P Seitzinger Assessingplanetary and regional nitrogen boundaries related to foodsecurity and adverse environmental impacts Curr OpinionEnviron Sust 5 392ndash402 (2013) doi 101016jcosust201307004

6 D Gerten et al Towards a revised planetary boundary forconsumptive freshwater use Role of environmental flowrequirements Curr Opinion Environ Sust 5 551ndash558 (2013)doi 101016jcosust201311001

7 G M Mace et al Approaches to defining a planetary boundaryfor biodiversity Glob Environ Change 28 289ndash297 (2014)doi 101016jgloenvcha201407009

8 V Galaz Global Environmental Governance Technology andPolitics The Anthropocene Gap (Edward Elgar CheltenhamUK 2014)

9 UN GSP (UN High-Level Panel on Global Sustainability)Resilient People Resilient Planet A Future Worth Choosing(Report for the 2012 Rio+20 Earth Summit United NationsNew York 2012)

10 WBCSD (World Business Council on Sustainable Development)Action 2020 Overview (WBCSD Geneva Switzerlandhttpaction2020org accessed 18 June 2014)

11 R Costanza L Graumlich W Steffen Eds Integrated Historyand Future of People on Earth (MIT Press CambridgeMA USA 2006)

12 S Soumlrlin P Warde in Naturersquos End History and theEnvironment S Soumlrlin P Warde Eds (Palgrave MacMillanLondon 2009) pp 1ndash19

13 R C Bishop Endangered species and uncertainty Theeconomics of a safe minimum standard Am J Agric Econ 6110ndash18 (1978) doi 1023071240156

14 T M Crowards Safe minimum standards Costs andopportunities Ecol Econ 25 303ndash314 (1998) doi 101016S0921-8009(97)00041-4

15 W Steffen J Crutzen J R McNeill The Anthropocene Arehumans now overwhelming the great forces of NatureAmbio 36 614ndash621 (2007) doi 1015790044-7447(2007)36[614TAAHNO]20CO2 pmid 18240674

16 W Steffen et al Global Change and the Earth System A PlanetUnder Pressure (The IGBP Book Series Springer-VerlagBerlin Heidelberg New York 2004)

17 IPCC (Intergovernmental Panel on Climate Change) Managingthe risks of extreme events and disasters to advanceclimate change adaptation A special report of Working GroupsI and II of the IPCC CB Field et al Eds (CambridgeUniversity Press Cambridge UK (2012) doi 101017CBO9781139177245

18 IPCC (Intergovernmental Panel on Climate Change) ClimateChange 2013 The Physical Science Basis Summary forPolicymakers L Alexander et al Eds (IPCC SecretariatGeneva Switzerland 2013) doi 101017CBO9781107415324

19 P J Crutzen Geology of mankind Nature 415 23 (2002)doi 101038415023a pmid 11780095

20 K Richardson W Steffen D Liverman Climate Change GlobalRisks Challenges and Decisions (Cambridge Univ PressCambridge UK 2011)

21 T M Lenton et al Tipping elements in the Earthrsquos climatesystem Proc Natl Acad Sci USA 105 1786ndash1793 (2008)doi 101073pnas0705414105 pmid 18258748

22 M Scheffer et al Early-warning signals for criticaltransitions Nature 461 53ndash59 (2009) doi 101038nature08227 pmid 19727193

23 S R Carpenter W A Brock Rising variance A leadingindicator of ecological transition Ecol Lett 9 311ndash318 (2006)doi 101111j1461-0248200500877x pmid 16958897

24 J Bakke et al Rapid oceanic and atmospheric changes duringthe Younger Dryas cold period Nat Geosci 2 202ndash205(2009) doi 101038ngeo439

25 M Scheffer et al Anticipating critical transitions Science338 344ndash348 (2012) doi 101126science1225244pmid 23087241

26 R Wang et al Flickering gives early warning signals of acritical transition to a eutrophic lake state Nature 492419ndash422 (2012) doi 101038nature11655 pmid 23160492

27 R Biggs S R Carpenter W A Brock Turning back fromthe brink Detecting an impending regime shift in time to avertit Proc Natl Acad Sci USA 106 826ndash831 (2009)doi 101073pnas0811729106 pmid 19124774

28 M MacLeod et al Identifying chemicals that are planetaryboundary threats Environ Sci Technol 48 11057ndash11063(2014) doi 101021es501893m pmid 25181298

29 C S Holling Resilience and stability of ecological systemsAnnu Rev Ecol Syst 4 1ndash23 (1973) doi 101146annureves04110173000245

30 C Folke et al Resilience thinking Integrating resilienceadaptability and transformability Ecol Soc 15 20 (2010)wwwecologyandsocietyorgvol15iss4art20

31 T P Hughes S Carpenter J Rockstroumlm M SchefferB Walker Multiscale regime shifts and planetary boundariesTrends Ecol Evol 28 389ndash395 (2013) doi 101016jtree201305019 pmid 23769417

32 T M Lenton H T P Williams On the origin of planetary-scaletipping points Trends Ecol Evol 28 380ndash382 (2013)doi 101016jtree201306001 pmid 23777818

33 Supplementary text figures and tables are available onScience Online

34 NOAA (National Oceanic and Atmospheric Administration)NOAA-ESRL Annual CO2 Data accessed at httpco2noworgCurrent-CO2CO2-Nowannual-co2html (2014)

35 S E Perkins L V Alexander J Nairn Increasing frequencyintensity and duration of observed global heat waves and warmspells Geophys Res Lett 39 L20714 (2012) doi 1010292012GL053361

36 A Shepherd et al A reconciled estimate of ice-sheet massbalance Science 338 1183ndash1189 (2012) doi 101126science1228102 pmid 23197528

37 M R Helmus T J Bland C K Williams A R IvesPhylogenetic measures of biodiversity Am Nat 169 E68ndashE83(2007) doi 101086511334 pmid 17230400

38 S Drsquoagata et al Human-mediated loss of phylogeneticand functional diversity in coral reef fishes Curr Biol24 555ndash560 (2014) doi 101016jcub201401049pmid 24560574

39 A D Barnosky et al Has the Earthrsquos sixth mass extinctionalready arrived Nature 471 51ndash57 (2011) doi 101038nature09678 pmid 21368823

40 N W Mason F de Bello D Mouillot S Pavoine S Dray Aguide for using functional diversity indices to reveal changesin assembly processes along ecological gradients J VegSci 24 794ndash806 (2013) doi 101111jvs12013

41 R J Scholes R Biggs A biodiversity intactness index Nature434 45ndash49 (2005) doi 101038nature03289pmid 15744293

42 B Cardinale Ecology Impacts of biodiversity loss Science336 552ndash553 (2012) doi 101126science1222102pmid 22556243

43 D U Hooper et al A global synthesis reveals biodiversityloss as a major driver of ecosystem change Nature 486105ndash108 (2012) doi 101038nature11118pmid 22678289

44 BAS (British Antarctic Survey) ldquoAntarctic ozonerdquo wwwantarcticaacukmetjdsozoneindexhtmldata J ShanklinBritish Antarctic Survey (2013)

45 Royal Society Ocean Acidification Due to IncreasingAtmospheric Carbon Dioxide Policy Document 1205 (TheRoyal Society London 2005)

46 J M Guinotte V J Fabry Ocean acidification and its potentialeffects on marine ecosystems Ann N Y Acad Sci 1134320ndash342 (2008) doi 101196annals1439013pmid 18566099

47 D J Conley Terrestrial ecosystems and the globalbiogeochemical silica cycle Global Biogeochem Cycles 16681ndash688 (2002) doi 1010292002GB001894

SCIENCE sciencemagorg 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 1259855-9

RESEARCH | RESEARCH ARTICLE

48 F Vandevenne E Struyf W Clymans P Meire Agriculturalsilica harvest Have humans created a new loop in the globalsilica cycle Front Ecol Environ 10 243ndash248 (2012)doi 101890110046

49 S E Gress T D Nichols C C Northcraft W T PeterjohnNutrient limitation in soils exhibiting differing nitrogenavailabilities What lies beyond nitrogen saturation Ecol 88119ndash130 (2007) doi 1018900012-9658(2007)88[119NLISED]20CO2 pmid 17489460

50 H Hillebrand V Lehmpfuhl Resource stoichiometry andconsumers control the biodiversity-productivity relationship inpelagic metacommunities Am Nat 178 171ndash181 (2011)doi 101086660831 pmid 21750381

51 C M Moore et al Processes and patterns of oceanic nutrientlimitation Nat Geosci 6 701ndash710 (2013) doi 101038ngeo1765

52 G K MacDonald E M Bennett P A Potter N RamankuttyAgronomic phosphorus imbalances across the worldrsquoscroplands Proc Natl Acad Sci USA 108 3086ndash3091 (2011)doi 101073pnas1010808108 pmid 21282605

53 L Bouwman et al Exploring global changes in nitrogen andphosphorus cycles in agriculture induced by livestockproduction over the 1900-2050 period Proc Natl AcadSci USA 110 20882ndash20887 (2013) doi 101073pnas1012878108 pmid 21576477

54 W Steffen M Stafford Smith Planetary boundaries equityand global sustainability Why wealthy countries could benefitfrom more equity Curr Opinion Environ Sust 5 403ndash408(2013) doi 101016jcosust201304007

55 D J Greenwood et al A unifying concept for the dependenceof whole-crop N P ratio on biomass theory and experimentAnn Bot (Lond) 102 967ndash977 (2008) doi 101093aobmcn188 pmid 18840873

56 P K Snyder C Delire J A Foley Evaluating the influence ofdifferent vegetation biomes on the global climate Clim Dyn23 279ndash302 (2004) doi 101007s00382-004-0430-0

57 P C West G T Narisma C C Barford C J KucharikJ A Foley An alternative approach for quantifying climateregulation by ecosystems Front Ecol Environ 9 126ndash133(2010) doi 101890090015

58 EPI (Earth Policy Institute) ldquoForest coverrdquo wwwearthpolicyorgindicatorsC56forests_2012_ (2014)

59 M Falkenmark Meeting water requirements of an expandingworld population Philos Trans R Soc Lond B Biol Sci 352929ndash936 (1997) doi 101098rstb19970072

60 J S Wallace M C Acreman C A Sullivan The sharing ofwater between society and ecosystems From conflict tocatchment-based co-management Philos Trans R Soc LondB Biol Sci 358 2011ndash2026 (2003) doi 101098rstb20031383 pmid 14728795

61 N L Poff et al The natural flow regime A paradigm for riverconservation and restoration BioSci 47 769ndash784 (1997)doi 1023071313099

62 N L Poff J K H Zimmerman Ecological responses to alteredflow regimes A literature review to inform the science andmanagement of environmental flows Biol 55 194ndash205 (2010)doi 101111j1365-2427200902272x

63 A V Pastor F Ludwig H Biemans H Hoff P KabatAccounting for environmental flow requirements in globalwater assessments Hydrol Earth Syst Sci 18 5041ndash5059(2014) doi 105194hess-18-5041-2014

64 WHO (World Health Organization) Burden of Disease from theJoint Effects of Household and Ambient Air Pollution for 2012(wwwwhointphehealth_topicsoutdoorairdatabasesFINAL_HAP_AAP_BoD24March2014pdf accessed 23 June 2014httpwwwwhointphehealth_topicsoutdoorairdatabasesen)

65 O Boucher et al in Climate Change 2013 The Physical ScienceBasis IPCC AR5 WGI report T Stocker et al Eds (CambridgeUniv Press Cambridge UK 2013) chap 7 pp 571ndash657

66 M Chin et al Multi-decadal aerosol variations from 1980 to2009 A perspective from observations and a global modelAtmos Chem Phys 14 3657ndash3690 (2014) doi 105194acp-14-3657-2014

67 V Ramanathan et al Atmospheric brown clouds Impacts onSouth Asian climate and hydrological cycle Proc Natl AcadSci USA 102 5326ndash5333 (2005) doi 101073pnas0500656102 pmid 15749818

68 M Cole P Lindeque C Halsband T S Galloway Microplasticsas contaminants in the marine environment A review MarPollut Bull 62 2588ndash2597 (2011) doi 101016jmarpolbul201109025 pmid 22001295

69 EEA (European Environment Agency) Genetically ModifiedOrganisms (GMOs) The Significance of Gene Flow ThroughPollen Transfer (Environmental Issue Report 28 EuropeanEnvironment Agency Copenhagen Denmark 2002)

70 J A Ivar do Sul M F Costa The present and future ofmicroplastic pollution in the marine environment Environ Pollut185 352ndash364 (2014) doi 101016jenvpol201310036pmid 24275078

71 R Kessler Engineered nanoparticles in consumer productsUnderstanding a new ingredient Environ Health Perspect 119a120ndasha125 (2011) doi 101289ehp119-a120 pmid 21356630

72 M Rees Our Final Century Will Civilisation Survive theTwenty-first Century (Arrow Books London 2003)

73 L M Persson et al Confronting unknown planetary boundarythreats from chemical pollution Environ Sci Technol 4712619ndash12622 (2013) doi 101021es402501c pmid 23980998

74 P P Egeghy et al The exposure data landscape formanufactured chemicals Sci Total Environ 414 159ndash166(2012) doi 101016jscitotenv201110046 pmid 22104386

75 UNEP (United Nations Environment Programme) GCOGlobal Chemicals Outlook Towards Sound Management ofChemicals (United Nations Environment ProgrammeNairobi Kenya 2013)

76 S Strempel M Scheringer C A Ng K HungerbuumlhlerScreening for PBT chemicals among the ldquoexistingrdquo andldquonewrdquo chemicals of the EU Environ Sci Technol 465680ndash5687 (2012) doi 101021es3002713pmid 22494215

77 M Scheringer et al How many persistent organic pollutantsshould we expect Atmos Poll Res 3 383ndash391 (2012)doi 105094APR2012044

78 K Sanderson Chemistry Itrsquos not easy being green Nature469 18ndash20 (2011) doi 101038469018a pmid 21209638

79 P A Schulte et al Occupational safety and health greenchemistry and sustainability A review of areas ofconvergence Environ Health 12 31 (2013) doi 1011861476-069X-12-31 pmid 23587312

80 EEA (European Environment Agency) Late Lessons from EarlyWarnings The Precautionary Principle 1896-2000 (EnvironmentalIssue Report 222001 Copenhagen Denmark 2001)

81 D Gee Late lessons from early warnings Toward realism andprecaution with endocrine-disrupting substances EnvironHealth Perspect 114 (suppl 1) 152ndash160 (2006) doi 101289ehp8134 pmid 16818262

82 T Lenton A Watson A Revolutions That Made the Earth(Oxford Univ Press Oxford UK 2011)

83 R Biggs et al Toward principles for enhancing the resilienceof ecosystem services Annu Rev Environ Resour 37421ndash448 (2012) doi 101146annurev-environ-051211-123836

84 G S Cumming P Olsson F S Chapin III C S HollingResilience experimentation and scale mismatches in social-ecological systems Landscape Ecol 28 1139ndash1150 (2013)doi 101007s10980-012-9725-4

85 D Griggs et al Policy Sustainable development goals forpeople and planet Nature 495 305ndash307 (2013) doi 101038495305a pmid 23518546

86 R Costanza Ed Ecological Economics The Science andManagement of Sustainability (Columbia Univ PressNew York 1991)

87 C Folke in Linking the Natural Environment and the EconomyEssays from the Eco-Eco Group C Folke T Karingberger Eds(Kluwer Academic Publishers Dordrecht Netherlands 1991)pp 77ndash94

88 L Robin S Soumlrlin P Warde Eds The Future of NatureDocuments of Global Change (Yale Univ Press New Haven CT2013)

89 U Heise Sense of Place and Sense of Planet TheEnvironmental Imagination of the Global (Oxford Univ PressOxford 2008)

90 M Scheffer Critical Transitions in Nature and Society(Princeton Univ Press Princeton NJ 2009)

91 J Masco Bad weather On planetary crisis Soc Stud Sci 407ndash40 (2010) doi 1011770306312709341598

92 G Paacutelsson et al Reconceptualizing the lsquoAnthroposrsquo in theAnthropocene Integrating the social sciences and humanitiesin global environmental change research Environ Sci Policy28 4 (2013) doi 101016jenvsci201211004

93 N Castree et al Changing the intellectual climate NatureClim Change 4 763ndash768 (2014) doi 101038nclimate2339

94 J M Anderies S R Carpenter W Steffen J Rockstroumlm Thetopology of non-linear global carbon dynamics From tippingpoints to planetary boundaries Environ Res Lett 8 044048(2013) doi 1010881748-932684044048

95 S E Cornell I C Prentice J I House C J DownyUnderstanding the Earth System Global Change Science forApplication (Cambridge Univ Press Cambridge 2012)

96 J A Dearing et al Safe and just operating spaces for regionalsocial-ecological systems Glob Environ Change 28 227ndash238(2014) doi 101016jgloenvcha201406012

ACKNOWLEDGMENTS

We thank J Foley and N Ramunkutty for contributions to theland-system change boundary A Pastor for analytical work on thePB for freshwater B Armstrong C Butler T McMichael andA Woodward for contributions to the novel entities boundary andB Scholes for comments on an earlier version of the manuscriptData associated with the paper are located at the StockholmResilience Centre Sweden (httpwwwstockholmresilienceorg21researchresearch-programmesplanetary-boundarieshtml)The planetary boundaries research at the Stockholm ResilienceCentre is made possible through a core grant from MISTRA(Swedish Foundation for Strategic Environmental Research) SECis supported by the Swedish Research Council EMB is supportedby the Natural Sciences and Engineering Research Council ofCanada and by the Trottier Institute for Science and Public PolicyRB is supported by a Branco Weiss Fellowship CF is supportedby the Family Erling Persson Academy Programme on GlobalEconomic Dynamics and the Biosphere IF is supported by theStordalen Foundation (Norway) SS is supported by theRiksbanken Jubileumsfond and the Institute for Advanced StudyPrinceton NJ and SRC and VR are supported bythe US National Science Foundation

SUPPLEMENTARY MATERIALS

wwwsciencemagorgcontent34762231259855supplDC1MethodsFigs S1 to S10Tables S1 to S3References (97ndash158)

11 August 2014 accepted 8 January 2015Published online 15 January 2015101126science1259855

1259855-10 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 sciencemagorg SCIENCE

RESEARCH | RESEARCH ARTICLE

DOI 101126science1259855 (2015)347 Science

et alWill SteffenplanetPlanetary boundaries Guiding human development on a changing

This copy is for your personal non-commercial use only

clicking herecolleagues clients or customers by you can order high-quality copies for yourIf you wish to distribute this article to others

herefollowing the guidelines

can be obtained byPermission to republish or repurpose articles or portions of articles

) February 12 2015 wwwsciencemagorg (this information is current as of

The following resources related to this article are available online at

httpwwwsciencemagorgcontent34762231259855fullhtmlversion of this article at

including high-resolution figures can be found in the onlineUpdated information and services

httpwwwsciencemagorgcontentsuppl20150114science1259855DC1html can be found at Supporting Online Material

httpwwwsciencemagorgcontent34762231259855fullhtmlrelatedfound at

can berelated to this article A list of selected additional articles on the Science Web sites

httpwwwsciencemagorgcontent34762231259855fullhtmlref-list-1 27 of which can be accessed freecites 120 articlesThis article

httpwwwsciencemagorgcgicollectionecologyEcology

subject collectionsThis article appears in the following

registered trademark of AAAS is aScience2015 by the American Association for the Advancement of Science all rights reserved The title

CopyrightAmerican Association for the Advancement of Science 1200 New York Avenue NW Washington DC 20005 (print ISSN 0036-8075 online ISSN 1095-9203) is published weekly except the last week in December by theScience

on

Feb

ruar

y 13

201

5w

ww

sci

ence

mag

org

Dow

nloa

ded

from

inform and support global sustainability goalsand pathways This evolution is needed morethan ever before there are severe implementa-tion gaps inmany global environmental policiesrelating to the PB issues where problematictrends are not being halted or reversed despiteinternational consensus about the urgency of theproblems The prospect of tighter resource con-straints and rising environmental hazards is alsounavoidably turning the focus onto global socialequity and the planetary stewardship of Earthrsquoslife-support system There is a need for a trulyglobal evidence base with much greater integra-tion among issues in order to respond to theseglobal challenges New research initiatives [egFuture Earth (wwwfutureearthorg)] provide evi-dence that science can respond to this need byapplying Earth-system research to advance a newgeneration of integrated global analyses and toexplore options for transformations toward sus-tainability This is a clear sign that as the risksof the Anthropocene to human well-being be-come clearer research is maturing to a pointwhere a systemic step-change is possiblemdashandnecessarymdashin exploring and defining a safe andjust planetary operating space for the furtherdevelopment of human societies

Methods summary

Our approach to building the planetary bound-aries framework is described above We haveimplemented the framework through an ex-pert assessment and synthesis of the scientificknowledge of intrinsic biophysical processes thatregulate the stability of the Earth system Ourprecautionary approach is based on the main-tenance of a Holocene-like state of the Earthsystem and on an assessment of the level ofhuman-driven change that would risk destabi-lizing this state For the climate change PB thereis already much literature on which to basesuch an assessment For others such as strato-spheric ozone ocean acidification extinctionrates and P andN cycles we have used estimatesof preindustrial values of the control variableas a Holocene baseline Where large undesira-ble thresholds exist and have been studied (egpolar ice sheets Amazon rainforest aragonitedissolution atmospheric aerosols and the southAsian monsoon) quantitative boundaries can bereadily proposed For others where the focus ison erosion of Earth-system resilience the bound-aries are more difficult (but not impossible) toquantify as reflected in larger uncertainty zonesWe used large-scale assessments of the impacts

of human activities on Earth-system functioning[eg Intergovernmental Panel on Climate Change(17 18) the International Geosphere-BiosphereProgramme synthesis (16) and chemicals (75 80)]as sources of community-level understandingon which to propose PBs Our update has alsorelied on post-2009 assessments of individualboundaries by the relevant expert research com-munities examples include phosphorus (3) ni-trogen (5) biosphere integrity (7) freshwater use(5 63) and novel entities [with a focus on chem-icals (28 73)] Finally some new analyses have

been undertaken specifically for this paper (i) afreshwater-use PB based on the EWF approach(33 63) (ii) the linkage of the phosphorus andnitrogen boundaries via the NP ratio in grow-ing crop tissue (33) and (iii) the use of majorforest biomes as the basis for the land-systemchange PB (33)

REFERENCES AND NOTES

1 J Rockstroumlm et al Planetary boundaries Exploring the safeoperating space for humanity Ecol Soc 14 32 (2009)httpwwwecologyandsocietyorgvol14iss2art32

2 J Rockstroumlm et al A safe operating space for humanityNature 461 472ndash475 (2009) doi 101038461472apmid 19779433

3 S R Carpenter E M Bennett Reconsideration of theplanetary boundary for phosphorus Environ Res Lett 6014009 (2011) doi 1010881748-932661014009

4 S W Running Ecology A measurable planetary boundaryfor the biosphere Science 337 1458ndash1459 (2012)doi 101126science1227620 pmid 22997311

5 W de Vries J Kros C Kroeze S P Seitzinger Assessingplanetary and regional nitrogen boundaries related to foodsecurity and adverse environmental impacts Curr OpinionEnviron Sust 5 392ndash402 (2013) doi 101016jcosust201307004

6 D Gerten et al Towards a revised planetary boundary forconsumptive freshwater use Role of environmental flowrequirements Curr Opinion Environ Sust 5 551ndash558 (2013)doi 101016jcosust201311001

7 G M Mace et al Approaches to defining a planetary boundaryfor biodiversity Glob Environ Change 28 289ndash297 (2014)doi 101016jgloenvcha201407009

8 V Galaz Global Environmental Governance Technology andPolitics The Anthropocene Gap (Edward Elgar CheltenhamUK 2014)

9 UN GSP (UN High-Level Panel on Global Sustainability)Resilient People Resilient Planet A Future Worth Choosing(Report for the 2012 Rio+20 Earth Summit United NationsNew York 2012)

10 WBCSD (World Business Council on Sustainable Development)Action 2020 Overview (WBCSD Geneva Switzerlandhttpaction2020org accessed 18 June 2014)

11 R Costanza L Graumlich W Steffen Eds Integrated Historyand Future of People on Earth (MIT Press CambridgeMA USA 2006)

12 S Soumlrlin P Warde in Naturersquos End History and theEnvironment S Soumlrlin P Warde Eds (Palgrave MacMillanLondon 2009) pp 1ndash19

13 R C Bishop Endangered species and uncertainty Theeconomics of a safe minimum standard Am J Agric Econ 6110ndash18 (1978) doi 1023071240156

14 T M Crowards Safe minimum standards Costs andopportunities Ecol Econ 25 303ndash314 (1998) doi 101016S0921-8009(97)00041-4

15 W Steffen J Crutzen J R McNeill The Anthropocene Arehumans now overwhelming the great forces of NatureAmbio 36 614ndash621 (2007) doi 1015790044-7447(2007)36[614TAAHNO]20CO2 pmid 18240674

16 W Steffen et al Global Change and the Earth System A PlanetUnder Pressure (The IGBP Book Series Springer-VerlagBerlin Heidelberg New York 2004)

17 IPCC (Intergovernmental Panel on Climate Change) Managingthe risks of extreme events and disasters to advanceclimate change adaptation A special report of Working GroupsI and II of the IPCC CB Field et al Eds (CambridgeUniversity Press Cambridge UK (2012) doi 101017CBO9781139177245

18 IPCC (Intergovernmental Panel on Climate Change) ClimateChange 2013 The Physical Science Basis Summary forPolicymakers L Alexander et al Eds (IPCC SecretariatGeneva Switzerland 2013) doi 101017CBO9781107415324

19 P J Crutzen Geology of mankind Nature 415 23 (2002)doi 101038415023a pmid 11780095

20 K Richardson W Steffen D Liverman Climate Change GlobalRisks Challenges and Decisions (Cambridge Univ PressCambridge UK 2011)

21 T M Lenton et al Tipping elements in the Earthrsquos climatesystem Proc Natl Acad Sci USA 105 1786ndash1793 (2008)doi 101073pnas0705414105 pmid 18258748

22 M Scheffer et al Early-warning signals for criticaltransitions Nature 461 53ndash59 (2009) doi 101038nature08227 pmid 19727193

23 S R Carpenter W A Brock Rising variance A leadingindicator of ecological transition Ecol Lett 9 311ndash318 (2006)doi 101111j1461-0248200500877x pmid 16958897

24 J Bakke et al Rapid oceanic and atmospheric changes duringthe Younger Dryas cold period Nat Geosci 2 202ndash205(2009) doi 101038ngeo439

25 M Scheffer et al Anticipating critical transitions Science338 344ndash348 (2012) doi 101126science1225244pmid 23087241

26 R Wang et al Flickering gives early warning signals of acritical transition to a eutrophic lake state Nature 492419ndash422 (2012) doi 101038nature11655 pmid 23160492

27 R Biggs S R Carpenter W A Brock Turning back fromthe brink Detecting an impending regime shift in time to avertit Proc Natl Acad Sci USA 106 826ndash831 (2009)doi 101073pnas0811729106 pmid 19124774

28 M MacLeod et al Identifying chemicals that are planetaryboundary threats Environ Sci Technol 48 11057ndash11063(2014) doi 101021es501893m pmid 25181298

29 C S Holling Resilience and stability of ecological systemsAnnu Rev Ecol Syst 4 1ndash23 (1973) doi 101146annureves04110173000245

30 C Folke et al Resilience thinking Integrating resilienceadaptability and transformability Ecol Soc 15 20 (2010)wwwecologyandsocietyorgvol15iss4art20

31 T P Hughes S Carpenter J Rockstroumlm M SchefferB Walker Multiscale regime shifts and planetary boundariesTrends Ecol Evol 28 389ndash395 (2013) doi 101016jtree201305019 pmid 23769417

32 T M Lenton H T P Williams On the origin of planetary-scaletipping points Trends Ecol Evol 28 380ndash382 (2013)doi 101016jtree201306001 pmid 23777818

33 Supplementary text figures and tables are available onScience Online

34 NOAA (National Oceanic and Atmospheric Administration)NOAA-ESRL Annual CO2 Data accessed at httpco2noworgCurrent-CO2CO2-Nowannual-co2html (2014)

35 S E Perkins L V Alexander J Nairn Increasing frequencyintensity and duration of observed global heat waves and warmspells Geophys Res Lett 39 L20714 (2012) doi 1010292012GL053361

36 A Shepherd et al A reconciled estimate of ice-sheet massbalance Science 338 1183ndash1189 (2012) doi 101126science1228102 pmid 23197528

37 M R Helmus T J Bland C K Williams A R IvesPhylogenetic measures of biodiversity Am Nat 169 E68ndashE83(2007) doi 101086511334 pmid 17230400

38 S Drsquoagata et al Human-mediated loss of phylogeneticand functional diversity in coral reef fishes Curr Biol24 555ndash560 (2014) doi 101016jcub201401049pmid 24560574

39 A D Barnosky et al Has the Earthrsquos sixth mass extinctionalready arrived Nature 471 51ndash57 (2011) doi 101038nature09678 pmid 21368823

40 N W Mason F de Bello D Mouillot S Pavoine S Dray Aguide for using functional diversity indices to reveal changesin assembly processes along ecological gradients J VegSci 24 794ndash806 (2013) doi 101111jvs12013

41 R J Scholes R Biggs A biodiversity intactness index Nature434 45ndash49 (2005) doi 101038nature03289pmid 15744293

42 B Cardinale Ecology Impacts of biodiversity loss Science336 552ndash553 (2012) doi 101126science1222102pmid 22556243

43 D U Hooper et al A global synthesis reveals biodiversityloss as a major driver of ecosystem change Nature 486105ndash108 (2012) doi 101038nature11118pmid 22678289

44 BAS (British Antarctic Survey) ldquoAntarctic ozonerdquo wwwantarcticaacukmetjdsozoneindexhtmldata J ShanklinBritish Antarctic Survey (2013)

45 Royal Society Ocean Acidification Due to IncreasingAtmospheric Carbon Dioxide Policy Document 1205 (TheRoyal Society London 2005)

46 J M Guinotte V J Fabry Ocean acidification and its potentialeffects on marine ecosystems Ann N Y Acad Sci 1134320ndash342 (2008) doi 101196annals1439013pmid 18566099

47 D J Conley Terrestrial ecosystems and the globalbiogeochemical silica cycle Global Biogeochem Cycles 16681ndash688 (2002) doi 1010292002GB001894

SCIENCE sciencemagorg 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 1259855-9

RESEARCH | RESEARCH ARTICLE

48 F Vandevenne E Struyf W Clymans P Meire Agriculturalsilica harvest Have humans created a new loop in the globalsilica cycle Front Ecol Environ 10 243ndash248 (2012)doi 101890110046

49 S E Gress T D Nichols C C Northcraft W T PeterjohnNutrient limitation in soils exhibiting differing nitrogenavailabilities What lies beyond nitrogen saturation Ecol 88119ndash130 (2007) doi 1018900012-9658(2007)88[119NLISED]20CO2 pmid 17489460

50 H Hillebrand V Lehmpfuhl Resource stoichiometry andconsumers control the biodiversity-productivity relationship inpelagic metacommunities Am Nat 178 171ndash181 (2011)doi 101086660831 pmid 21750381

51 C M Moore et al Processes and patterns of oceanic nutrientlimitation Nat Geosci 6 701ndash710 (2013) doi 101038ngeo1765

52 G K MacDonald E M Bennett P A Potter N RamankuttyAgronomic phosphorus imbalances across the worldrsquoscroplands Proc Natl Acad Sci USA 108 3086ndash3091 (2011)doi 101073pnas1010808108 pmid 21282605

53 L Bouwman et al Exploring global changes in nitrogen andphosphorus cycles in agriculture induced by livestockproduction over the 1900-2050 period Proc Natl AcadSci USA 110 20882ndash20887 (2013) doi 101073pnas1012878108 pmid 21576477

54 W Steffen M Stafford Smith Planetary boundaries equityand global sustainability Why wealthy countries could benefitfrom more equity Curr Opinion Environ Sust 5 403ndash408(2013) doi 101016jcosust201304007

55 D J Greenwood et al A unifying concept for the dependenceof whole-crop N P ratio on biomass theory and experimentAnn Bot (Lond) 102 967ndash977 (2008) doi 101093aobmcn188 pmid 18840873

56 P K Snyder C Delire J A Foley Evaluating the influence ofdifferent vegetation biomes on the global climate Clim Dyn23 279ndash302 (2004) doi 101007s00382-004-0430-0

57 P C West G T Narisma C C Barford C J KucharikJ A Foley An alternative approach for quantifying climateregulation by ecosystems Front Ecol Environ 9 126ndash133(2010) doi 101890090015

58 EPI (Earth Policy Institute) ldquoForest coverrdquo wwwearthpolicyorgindicatorsC56forests_2012_ (2014)

59 M Falkenmark Meeting water requirements of an expandingworld population Philos Trans R Soc Lond B Biol Sci 352929ndash936 (1997) doi 101098rstb19970072

60 J S Wallace M C Acreman C A Sullivan The sharing ofwater between society and ecosystems From conflict tocatchment-based co-management Philos Trans R Soc LondB Biol Sci 358 2011ndash2026 (2003) doi 101098rstb20031383 pmid 14728795

61 N L Poff et al The natural flow regime A paradigm for riverconservation and restoration BioSci 47 769ndash784 (1997)doi 1023071313099

62 N L Poff J K H Zimmerman Ecological responses to alteredflow regimes A literature review to inform the science andmanagement of environmental flows Biol 55 194ndash205 (2010)doi 101111j1365-2427200902272x

63 A V Pastor F Ludwig H Biemans H Hoff P KabatAccounting for environmental flow requirements in globalwater assessments Hydrol Earth Syst Sci 18 5041ndash5059(2014) doi 105194hess-18-5041-2014

64 WHO (World Health Organization) Burden of Disease from theJoint Effects of Household and Ambient Air Pollution for 2012(wwwwhointphehealth_topicsoutdoorairdatabasesFINAL_HAP_AAP_BoD24March2014pdf accessed 23 June 2014httpwwwwhointphehealth_topicsoutdoorairdatabasesen)

65 O Boucher et al in Climate Change 2013 The Physical ScienceBasis IPCC AR5 WGI report T Stocker et al Eds (CambridgeUniv Press Cambridge UK 2013) chap 7 pp 571ndash657

66 M Chin et al Multi-decadal aerosol variations from 1980 to2009 A perspective from observations and a global modelAtmos Chem Phys 14 3657ndash3690 (2014) doi 105194acp-14-3657-2014

67 V Ramanathan et al Atmospheric brown clouds Impacts onSouth Asian climate and hydrological cycle Proc Natl AcadSci USA 102 5326ndash5333 (2005) doi 101073pnas0500656102 pmid 15749818

68 M Cole P Lindeque C Halsband T S Galloway Microplasticsas contaminants in the marine environment A review MarPollut Bull 62 2588ndash2597 (2011) doi 101016jmarpolbul201109025 pmid 22001295

69 EEA (European Environment Agency) Genetically ModifiedOrganisms (GMOs) The Significance of Gene Flow ThroughPollen Transfer (Environmental Issue Report 28 EuropeanEnvironment Agency Copenhagen Denmark 2002)

70 J A Ivar do Sul M F Costa The present and future ofmicroplastic pollution in the marine environment Environ Pollut185 352ndash364 (2014) doi 101016jenvpol201310036pmid 24275078

71 R Kessler Engineered nanoparticles in consumer productsUnderstanding a new ingredient Environ Health Perspect 119a120ndasha125 (2011) doi 101289ehp119-a120 pmid 21356630

72 M Rees Our Final Century Will Civilisation Survive theTwenty-first Century (Arrow Books London 2003)

73 L M Persson et al Confronting unknown planetary boundarythreats from chemical pollution Environ Sci Technol 4712619ndash12622 (2013) doi 101021es402501c pmid 23980998

74 P P Egeghy et al The exposure data landscape formanufactured chemicals Sci Total Environ 414 159ndash166(2012) doi 101016jscitotenv201110046 pmid 22104386

75 UNEP (United Nations Environment Programme) GCOGlobal Chemicals Outlook Towards Sound Management ofChemicals (United Nations Environment ProgrammeNairobi Kenya 2013)

76 S Strempel M Scheringer C A Ng K HungerbuumlhlerScreening for PBT chemicals among the ldquoexistingrdquo andldquonewrdquo chemicals of the EU Environ Sci Technol 465680ndash5687 (2012) doi 101021es3002713pmid 22494215

77 M Scheringer et al How many persistent organic pollutantsshould we expect Atmos Poll Res 3 383ndash391 (2012)doi 105094APR2012044

78 K Sanderson Chemistry Itrsquos not easy being green Nature469 18ndash20 (2011) doi 101038469018a pmid 21209638

79 P A Schulte et al Occupational safety and health greenchemistry and sustainability A review of areas ofconvergence Environ Health 12 31 (2013) doi 1011861476-069X-12-31 pmid 23587312

80 EEA (European Environment Agency) Late Lessons from EarlyWarnings The Precautionary Principle 1896-2000 (EnvironmentalIssue Report 222001 Copenhagen Denmark 2001)

81 D Gee Late lessons from early warnings Toward realism andprecaution with endocrine-disrupting substances EnvironHealth Perspect 114 (suppl 1) 152ndash160 (2006) doi 101289ehp8134 pmid 16818262

82 T Lenton A Watson A Revolutions That Made the Earth(Oxford Univ Press Oxford UK 2011)

83 R Biggs et al Toward principles for enhancing the resilienceof ecosystem services Annu Rev Environ Resour 37421ndash448 (2012) doi 101146annurev-environ-051211-123836

84 G S Cumming P Olsson F S Chapin III C S HollingResilience experimentation and scale mismatches in social-ecological systems Landscape Ecol 28 1139ndash1150 (2013)doi 101007s10980-012-9725-4

85 D Griggs et al Policy Sustainable development goals forpeople and planet Nature 495 305ndash307 (2013) doi 101038495305a pmid 23518546

86 R Costanza Ed Ecological Economics The Science andManagement of Sustainability (Columbia Univ PressNew York 1991)

87 C Folke in Linking the Natural Environment and the EconomyEssays from the Eco-Eco Group C Folke T Karingberger Eds(Kluwer Academic Publishers Dordrecht Netherlands 1991)pp 77ndash94

88 L Robin S Soumlrlin P Warde Eds The Future of NatureDocuments of Global Change (Yale Univ Press New Haven CT2013)

89 U Heise Sense of Place and Sense of Planet TheEnvironmental Imagination of the Global (Oxford Univ PressOxford 2008)

90 M Scheffer Critical Transitions in Nature and Society(Princeton Univ Press Princeton NJ 2009)

91 J Masco Bad weather On planetary crisis Soc Stud Sci 407ndash40 (2010) doi 1011770306312709341598

92 G Paacutelsson et al Reconceptualizing the lsquoAnthroposrsquo in theAnthropocene Integrating the social sciences and humanitiesin global environmental change research Environ Sci Policy28 4 (2013) doi 101016jenvsci201211004

93 N Castree et al Changing the intellectual climate NatureClim Change 4 763ndash768 (2014) doi 101038nclimate2339

94 J M Anderies S R Carpenter W Steffen J Rockstroumlm Thetopology of non-linear global carbon dynamics From tippingpoints to planetary boundaries Environ Res Lett 8 044048(2013) doi 1010881748-932684044048

95 S E Cornell I C Prentice J I House C J DownyUnderstanding the Earth System Global Change Science forApplication (Cambridge Univ Press Cambridge 2012)

96 J A Dearing et al Safe and just operating spaces for regionalsocial-ecological systems Glob Environ Change 28 227ndash238(2014) doi 101016jgloenvcha201406012

ACKNOWLEDGMENTS

We thank J Foley and N Ramunkutty for contributions to theland-system change boundary A Pastor for analytical work on thePB for freshwater B Armstrong C Butler T McMichael andA Woodward for contributions to the novel entities boundary andB Scholes for comments on an earlier version of the manuscriptData associated with the paper are located at the StockholmResilience Centre Sweden (httpwwwstockholmresilienceorg21researchresearch-programmesplanetary-boundarieshtml)The planetary boundaries research at the Stockholm ResilienceCentre is made possible through a core grant from MISTRA(Swedish Foundation for Strategic Environmental Research) SECis supported by the Swedish Research Council EMB is supportedby the Natural Sciences and Engineering Research Council ofCanada and by the Trottier Institute for Science and Public PolicyRB is supported by a Branco Weiss Fellowship CF is supportedby the Family Erling Persson Academy Programme on GlobalEconomic Dynamics and the Biosphere IF is supported by theStordalen Foundation (Norway) SS is supported by theRiksbanken Jubileumsfond and the Institute for Advanced StudyPrinceton NJ and SRC and VR are supported bythe US National Science Foundation

SUPPLEMENTARY MATERIALS

wwwsciencemagorgcontent34762231259855supplDC1MethodsFigs S1 to S10Tables S1 to S3References (97ndash158)

11 August 2014 accepted 8 January 2015Published online 15 January 2015101126science1259855

1259855-10 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 sciencemagorg SCIENCE

RESEARCH | RESEARCH ARTICLE

DOI 101126science1259855 (2015)347 Science

et alWill SteffenplanetPlanetary boundaries Guiding human development on a changing

This copy is for your personal non-commercial use only

clicking herecolleagues clients or customers by you can order high-quality copies for yourIf you wish to distribute this article to others

herefollowing the guidelines

can be obtained byPermission to republish or repurpose articles or portions of articles

) February 12 2015 wwwsciencemagorg (this information is current as of

The following resources related to this article are available online at

httpwwwsciencemagorgcontent34762231259855fullhtmlversion of this article at

including high-resolution figures can be found in the onlineUpdated information and services

httpwwwsciencemagorgcontentsuppl20150114science1259855DC1html can be found at Supporting Online Material

httpwwwsciencemagorgcontent34762231259855fullhtmlrelatedfound at

can berelated to this article A list of selected additional articles on the Science Web sites

httpwwwsciencemagorgcontent34762231259855fullhtmlref-list-1 27 of which can be accessed freecites 120 articlesThis article

httpwwwsciencemagorgcgicollectionecologyEcology

subject collectionsThis article appears in the following

registered trademark of AAAS is aScience2015 by the American Association for the Advancement of Science all rights reserved The title

CopyrightAmerican Association for the Advancement of Science 1200 New York Avenue NW Washington DC 20005 (print ISSN 0036-8075 online ISSN 1095-9203) is published weekly except the last week in December by theScience

on

Feb

ruar

y 13

201

5w

ww

sci

ence

mag

org

Dow

nloa

ded

from

48 F Vandevenne E Struyf W Clymans P Meire Agriculturalsilica harvest Have humans created a new loop in the globalsilica cycle Front Ecol Environ 10 243ndash248 (2012)doi 101890110046

49 S E Gress T D Nichols C C Northcraft W T PeterjohnNutrient limitation in soils exhibiting differing nitrogenavailabilities What lies beyond nitrogen saturation Ecol 88119ndash130 (2007) doi 1018900012-9658(2007)88[119NLISED]20CO2 pmid 17489460

50 H Hillebrand V Lehmpfuhl Resource stoichiometry andconsumers control the biodiversity-productivity relationship inpelagic metacommunities Am Nat 178 171ndash181 (2011)doi 101086660831 pmid 21750381

51 C M Moore et al Processes and patterns of oceanic nutrientlimitation Nat Geosci 6 701ndash710 (2013) doi 101038ngeo1765

52 G K MacDonald E M Bennett P A Potter N RamankuttyAgronomic phosphorus imbalances across the worldrsquoscroplands Proc Natl Acad Sci USA 108 3086ndash3091 (2011)doi 101073pnas1010808108 pmid 21282605

53 L Bouwman et al Exploring global changes in nitrogen andphosphorus cycles in agriculture induced by livestockproduction over the 1900-2050 period Proc Natl AcadSci USA 110 20882ndash20887 (2013) doi 101073pnas1012878108 pmid 21576477

54 W Steffen M Stafford Smith Planetary boundaries equityand global sustainability Why wealthy countries could benefitfrom more equity Curr Opinion Environ Sust 5 403ndash408(2013) doi 101016jcosust201304007

55 D J Greenwood et al A unifying concept for the dependenceof whole-crop N P ratio on biomass theory and experimentAnn Bot (Lond) 102 967ndash977 (2008) doi 101093aobmcn188 pmid 18840873

56 P K Snyder C Delire J A Foley Evaluating the influence ofdifferent vegetation biomes on the global climate Clim Dyn23 279ndash302 (2004) doi 101007s00382-004-0430-0

57 P C West G T Narisma C C Barford C J KucharikJ A Foley An alternative approach for quantifying climateregulation by ecosystems Front Ecol Environ 9 126ndash133(2010) doi 101890090015

58 EPI (Earth Policy Institute) ldquoForest coverrdquo wwwearthpolicyorgindicatorsC56forests_2012_ (2014)

59 M Falkenmark Meeting water requirements of an expandingworld population Philos Trans R Soc Lond B Biol Sci 352929ndash936 (1997) doi 101098rstb19970072

60 J S Wallace M C Acreman C A Sullivan The sharing ofwater between society and ecosystems From conflict tocatchment-based co-management Philos Trans R Soc LondB Biol Sci 358 2011ndash2026 (2003) doi 101098rstb20031383 pmid 14728795

61 N L Poff et al The natural flow regime A paradigm for riverconservation and restoration BioSci 47 769ndash784 (1997)doi 1023071313099

62 N L Poff J K H Zimmerman Ecological responses to alteredflow regimes A literature review to inform the science andmanagement of environmental flows Biol 55 194ndash205 (2010)doi 101111j1365-2427200902272x

63 A V Pastor F Ludwig H Biemans H Hoff P KabatAccounting for environmental flow requirements in globalwater assessments Hydrol Earth Syst Sci 18 5041ndash5059(2014) doi 105194hess-18-5041-2014

64 WHO (World Health Organization) Burden of Disease from theJoint Effects of Household and Ambient Air Pollution for 2012(wwwwhointphehealth_topicsoutdoorairdatabasesFINAL_HAP_AAP_BoD24March2014pdf accessed 23 June 2014httpwwwwhointphehealth_topicsoutdoorairdatabasesen)

65 O Boucher et al in Climate Change 2013 The Physical ScienceBasis IPCC AR5 WGI report T Stocker et al Eds (CambridgeUniv Press Cambridge UK 2013) chap 7 pp 571ndash657

66 M Chin et al Multi-decadal aerosol variations from 1980 to2009 A perspective from observations and a global modelAtmos Chem Phys 14 3657ndash3690 (2014) doi 105194acp-14-3657-2014

67 V Ramanathan et al Atmospheric brown clouds Impacts onSouth Asian climate and hydrological cycle Proc Natl AcadSci USA 102 5326ndash5333 (2005) doi 101073pnas0500656102 pmid 15749818

68 M Cole P Lindeque C Halsband T S Galloway Microplasticsas contaminants in the marine environment A review MarPollut Bull 62 2588ndash2597 (2011) doi 101016jmarpolbul201109025 pmid 22001295

69 EEA (European Environment Agency) Genetically ModifiedOrganisms (GMOs) The Significance of Gene Flow ThroughPollen Transfer (Environmental Issue Report 28 EuropeanEnvironment Agency Copenhagen Denmark 2002)

70 J A Ivar do Sul M F Costa The present and future ofmicroplastic pollution in the marine environment Environ Pollut185 352ndash364 (2014) doi 101016jenvpol201310036pmid 24275078

71 R Kessler Engineered nanoparticles in consumer productsUnderstanding a new ingredient Environ Health Perspect 119a120ndasha125 (2011) doi 101289ehp119-a120 pmid 21356630

72 M Rees Our Final Century Will Civilisation Survive theTwenty-first Century (Arrow Books London 2003)

73 L M Persson et al Confronting unknown planetary boundarythreats from chemical pollution Environ Sci Technol 4712619ndash12622 (2013) doi 101021es402501c pmid 23980998

74 P P Egeghy et al The exposure data landscape formanufactured chemicals Sci Total Environ 414 159ndash166(2012) doi 101016jscitotenv201110046 pmid 22104386

75 UNEP (United Nations Environment Programme) GCOGlobal Chemicals Outlook Towards Sound Management ofChemicals (United Nations Environment ProgrammeNairobi Kenya 2013)

76 S Strempel M Scheringer C A Ng K HungerbuumlhlerScreening for PBT chemicals among the ldquoexistingrdquo andldquonewrdquo chemicals of the EU Environ Sci Technol 465680ndash5687 (2012) doi 101021es3002713pmid 22494215

77 M Scheringer et al How many persistent organic pollutantsshould we expect Atmos Poll Res 3 383ndash391 (2012)doi 105094APR2012044

78 K Sanderson Chemistry Itrsquos not easy being green Nature469 18ndash20 (2011) doi 101038469018a pmid 21209638

79 P A Schulte et al Occupational safety and health greenchemistry and sustainability A review of areas ofconvergence Environ Health 12 31 (2013) doi 1011861476-069X-12-31 pmid 23587312

80 EEA (European Environment Agency) Late Lessons from EarlyWarnings The Precautionary Principle 1896-2000 (EnvironmentalIssue Report 222001 Copenhagen Denmark 2001)

81 D Gee Late lessons from early warnings Toward realism andprecaution with endocrine-disrupting substances EnvironHealth Perspect 114 (suppl 1) 152ndash160 (2006) doi 101289ehp8134 pmid 16818262

82 T Lenton A Watson A Revolutions That Made the Earth(Oxford Univ Press Oxford UK 2011)

83 R Biggs et al Toward principles for enhancing the resilienceof ecosystem services Annu Rev Environ Resour 37421ndash448 (2012) doi 101146annurev-environ-051211-123836

84 G S Cumming P Olsson F S Chapin III C S HollingResilience experimentation and scale mismatches in social-ecological systems Landscape Ecol 28 1139ndash1150 (2013)doi 101007s10980-012-9725-4

85 D Griggs et al Policy Sustainable development goals forpeople and planet Nature 495 305ndash307 (2013) doi 101038495305a pmid 23518546

86 R Costanza Ed Ecological Economics The Science andManagement of Sustainability (Columbia Univ PressNew York 1991)

87 C Folke in Linking the Natural Environment and the EconomyEssays from the Eco-Eco Group C Folke T Karingberger Eds(Kluwer Academic Publishers Dordrecht Netherlands 1991)pp 77ndash94

88 L Robin S Soumlrlin P Warde Eds The Future of NatureDocuments of Global Change (Yale Univ Press New Haven CT2013)

89 U Heise Sense of Place and Sense of Planet TheEnvironmental Imagination of the Global (Oxford Univ PressOxford 2008)

90 M Scheffer Critical Transitions in Nature and Society(Princeton Univ Press Princeton NJ 2009)

91 J Masco Bad weather On planetary crisis Soc Stud Sci 407ndash40 (2010) doi 1011770306312709341598

92 G Paacutelsson et al Reconceptualizing the lsquoAnthroposrsquo in theAnthropocene Integrating the social sciences and humanitiesin global environmental change research Environ Sci Policy28 4 (2013) doi 101016jenvsci201211004

93 N Castree et al Changing the intellectual climate NatureClim Change 4 763ndash768 (2014) doi 101038nclimate2339

94 J M Anderies S R Carpenter W Steffen J Rockstroumlm Thetopology of non-linear global carbon dynamics From tippingpoints to planetary boundaries Environ Res Lett 8 044048(2013) doi 1010881748-932684044048

95 S E Cornell I C Prentice J I House C J DownyUnderstanding the Earth System Global Change Science forApplication (Cambridge Univ Press Cambridge 2012)

96 J A Dearing et al Safe and just operating spaces for regionalsocial-ecological systems Glob Environ Change 28 227ndash238(2014) doi 101016jgloenvcha201406012

ACKNOWLEDGMENTS

We thank J Foley and N Ramunkutty for contributions to theland-system change boundary A Pastor for analytical work on thePB for freshwater B Armstrong C Butler T McMichael andA Woodward for contributions to the novel entities boundary andB Scholes for comments on an earlier version of the manuscriptData associated with the paper are located at the StockholmResilience Centre Sweden (httpwwwstockholmresilienceorg21researchresearch-programmesplanetary-boundarieshtml)The planetary boundaries research at the Stockholm ResilienceCentre is made possible through a core grant from MISTRA(Swedish Foundation for Strategic Environmental Research) SECis supported by the Swedish Research Council EMB is supportedby the Natural Sciences and Engineering Research Council ofCanada and by the Trottier Institute for Science and Public PolicyRB is supported by a Branco Weiss Fellowship CF is supportedby the Family Erling Persson Academy Programme on GlobalEconomic Dynamics and the Biosphere IF is supported by theStordalen Foundation (Norway) SS is supported by theRiksbanken Jubileumsfond and the Institute for Advanced StudyPrinceton NJ and SRC and VR are supported bythe US National Science Foundation

SUPPLEMENTARY MATERIALS

wwwsciencemagorgcontent34762231259855supplDC1MethodsFigs S1 to S10Tables S1 to S3References (97ndash158)

11 August 2014 accepted 8 January 2015Published online 15 January 2015101126science1259855

1259855-10 13 FEBRUARY 2015 bull VOL 347 ISSUE 6223 sciencemagorg SCIENCE

RESEARCH | RESEARCH ARTICLE

DOI 101126science1259855 (2015)347 Science

et alWill SteffenplanetPlanetary boundaries Guiding human development on a changing

This copy is for your personal non-commercial use only

clicking herecolleagues clients or customers by you can order high-quality copies for yourIf you wish to distribute this article to others

herefollowing the guidelines

can be obtained byPermission to republish or repurpose articles or portions of articles

) February 12 2015 wwwsciencemagorg (this information is current as of

The following resources related to this article are available online at

httpwwwsciencemagorgcontent34762231259855fullhtmlversion of this article at

including high-resolution figures can be found in the onlineUpdated information and services

httpwwwsciencemagorgcontentsuppl20150114science1259855DC1html can be found at Supporting Online Material

httpwwwsciencemagorgcontent34762231259855fullhtmlrelatedfound at

can berelated to this article A list of selected additional articles on the Science Web sites

httpwwwsciencemagorgcontent34762231259855fullhtmlref-list-1 27 of which can be accessed freecites 120 articlesThis article

httpwwwsciencemagorgcgicollectionecologyEcology

subject collectionsThis article appears in the following

registered trademark of AAAS is aScience2015 by the American Association for the Advancement of Science all rights reserved The title

CopyrightAmerican Association for the Advancement of Science 1200 New York Avenue NW Washington DC 20005 (print ISSN 0036-8075 online ISSN 1095-9203) is published weekly except the last week in December by theScience

on

Feb

ruar

y 13

201

5w

ww

sci

ence

mag

org

Dow

nloa

ded

from

DOI 101126science1259855 (2015)347 Science

et alWill SteffenplanetPlanetary boundaries Guiding human development on a changing

This copy is for your personal non-commercial use only

clicking herecolleagues clients or customers by you can order high-quality copies for yourIf you wish to distribute this article to others

herefollowing the guidelines

can be obtained byPermission to republish or repurpose articles or portions of articles

) February 12 2015 wwwsciencemagorg (this information is current as of

The following resources related to this article are available online at

httpwwwsciencemagorgcontent34762231259855fullhtmlversion of this article at

including high-resolution figures can be found in the onlineUpdated information and services

httpwwwsciencemagorgcontentsuppl20150114science1259855DC1html can be found at Supporting Online Material

httpwwwsciencemagorgcontent34762231259855fullhtmlrelatedfound at

can berelated to this article A list of selected additional articles on the Science Web sites

httpwwwsciencemagorgcontent34762231259855fullhtmlref-list-1 27 of which can be accessed freecites 120 articlesThis article

httpwwwsciencemagorgcgicollectionecologyEcology

subject collectionsThis article appears in the following

registered trademark of AAAS is aScience2015 by the American Association for the Advancement of Science all rights reserved The title

CopyrightAmerican Association for the Advancement of Science 1200 New York Avenue NW Washington DC 20005 (print ISSN 0036-8075 online ISSN 1095-9203) is published weekly except the last week in December by theScience

on

Feb

ruar

y 13

201

5w

ww

sci

ence

mag

org

Dow

nloa

ded

from