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IAP STATEMENT ON OCEAN ACIDIFICATION

Headline messages

OceansplayacriticalroleintheglobalcarboncyclebyabsorbingaboutaquarterotheCO2emittedtotheatmosphereromhumanactivities;

TherapidincreaseinCO2emissionssincetheindustrialrevolutionhasincreasedtheacidityotheworldsoceanswithpotentiallyprooundconsequencesormarineplantsandanimalsespeciallythosethatrequirecalciumcarbonatetogrowandsurvive,andotherspeciesthatrelyontheseorood;

Atcurrentemissionratesmodelssuggestthatallcoralreesandpolarecosystemswillbeseverelyaectedby2050orpotentiallyevenearlier;

Marineoodsuppliesarelikelytobereducedwithsignifcantimplicationsoroodproductionandsecurityinregionsdependentonfshprotein,andhumanhealthandwellbeing;

Oceanacidifcationisirreversibleontimescalesoatleasttensothousandsoyears;

EvenwithstabilisationoatmosphericCO2at450ppm,oceanacidifcationwillhaveprooundimpactsonmanymarinesystems.LargeandrapidreductionsoglobalCO 2emissionsareneededgloballybyatleast50%by2050.

1. CO2 and ocean chemistry

Overthepast200years,theoceanshaveabsorbedapproximatelyaquarterotheCO 2producedromhumanactivities.ThisCO2wouldotherwisehaveaccumulatedintheatmosphereleadingtogreaterclimatechange.However,theabsorptionothisCO2hasaectedoceanchemistryandhascausedtheoceans(whichareonaverageslightlyalkaline)tobecomemoreacidic.TheaveragepHooceanicsuracewatershasbeenloweredby0.1unitssincethepre-industrialperiod.Thisrepresentsa30%increaseinhydrogenionactivity.Hydrogenionsattackcarbonateionswhicharethebuildingblocksneededbymanymarineorganisms,suchascoralsandshellfsh,toproducetheirskeletons,shellsandotherhardstructures.Thislossocarbonateionsproducelowersaturationlevelsorthecarbonateminerals,aragoniteandcalcite,whichareusedinmanyshellsandskeletons.Carbonateionconcentrationsarenowlowerthanatanyothertimeduringthelast800000years.

GlobalatmosphericCO 2concentrationsarenowat387ppm.IcurrenttrendsinCO 2emissionscontinue,modelprojectionssuggestthatbymid-centuryCO 2concentrationswillbemorethandoublepre-industriallevelsandtheoceanswillbemoreacidicthantheyhavebeenortensomillionsoyears.Thecurrentrateochangeismuchmorerapidthanduringanyeventoverthelast65millionyears.Thesechangesinoceanchemistryareirreversibleormanythousandsoyears,andthe

biologicalconsequencescouldlastmuchlonger.

2. Environmental damage rom ocean acidifcation

Oceanacidifcationimpactsonmarineliewilldependontherateandmagnitudeochangesinoceanchemistryandbiologicalresponses.Whiletheoceanchemistrychangesarepredictablewithhighcertainty,ourunderstandingotheimpactsisstilldeveloping.Nevertheless,thereisstrongevidenceemergingorarangeobiologicaleectsandchangesinthemarinebiogeochemicalprocessesthataectthecarboncycle.Thelong-termconsequencesothisaredifculttopredict.

Impactsarealreadybeingobservedinthepolarandtropicalregions.Coralcalcifcationrateshavedeclinedinrecentdecades,althoughattributingcausesortheseimpactsamongmultipledrivers(acidifcation,warming,pollution,etc.)isachallenge.FundamentalecologicaloceanprocesseswillbeaectedasmanymarineorganismsdependdirectlyorindirectlyoncalciumcarbonatesaturatedwatersandareadaptedtocurrentlevelsoseawaterpHorphysiologicalandmetabolicprocessessuchascalcifcation,growthandreproduction.ThepHchangesexpectedwillexceedtheseasonalandregional

variationscurrentlyexperiencednaturally.

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Oceanacidifcationisaglobalissue.However,changesinoceanchemistrywillberegionallyvariablewithsomeregionsaectedmorerapidlythanothers.ThehighCO 2watersinpolarandupwellingregionssuchastheeasternPacifcandBeringSeaorexample,willexperiencelowpHmorerapidlythanotherregions.Tropicalwaters,suchasthosearoundtheGreatBarrierReewillalsoexperiencerapiddeclinesinthecarbonateionsimportantorcoralreeconstruction.Accordingtorecentmodelprojectionsalmostalltropicalandsub-tropicalcoralreesweresurroundedbywatersavourabletocoralgrowthbeoretheindustrialrevolution.IatmosphericCO 2isstabilizedat450ppm,onlyaverysmallraction(~8%)oexistingtropicalandsubtropicalcoralreeswillbesurroundedbysuchwater,andat550ppm,coralreesmaybedissolvingglobally.Coldwatercoralsarealsovulnerableandarelikelytobeaectedbeoretheyhaveevenbeenullyexplored.By2100,ithasbeenestimatedthat70%willbeinwatersunavourableorgrowth.

Inthepolarregions,modelprojectionsusingcurrentCO 2emissionratessuggestthatpartsotheSouthernOceanwillbeundersaturatedoraragoniteby2050.Aragoniteundersaturationisprojectedor10%oArcticwatersbyaround2020,andby2060,80%owaterswillbeundersaturatedoraragoniteandcalcite.ThismeansthewaterswillbecorrosivetoArcticcalciferssuchaspteropods,andbivalvessuchasclams,whichplayakeyroleinArcticoodwebs.

Theoceanchemistrychangesprojectedwillexceedtherangeonaturalvariability,whichislikelytobetoorapidormanyspeciestoadaptto.Manycoastalanimalsandgroupsophytoplanktonandzooplanktonmaybedirectlyaectedwithimplicationsorfsh,marinemammalsandtheothergroupsthatdependonthemorood.IncreasedCO 2maybeparticularlystressulororganismswithhighmetabolicratessuchassquid.Theimpactsothesechangesonoceanicecosystemsandtheservicestheyprovide,orexampleinfsheries,coastalprotection,tourism,carbonsequestrationandclimateregulation,cannotyetbeestimatedaccuratelybuttheyarepotentiallylarge.

Althoughsomespeciesmaybeneft,mostareadaptedtocurrentconditionsandtheimpactsonoceanbiologicaldiversityandecosystemunctioningwilllikelybesevere.AnalysisopasteventsinEarthsgeologichistorysuggeststhatchemicalrecoverywilltaketensothousandsoyearswhiletherecoveryoecosystemunctionandbiologicaldiversitycantake

muchlonger.

4. Mitigation

Oceanacidifcationisirreversibleduringourlietimesandthoseomanygenerationstocome.Tominimisetheriskotheselarge-scaleandlong-termchangestotheoceanstheincreaseinatmosphericCO 2mustbecurbedbyreducingemissionsromhumanactivities.

RecentscenariostudieshaveestimatedthatstabilisationoatmosphericCO 2concentrationsat550ppmwillproduceenoughacidifcationtobedisastrousorsensitiveoceanicecosystemsinmanypartsotheworld.Evenat450ppm,morethan10%otheworldsoceanswillbeimpactedincludinglargepartsotheSouthern,NorthPacifc,andArcticoceans.

Mitigationapproachessuchasaddingchemicalstocountertheeectsoacidifcationarelikelytobeexpensive,onlypartlyeectiveandonlyataverylocalscale,andmayposeadditionalunanticipatedriskstothemarineenvironment.Therehasbeenverylittleresearchontheeasibilityandimpactsotheseapproaches.Substantialresearchisneededbeorethesetechniquescouldbeapplied.

5. Conclusions and recommendations

OceanacidifcationisadirectconsequenceoincreasingatmosphericCO 2concentrations.Toavoidsubstantialdamagetooceanecosystems,deepandrapidreductionsoglobalCO 2emissionsbyatleast50%by2050,andmuchmorethereaterareneeded.

We,theacademiesoscienceworkingthroughtheInterAcademyPanelonInternationalIssues(IAP),callonworldleadersto:

AcknowledgethatoceanacidifcationisadirectandrealconsequenceoincreasingatmosphericCO 2concentrations,isalreadyhavinganeectatcurrentconcentrations,andislikelytocausegraveharmtoimportantmarineecosystemsasCO2concentrationsreach450ppmandabove;

RecognisethatreducingthebuildupoCO2intheatmosphereistheonlypracticablesolutiontomitigatingocean

acidifcation;WithinthecontextotheUNFCCCnegotiationsintherunuptoCopenhagen2009,recognisethedirectthreatsposedbyincreasingatmosphericCO 2emissionstotheoceansandthereoresociety,andtakeactiontomitigatethisthreat;

ImplementactiontoreduceglobalCO2emissionsbyatleast50%o1990levelsby2050andcontinuetoreducethemthereater;

Reinvigorateactiontoreducestressors,suchasoverfshingandpollution,onmarineecosystemstoincreaseresiliencetooceanacidifcation.

Theollowingacademieshaveendorsedthisstatement.

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TWAS,theacademyosciencesorthedevelopingworld

AlbanianAcademyoSciences

NationalAcademyoExact,PhysicalandNaturalSciences,Argentina

AustralianAcademyoScience

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TheRoyalAcademiesorScienceandtheArtsoBelgium

BrazilianAcademyoSciences

BulgarianAcademyoSciences

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RSC:TheAcademiesoArts,HumanitiesandSciencesoCanada

AcademiaChilenadeCiencias

ChineseAcademyoSciences

ColombianAcademyoExact,PhysicalandNaturalSciences

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AcademyoSciencesotheCzechRepublic

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AcademyoScientifcResearchandTechnology,Egypt

TheDelegationotheFinnishAcademiesoScienceandLetters

AcadmiedesSciences,France

GeorgianAcademyoSciences

UnionderDeutschenAkademienderWissenschaten

DeutscheAkademiederNaturorscherLeopoldina

TheAcademyoAthens

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IndianNationalScienceAcademy

IndonesianAcademyoSciences

AcademyoSciencesotheIslamicRepublicoIran

RoyalIrishAcademy

IsraelAcademyoSciencesandHumanities

AccademiaNazionaledeiLincei

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