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Climate changeand plant extinction
Andrew D. FriendLaboratoire des Sciences du Climat
et de l’Environnement (LSCE)Gif-sur-Yvette
Friday, 9 February, 2007
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extinction
« cessation of existence of a species or group of taxa, reducing biodiversity »
Golden Toad, lastseen 15 May, 1989,Costa Rica
Passenger pigeon,N. America,extinct 1901
Dodo, Mauritius,extinct <1700
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extinction
only 1/1000 of all species are still alive(i.e. almost all species that have everexisted are now extinct - extinction isnormal)
but, over time, biodiversity hasincreased…
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numbers of species:Kingdom described estimated totalBacteria 4,000 1,000,000Protoctists 80,000 600,000Animals 1,320,000 10,600,000Fungi 70,000 1,500,000Plants 270,000 300,000
TOTAL 1,744,000 ca. 14,000,000
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Plant evolution
Source: Elizabeth Anne Viau
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• 500 mya to land– more CO2, nutrients, and light
• But: problems (drivers of evolution)– Intense competition for light
• Elevated display of foliar elements– Water stress
• Cuticle, stomata, extensive roots, phenology, tracheids, herbaceous
– Fire• Herbaceous habit
– Limited N supply (competition from microbes)
• Leaf structure and display• Symbiotic N-fixation, NO3
- use– Freezing
• Deciduous• Protective compounds
– Herbivory• Grass habit, protective compounds, elevated
display– Photorespiration
• C4 photosynthesis• Followed by evolution of decomposing
organisms– Bacteria, fungi, soil fauna
plant evolution > diversity
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…plantdiversity
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Extinction rates• Extinctions over past 400 years:
– 337 vertebrates– 389 invertebrates– 90+ plants
• mammals and birds: 0.5 extinctions/yr• Geological rate?
– spp. average lifespan = 4 million yr– 10 million spp.– therefore, 10/4 = 2.5 extinctions/yr– So, now (10000/15) is 100-200x background rate
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Why important: plant metabolites
• Antimicrobial• Antifungal• Antiviral• Chemotherapy
– Taxol (from Pacificyew tree)
– Vincristine (fromMadagascar periwinkle)
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Why important: food crops• New Species• New Genes
– drought tolerance– salt tolerance
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Reasons for extinctions:
• habitat destruction– agriculture, logging, development
• exploitation• invasion• climate/environmental change
Global Temperature Trends
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Credit: NASA
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Future???
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future extinctions:
• 15-37% of land plants and animals lost by 2050 due to climate change (1-2+ °C) (Thomas et al., 2004)
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Calculating risksfrom climate change
• Niche-based models– « niche » = ecological space– relates spp. distribution to climate
• « climate envolope »– future climate scenario > spp. move, or die?– depends on
• amount of climate change• dispersal
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Vegetation distribution : potential natural vegetation(BIOME4; Kaplan et al., 2003)
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Whittaker (1975): climate envelopes
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Almond-leaved willow
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now
climate parameters
• precipitation– mean annual– winter– summer
• temperature– mean annual– minimum– growing degree days
• soil moisture
2050
rainfall
tem
pera
ture
Withoutmigration
with migration
criticallyendangered
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source: Thuiller et al., 2005. Climatechange threats to biodiversity inEurope. PNAS 102, 8254.
Proportion of species classified according to the IUCN Red Listassessment under two extremes assumptions about species migration.EX, extinct; CR, critically endangered; EN, endangered; VU, vulnerable;LR, lower risk. Predictions for 2080.
22% CR
2% EX
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source: Thuiller et al., 2005. Climatechange threats to biodiversity inEurope. PNAS 102, 8254.
Estimated percentage of species loss and turnover. Upper extreme, upperquartile, median, lower quartile, and lower extreme are represented foreach box.
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species loss rates
• main causes:– growing-degree days– moisture availability
• >80% loss– northcentral Spain– Cevennes– Massif Central
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source: Thuiller et al., 2005. Climatechange threats to biodiversity inEurope. PNAS 102, 8254.
Relationships between the percentage of species loss and anomalies ofmoisture availability and growing-degree days. The colours correspond todifferent climate change scenarios.
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source: Thuiller et al., 2005. Climatechange threats to biodiversity inEurope. PNAS 102, 8254.
Regional projections of the residuals from the multiple regression of speciesloss against growing-degree days and moisture availability. Red colours indicatean excess of species loss; grey colours indicate a deficit.
RED:specialized speciesmarginal habitats
Gray:hot and drytolerant species
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source: Thuiller et al., 2005. Climatechange threats to biodiversity inEurope. PNAS 102, 8254.
Spatial sensitivity of plant diversity in Europe ranked by biogeographic regions.Mean percentage of current species richness (Left) and species loss (Center)and turnover (Right) by environmental zones under the A1-HadCM3 scenario.
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conclusions
• Considerable risks to biodiversity fromclimate change in Europe
• Greatest vulnerability in mountain regions• Least vulnerability in southern
Mediterranean and Pannonian regions• Transition zone key for plant-species
conservation in a changing climate
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avoiding mass extinctions
• avoid climate change• reduce emissions• move plants• design reserves
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it is said:
• « we’re sitting at the edge of a massextinction » Root et al. (2003)
BUT, is that really true???
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big unknown: direct effect of CO2
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plants need:
• light• warmth• water• nutrients
– CO2
– nitrogen– phosphorus, etc.
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plants grow better
• with more CO2
• especially at higher temperatures!
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cond
ucta
nce
CO2
data: beech (Forstreuter, 1998)
2xCO2
++N
+26% -40% -29%
+158% +65% +48%
Anet gleaf Eleaf data: beech(Friend & Leith)
RH
-19%
+10%
CO2 supply and transpiration
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increased CO2:
• increased photosynthesis• reduced evapotranspiration• increased leaf area• increased growth rate• reduced heat stress• reduced moisture stress• all especially at higher temperatures!
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source: Kim & Leith, 2003
how to build a model (1) : fundamental growth processes
photosynthesis responsesRosa hybrida L.
○ data – model
A/Ci responses at 10 and 20 °C. B, A/Ci responses at 30 and 40 °C. C, Temperature response at three Ca levels (µbar). D, Light response at Ca of350 µbar at 25 °C. Relative humidity was maintained around 50 %.
A/Ci responses at two incident PAR levels (70 and 200 µmol m–2 s–1) at 25 °C. B, Light response at Ca of 1000 µbar at 25 °C. C, Temperature response at three Ca levels underincident PAR of 200 µmol m–2 s–1. D, Light response of leaves of different age (30, 68 and 180 d after unfolding) at ambient CO2 (350 µbar) at 25 °C. Relative humidity wasmaintained around 50 %.
LI-6400
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what limits plant growth?
• term: Net Primary Production (NPP)– basically, growth rate
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Potential climate limits to plant growth derived from long-termmonthly statistics of minimum temperature, cloud cover, and rainfall
Nemani et al., Science June 6th 2003
potential climate limits:water (red), sunlight (green), temperature (blue)
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NPP increases:
Figure 16. Trends in NPP 1981-1999 computed using the PEM, driven by AVHRR NDVI.
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Woody encroachment
• Invasion of woody plant species into savannas and grasslands
• Widespread globally• Why?
– Land use: grazing, fire suppression?
– Climate, exotic species, rising CO2 also implicated
• Increase C storage• Detrimental for grazing
1903 vs 1941, Santa Rita range, AZ(http://ag.arizona.edu/research/archer/research/biblio1.html)
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MOD15_BU LAI and FPAR: 1- and 4-km, monthly
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spatial pattern of greening
From Zhou et al., (JGR, 2001)
Analyses of pixel-based persistence indices from GIMMS (v1) NDVI data for the period 1981 to 1999 indicate that:
About 61% of the total vegetated area between 40N-70N in Eurasia shows a persistent increase in growing season NDVI over a broad contiguous swath of land from Central Europe through Siberia to the Aldan plateau, where almost 58% (7.3 million km2) is forests and woodlands.
North America, in comparison, shows a fragmented pattern of change, notable only in the forests of the southeast and grasslands of the upper Midwest.
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1. Are the sink mechanisms permanent features?
time
Sink
St r
eng t
h
3. Will they saturate?
time
Sink
St r
eng t
h
2. Will they increasein strength?
time
Sink
St r
eng t
h
4. Will they disappear?
timeSi
nk S
t ren
g th
Future Dynamics of C Sink Mechanisms
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need to build:
• process-based, mechanistic computer models of plant growth and environmentalresponses...
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major science questions• Physiological processes• Controls on plant distribution and production• Responses to forcings, past, present and
future– Climate change– Increasing [CO2], [O3], Ndep– Land use and Management
• Roles of terrestrial ecosystems for– Climate– Biogeochemistry
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key processes invegetation models
• Photosynthesis• Respiration• Stomatal conductance• Nutrient uptake• Partitioning and growth• Phenology• Reproduction• Competition• Herbivory, fire, and disease• Mortality
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how to build a model (1) : fundamental growth processes
photosynthesis(Farquhar model)
( )( )
( )( )
Γ+Γ−
++Γ−
=*
**
max
24;
/1min
i
i
oici
i
CCJ
KOKCCVA
carboxylationcapacity
RuBPregeneration
[CO2][O2]
Photorespirationcompensationpoint
Michaelis-Mentenconstants
Michaelis-Mentenkinetics
rubi
sco chlorophyll
Modélisation de la végétation,lundi 24 avril, CEREGE
Photosynthesis
-20
-10
0
10
20
30
40
50
0 20 40 60 80 100
CO2 concentratation (mmol m-3)
Phot
osyn
thes
is (u
mol
m-2
s-1
)
[ ][ ] mKSSVV+
= max
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CO2
photosynthesisCO2
respiration
how to build a process-based vegetation model : fundamental growth processes
nutrientuptake
N, P
litter production
C, N, P
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GC=fTxCl/MT
meristemcontrol
water (ΒD)
light (Phyt)
GN,P(f,r)=GC(f,r)xN,Pl/Cl
GN,P(w)=0.1GN,P
how to build a model (1) : fundamental growth processes
partitioning
Nl/ClPl/Cl
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how to build a model (4) : biological interactions and dynamics
competition, space and temporal dynamics
large variation in methods
•big-leaf, NPP•horizontal•vertical
•gap model•individual-based
•statistical
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how to build a model (5) : forcing
physical environment
many approaches
•prescribed•monthly, daily, hourly
•weather generator•PBL coupling•Mesoscale coupling•GCM coupling
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1990s
2080s
what models tell us : climate change impacts
Hybrid DGVM
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Coupled vegetation/climate global leaf canopy CO2 fluxes
gC/m2/daygC/m2/day
canopy C-flux canopy C-flux change (2070-1860)
(annual total flux = 121 PgC/yr) (flux change = +47%; climate only: -9%)
FEEDBACKS...
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state of knowledge:highly uncertain
• Many European species could be threatened by climatechange. Under the assumption of no migration, more than half of the species...become vulnerable or committed to extinction by 2080. Thuiller et al. (2005)
• The CO2-induced global warming extinction hypothesisclaims...many species of plants and animals will not beable to migrate either poleward in latitude or upward in elevation fast enough to avoid extinction as they try to escape the stress imposed by the rising temperature. ...[but, in fact] the ranges of most of earth’s plants willlikely expand if the planet continues to warm, makingplant extinctions even less likely than they are currently. Idso (2003)
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lots more work to do...
HYBRID6 GPT(NPP)
GPT
NLEVs NLEVt BREVs BREVt BRDDt C3g C4g BRCDt moss NLCDt
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FIN
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