Post on 08-Jul-2020
December 2019
Thedangersofbluecarbonoffsets:fromhotairtohotwater?December 2019
Thedangersofbluecarbonoffsets:fromhotairtohotwater?December 2019
Briefing by Climate Analytics Authors: Claire Fyson, Carl-Friedrich Schleussner, Bill Hare
Cover image Mangroves in Banda Aceh, Indonesia Photo by Mokhamad Edliadi/CIFOR
Thedangersofbluecarbonoffsets:fromhotairtohotwater? 1
The dangers of blue carbon offsets: from hot air to hot water? December2019
Table of Contents
Keymessages............................................................................................................................2
Whatisbluecarbon?................................................................................................................4
Whataretherisksofusingbluecarbontooffsetemissions?...................................................4
Uncertainties......................................................................................................................................4
Impacts...............................................................................................................................................6
Offsettingandcarbontransfers................................................................................................9
LessonslearnedfromLULUCFaccounting..............................................................................10
Whatarethealternatives?.....................................................................................................10
References...............................................................................................................................12
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TheissueAstheinterestinusingnature-basedsolutionstomitigateclimatechangegrows,‘bluecarbon,’whichmeanscarbonsequesteredincoastalecosystems,isalsogarneringattention.AnumberofcountrieshaveproposedincludingbluecarbonintheirNationallyDeterminedContributions(NDCs),andthereisgrowinginterestamongsomegovernmentsandfossilfuelcompaniesinbluecarbonasanoffsetmechanism.Thisbriefingunpacksthekeychallengesandrisksassociatedwiththebluecarbonconceptbyconsideringthreekeyquestions.Whatistherealpotentialofbluecarbonasamitigationmeasure?Towhatextentiscarbonstorageincoastalecosystemsthreatenedbycurrentandfutureclimateimpacts?Andisthereadangerthatfocusonbluecarboncoulddetractfromreducingemissionsfromfossilfueluse?
Keymessages
• Usingbluecarbontoachievenationalmitigationtargetsrisksdilutingmitigationambitioninothersectors,whichcouldjeopardiseourabilitytolimitwarmingto1.5°C.Bluecarbonmustnotbeareplacementforrapidemissionsreductionsinothersectors.
• Theclimateeffectsofcarbonstoredinnaturalecosystemsandcarbonemissions
fromfossilfuelsarenotequivalent.Thismeansanyattemptstomeasureandsettargetsforcarbonsequestrationincoastalecosystemsshouldbekeptseparatefromemissionstargetsinothersectors.Lessonsfromaccountingforcarbonflowsinlanduse,landusechangeandforestry(LULUCF)haveshownthatintegratingnature-basedmitigationoffsetsundernationalmitigationtargetscreatesloopholes,hotair,andmeasurement,reportingandverification(MRV)challenges.
• Underpresentreportingandaccountingarrangementslossesfromextremeevents
andclimaticdisturbancesdonothavetobecountedbygovernmentsasemissions.Forbluecarbon,thiswouldmeanthatthelossesofcarbonfrommarineheatwaves,sealevelriseextremeeventsormultiplestressorswouldnotberecordedinnationalemissionsaccounts,eventhoughthepriorstorageofcarboncouldhavebeencountedasasinktowardsclimatetargets.Recentdie-backofcoastalecosystemsduringheatwaves(e.g.inSharkBay,Australia)haveillustratedhowsignificantthelossesofcarboncanbe.
• Focusingontheclimatesequestrationcomponentofcoastalecosystemswithina
mitigationcontextisalsoproblematicbecausetheirpotentialtoreduceemissionsanddrawdownCO2fromtheatmosphereishighlyuncertainandtoosmalltobeaneffectivemitigationstrategy.TheIPCCfoundthatcoastal‘bluecarbon’ecosystemshavealimitedglobalsequestrationpotentialofabout0.5%ofpresentdayemissionsannually(SROCC,IPCC2019).
• Ecosystemrestorationmayonlyprovidebenefitsifglobalemissionsremainlow.The
vulnerabilityofcoastalecosystemstoclimatechangeimpactsmeansthattheeffectivenesswithwhichtheydrawdowncarbonandthepermanenceoftheir
Thedangersofbluecarbonoffsets:fromhotairtohotwater? 3
carbonstoragemaybejeopardisedunderthelevelsofwarmingandsealevelriseimpliedbythecurrentsetofemissionreductioncommitments(NationallyDeterminedContributionsorNDCs).
• AccordingtotheIPCC,exceeding1.5°Cwouldleadtothenear-completelossof
tropicalcorals,andwarmingof3°Cormore–wherecurrentNDCsaretakingus–wouldleadtohightoveryhighrisksformanycoastalecosystems(includingseagrass,saltmarshesandkelpforests)(SROCCIPCC2019).
• Itisessentialtopreventthedegradationofcoastalecosystems,butcarbon
sequestrationisnotnecessarilythemostvaluableservicetheseecosystemsprovide.Thewealthofpotentialco-benefitsfromcoastalecosystemconservationandrestoration,beyondcarbonsequestration,arejustificationenoughforschemestoincentivisetheirprotection.Additionally,therearesubstantialcapacityconstraintsforthemeasurementofecosystem-relatedcarbonfluxesinmanydevelopingcountries.
• Insummary,thescienceisveryclear:protectingcoastalecosystemsandthevaluable
servicestheyprovide–includinginadaptation–requiresrapidemissionsreductionsinallsectorstolimitwarmingto1.5°C.Highuncertaintiesandimpermanenceposesignificantriskstotheuseofbluecarbonremovalsasanoffsetforotheremissions(e.g.naturalgasemissions)remaininghigh,ortheirtransferintheParisAgreement’smarketmechanisms.Treatingnature-basedmitigationasequivalenttoanyotherformofmitigationcouldhavedangerousconsequencesfortheecosystemsthatsuchmeasureswouldseektoprotect.
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Whatisbluecarbon?Bluecarbonreferstothecarbonsequesteredincoastalecosystems–namelymangroves,seagrassesandsaltmarshes1.Deforestationanddegradationofmangrovesandothercoastalecosystemsisprogressingatanalarmingrate.AccordingtotheIPCC,“nearly50%ofcoastalwetlandshavebeenlostoverthelast100years,asaresultofthecombinedeffectsoflocalisedhumanpressures,sealevelrise,warmingandextremeclimateevents(highconfidence)”(IPCC2019).Estimatesofthetotalamountofcarbonstoredinthesenaturalecosystemsgloballyarehighlyuncertain,asareestimatesofthecarbonsequesteredeachyearthroughnaturalprocessesandthepotentialforbluecarbontocontributetomitigation.TheIPCC’sassessmentinitsSROCCfoundatheoreticalmaximumpotentialof2%ofcurrentglobalemissionspotential,whichdropsto~0.2GtCO2/yr(0.05GtC/yr;onlyabout0.5%ofcurrentglobalemissions)ifcostconsiderationsareconsidered.AccordingtotheSROCC,eventhismagnitudewouldrequireascaleofecosystemrestorationthatwouldbechallengingbecauseofthesemi-permanentandgoingnatureofmostcoastallandusechanges.Thecoastalecosystemsassociatedwithbluecarbonprovidenumerousothercrucialservices,bothforpeopleandforbiodiversity.Theneedtoconserveandprotectthesevitalecosystemsisgarneringincreasedattentionbutthishasledtodiscussionsovertheuseofbluecarbontoincentivisesuchefforts.However,afocusonthecarbonsequesteredincoastalareasrisksdistractingfromtheneedtourgentlymitigateemissionsinothersectors,aswellastheneedtopreservethelife-supportingecosystemservicesthatcoastalecosystemsprovide.
Whataretherisksofusingbluecarbontooffsetemissions?Therearethreefundamentalproblemswithusingmitigationthroughlandorocean-basednaturalsystemstooffsetCO2emissions:uncertainties,climatechangeimpacts,andtheriskofoffsetting.Thesearedescribedbelow.
Uncertainties Theuncertaintiesinthemeasurementofcarbonflowsinthehighlyvariableenvironmentinthecoastalzonearemuchhigherthantheuncertaintiesinemissionsinothersectors.Therearealsouncertaintiesoverthepermanenceofocean-basedmitigation,andtheriskofleakageofemissionsthroughcoastalchangeelsewhere.Theseuncertaintiesmeanthatmitigationusingcoastalecosystemscannotbetreatedlike-for-likewithotherformsofmitigation.
1CarbonsequestrationintheopenoceanisnottypicallyconsideredaBlueCarbonoption.Intheopenocean,human
Thedangersofbluecarbonoffsets:fromhotairtohotwater? 5
1. Changesovertime
Tropicalmangroveforestschangeovertime.Mangrovesarenon-linearsystemsthatarenotinequilibrium,astheyhaveadaptedtogrowoncontinuallyevolvingshorelines.Theamountofcarbonsequesteredbymangrovesandothercoastalecosystemsvariessubstantiallybetweenlocationsandasafunctionoftime.Whilemangrovesareoftendescribedasbeingfarmoreintensecarbonsinksthantropicalforests,somemangrovesystemsmaynotactuallyaccumulateanycarbon.Forexample,asurveyof17Australianseagrasshabitatsrevealedan18-folddifferenceinthecarbonstored(Laveryetal2013).
2. Measurementuncertainties
Themeasurementofcarbonstorageisdifficultandshouldbeinterpretedcautiously.Someoftheprocessesinvolvedindrawingdowncarbonintosedimentsarehighlysitespecific,orarestillnotwellaccountedfor.Adameetal.(2017)comparedestimatesofmangroverootbiomasscalculatedusingallometricequationswithvaluesmeasuredinthefieldandfoundfieldmeasurementstobeonaverage40%smaller(withsomesamplesshowingadifferenceofover1000%).Anotherchallengeisthatanumberofprocessesincoastalsystemsarepoorlyunderstood.Forexample,thefateofcarbononceithasbeendepositedinacoastalareaisstillunknown(Atwoodetal2017).
ScientiststrytoassesshowcarbonsequestrationofIndonesia'smangroveforests.PhotobyCenterforInternationalForestryResearch(CIFOR)
Itisalsoverydifficulttodeterminewhichemissionsandremovalsarenaturalandwhichareanthropogenic.Onlyanthropogenicemissionsandremovalsshouldbeincludedinmitigationtargets.
Thesemeasurementchallengesareaparticularproblemforthosedevelopingcountrieswithlimitedcapacitiesformonitoringandreportingemissionsandremovals,leadingtodatagapsandevengreateruncertainties.
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3. CO2effects
MangrovesandseagrassesmayexperienceenhancedproductivityduetohigherCO2levels(IPCCAR5).Distinguishingthiseffectfromhumaninterventionstoenhanceproductivityandthuscarbonstoragewillbedifficult.
4. Permanenceandleakage
Aswithotherland-basedcarbonsequestration,ensuringpermanenceandpreventingleakageisverydifficult.Climatechangeimpactsoncoastalecosystemscanleadtoareversalofcarbonsequestrationinthefuture(seebelow).Inaddition,conservationofoneareamaydisplacedeforestationordegradationtoanotherarea,leadingtoleakage,andensuringthelongevityofcarbonstoredinconservedorrestoredmangrovesrequiresastrongMRVsystem(Murrayetal2009).
Impacts TherecentlyreleasedIPCCSpecialReportonOceansandCryosphereinaChangingClimatehasbroughtnewevidenceonthedevastatingimpactsthatfutureclimatechangecouldhaveoncoastalandoceanecosystems,pointingtotheimportanceofprotectingtheoceansbyenhancingambitionacrossallsectors.AccordingtotheIPCC’sSROCC,exceeding1.5°Cwouldleadtothenear-completelossoftropicalcorals,andwarmingof3°Cormore–wherecurrentnationallydeterminedcontributions(NDCs)aretakingus–wouldleadtohightoveryhighrisksformanycoastalecosystems(includingseagrass,kelpforestsandsaltmarshes).Onlylimitingwarmingto1.5°Ccanpreventlandandoceanecosystemsfromexperiencinghightoveryhighlevelsofrisk.
Suchimpactscouldaffectcarbonstorage(IPCCAR5(2013)).TheIPCC’sSROCChighlightedtheimplicationsoftheseimpactsforcarbonsequestration:“Underhighemissionscenarios,sealevelriseandwarmingareexpectedtoreducecarbonsequestrationbyvegetatedcoastalecosystems(mediumconfidence)”(Chapter5,SROCC)
Emissionsthatresultfromsuchreversalsmaygounaccountedfor,orremovalsmaybeoverestimatedorreversed.Theregionalvariationinclimateimpacts,andtheiraccelerationinfrequencyandintensitywithfuturewarming,willmakedesigningarobustsystemforaccountingfornaturaldisturbancesverydifficult.
1. Sealevelrise
Researchhasshownthatcoastalecosystemsinsomeregionsarevulnerabletosealevelrise.Ifsedimentsupplyissufficientformangrovestogrowinpacewithsealevelthenecosystemscancontinuetosurviveandtosequestercarbon,butinmanyregionssedimentsupplyisnotsufficient(Lovelocketal.2015).Forexample,intheIndo-Pacific–hometooverhalfoftheworld’smangroveforests–sedimentdeliveryisdeclining,largelyduetohumanactivity,e.g.dammingrivers.Mangroveforestsatsiteswithlowsedimentsupplyandlowtidalrange–suchastheGulfofThailandandtheSolomonIslands–areparticularlyvulnerable,andcouldbesubmergedby2070underevenalowlevelofsealevelrise(Lovelocketal.2015).
Thedangersofbluecarbonoffsets:fromhotairtohotwater? 7
MangrovesinMalaita,SolomonIslands.PhotobyWadeFairley
TheIPCCSROCCfoundthatmangroveandmarshrestorationwouldonlybeeffectiveofuptoratesof0.5-1cmlocalsealevelriseperyear.Theselevelswillbefarexceededunderahighemissionsscenario(theSROCCgivesabestestimateof1.5cmglobalsealevelriseby2100underaRCP8.5scenario),andunderscenariosclosetocurrentNDCambitionlevels,sealevelrisewillalsolikelyexceed1cmperyeartowardstheendofthecentury(Nauelsetal2017).OnlyunderaParisAgreementscenariomayratesofglobalsealevelrisestaybelow0.5cmperyear(IPCC2019).However,evenundersuchascenariosomesystemsmaystillcomeunderpressurebecauseregionalsealevelriseinmanytropicalregionswillbewellabovetheglobalaverage.
TheIPCC’sSROCCfoundthat:“Globally,20–90%ofcurrentcoastalwetlandsareprojectedtobelostby2100,dependingonprojectedsealevelrise,regionaldifferencesandwetlandtypes”(B6.2,SROCCSPM).Italsostatesthat“Underhighemissionscenarios,sealevelriseandwarmingareexpectedtoreducecarbonsequestrationbyvegetatedcoastalecosystems(mediumconfidence)”(Chapter5,SROCC).
ExchangeatSBSTIPCCSROCCSpecialEvent,COP25Madrid,5December2019
Fijiintervention:
Wehavelearnedthatimpactsonoceanecosystemsarealreadyveryconcerning.TheIPCCSROCCassessedthatcoastalecosystemswithadaptationpotentialfaceclearefficiencylimitsunderongoingclimatechange.Mangrovesandsaltmarshes,forexample,wouldonlyprovideecosystem-basedadaptationpotentialbelow1cmofglobalmeansea-levelriseperyear.CouldtheSROCCauthorspleaseclarifywhichscenarioswouldallowsea-levelriseratestobelimitedtobelow1cmbytheendofthe21stcentury?
IPCCWGICo-Chairresponse(basedonsessionnotes):
Forascenariowithmeanprojectedwarmingof1.6°Cbytheendofthe21stcentury(RCP2.6),theprojectedaverageglobalsea-levelriserateis4mmperyear,withanupperlikelyrangeupto6mm,forawarmingofaround2.5°Cby2100,theprojectedaverageglobalsea-levelriserateshowsamedianvalue7mmperyear,withanupperlikelyrangeof9mmperyear,whichiscloseto1cmperyear.Currentevidencethereforesuggeststhatwarmingneedstobelessthanaround2.5°Cby2100tolimitglobalsea-levelriseratestolessthan1cmperyear.
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2. SealevelextremesandfluctuationTheIPCCSROCChasfoundwithhighconfidencethatextremesealeveleventsthatarehistoricallyrare(oncepercenturyintherecentpast)areprojectedtooccuratleastannuallyinmanylocationsby2050,especiallyintropicalregions.Sucheventscanbeverydamagingforcoastalecosystems.
Insomeregionssealevelcanfluctuatewithchangesinrainfall.Forexample,theIndo-PacificexperienceslowrainfallandlowsealevelsduringElNiño,andthiscanleadtosalinizationofthesoilandmangrovemortality(Lovelocketal2017).IntensificationofENSOunderclimatechangeandassociatedfluctuationsinsealevelmayleadtomangrovedegradationandcarbonrelease,andmayfurtherincreasemangrovevulnerabilitytootherimpactsofclimatechange,pollution,andotherhumaninfluences(Lovelocketal2017).
3. Oceanwarming
TheIPCCSROCChasfoundthat“Marineheatwaveshaveverylikelydoubledinfrequencysince1982andareincreasinginintensity(veryhighconfidence).”2
Itfurtherstates:“Itisverylikelythatbetween84–90%ofmarineheatwavesthatoccurredbetween2006and2015areattributabletotheanthropogenictemperatureincrease.”3Suchclimate-changeattributableoceanheatwaveshavealreadyhadsevereimpactsoncoastalecosystems.
Forexample,forafour-monthperiodin2010/2011seatemperaturesinwesternAustraliawere2-4°Caboveaverage,damaging36%ofseagrassbedsintheSharkBayarea(Arias-Ortizetal2018).Twoyearslater,theseecosystemshadonlypartiallyrecovered(Nowickietal2017).Recentresearchsuggeststhat2–9MtCO2couldhavebeenreleasedduringthethreeyearsfollowingtheheatwave,increasingAustralia’sland-usechangeemissionsby4-21%peryear(Arias-Ortizetal2018).
SharkBayseagrassexamplebefore2011heatwave(L)andstudysitein2013(R).CreditSharkBayEcosystemResearchProject.SharkBay,WesternAustralia.Photo:JoanCosta
2https://www.ipcc.ch/srocc/headline-statements/3IPCCSROCCSPMParaA.2.3,https://www.ipcc.ch/srocc/chapter/summary-for-policymakers/
Thedangersofbluecarbonoffsets:fromhotairtohotwater? 9
Suchwarmingeventsareprojectedtobecomemorecommoninthefuture,whichisparticularlyconcerninggiventheslowrecoveryratesofmanycoastalecosystemsandthepotentialforadverseclimatechangefeedbacksduetocarbonrelease.
4. Interactingstressors
Manycoastalspeciesareabletocopewithhighlyvariableenvironments,buttheinteractionsofmultiplestressorscanamplifynegativeimpactsanddriveecosystemsintoalternativestates.Forexample,onestudyfoundthatamarineheatwaveincombinationwithafloodingonland,leadingtosedimentdischargeandhighwaterturbidityinthenear-shoremarineenvironmentinwesternAustralia,resultedinlossofseagrassbiomassbothaboveandbelowground,andultimatelyreducedtheresilienceoftheecosystemtofuturedisturbance(Fraseretal2014).
5. Impactsoncarbonsequestration
IncreasedCO2,warmertemperaturesandmoderateincreasesinsealevelcanincreaseratesofplantproductivityandcarbonsequestration.However,thesesamedriverscanalsoacttoreducethecarbonpool,forexample,warmertemperaturesandincreasedCO2canalsoincreasedecayrates,loweringtherateofcarbonsequestration.Howthesefactorswillplayoutinthefuture,especiallyinthecontextofthenegativeimpactsoutlinedabove,isveryuncertain.
OffsettingandcarbontransfersAkeyfindingoftheseIPCC’sSROCCisthatnature-basedmitigationmustnotbeareplacementforrapidlyacceleratingemissionsreductionsinothersectors:“Thepotentialclimaticbenefitsofbluecarbonecosystemscanonlybeaverymodestadditionto,andnotareplacementfor,theveryrapidreductionofgreenhousegasemissions.”(SROCCChapter5,executivesummary).Offsettingreducestheambitionofmitigationinothersectors,andcanleadtolock-intocarbonintensiveinfrastructure.Previouslyinsufficientmitigationactionmeansthatasubstantialvolumeofnegativeemissionswillbeneededinadditiontoambitiousactioninallothersectors,sothereisnospaceinemissionspathwaysfortheuseofmitigationfromnature-basedsystemstooffsetemissionsinothersectors,unlessthoseemissionsareprohibitivelyexpensivetomitigate.
Theuncertaintiesandvulnerabilitiesassociatedwithbluecarbonmeanthatitwillnotworktodeploybluecarbonasanoffsetforotheremissionsthatremainhigh.Anymovementofcarboncreditsanddebitsbetweennature-basedsystemsandothersectorsrisksleakingthehighuncertaintiesassociatedwithbluecarbontomitigationinothersectors,makingitdifficulttomonitorprogressandtoensurethatactionisinlinewiththeParisAgreement.Furthermore,theIPCCSROCCnotesthatecosystemrestorationmayonlyprovidebenefitsforlesssensitivesystemsandifglobalemissionsremainlow.
Thesehighuncertaintiesandvulnerabilitiesposesignificantriskstothetransferofbluecarbonremovalsbetweencountriesviamarketmechanisms.TherulesfortheParisAgreementmarketmechanismsarestillbeingagreed,andifremovalscanbetradedunder
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thesemechanismswithinsufficientsafeguardsinplacetoaddressimpermanenceanduncertainties,thiscouldunderminethecredibilityofthemarketssystem.
LessonslearnedfromLULUCFaccountingAnumberofrelevantlessonshavebeenlearnedfromtheland-use,land-usechangeandforestry(LULUCF)sector:• ThedevelopmentofaccountingrulesfortheLULUCFsectorundertheKyotoProtocolallowedgovernmentstodevelopcomplicatedrules,whoseimplicationsarebeyondtheunderstandingofmostpolicymakers,scientistsandmembersofcivilsociety.Theseruleshaveenabledsomeemissionstogouncountedtowardsnationalemissionstargets,creating‘hotair’thatunderminestheneedforrapidemissionsreductions.
• Forexample,underArticle3.7anycountrythathadland-useemissionsinthebaseyear(1990)canincludetheseintheirreferenceyearemissionswhencalculatingtheirreductiontarget.Anydecreasesinemissionsexcludingland-userelativetothebaseyearincludingland-useemissionsareawarded.Forexample,asubstantialdecreaseindeforestationratessince1990isallowingAustraliatocomplywithits2020Kyototargetwhenaccountingrulesareapplied,despiteacontinuedincreaseinfossilemissions(ClimateActionTracker2015,2017).
• NowcountriesvarywidelyinhowtheyincorporatetheLULUCFsectorintheirNDCs,whichleadstoconsiderableuncertaintyinemissionsreductiontargets(GrassiandDentener2015,FysonandJeffery2019),particularlywheregovernmentshavechosentoincludeLULUCFintheiroverallemissionstargetwithoutspecifyingitscontribution.TheinclusionofbluecarbonintheNDCspresentssimilarchallenges.
• Lossesfromextremeeventsandclimaticdisturbancesdonotneedtobecountedinnationalemissionsaccounts.Underpresentreportingandaccountingarrangementslossesofcarbonfrommarineheatwaves(asatSharkBay),sealevelriseextremeeventsormultiplestressors(asinthemassivemangrovediebackinAustralia’sGulfofCarpentaria)couldbeexcludedfromnationalemissionsreports,eventhoughthepriorstorageofcarboncouldhavebeencountedasasinkandcountedtowardsclimatetargets.
Whatarethealternatives?Coastalecosystemsarethreatenedbyanumberofstressors:coastalinfrastructure,tourism,agriculture,aquaculture,damdevelopment,pollution,andoverfishing,amongothersaswellasclimatechange.Therapidrateatwhichtheyarebeingdegradedisparticularlyconcerningbecausemangrovesandothercoastalecosystemsarevitalforcoastalcommunities,providingessentialfoodandresourcesaswellasbuildingresiliencetoclimatechangeimpactsthroughcoastalprotectionanderosionreduction.Itisthesebenefitsofcoastalecosystemrestorationthatshoulddriveconservationandrestorationefforts.
Thedangersofbluecarbonoffsets:fromhotairtohotwater? 11
TheIPCC’sSROCCpointedspecificallytotheadaptationbenefitsthatcoastalecosystemsprovidetolow-lyingcoastalregions,includingSmallIslandDevelopingStates.However,thereporthighlightedthatecosystem-basedadaptationisonlyaneffectiveoptionunderthelowestlevelsofwarming.Therearelimitstotheeffectivenessofcoastalecosystem-basedadaptationathigherlevelsofwarming.Forexample,coralreefconservationandrestorationmaybeineffectiveifwarmingexceeds1.5°C;conservationandrestorationofwetlandssuchasmarshesandmangroveshasdecreasedeffectivenessat2°C.At2°Candabove,therewillbeanincreasingneedforhardcoastalprotectioninfrastructure,andagreaterriskofcoastalcommunityrelocation.Thesefindingsfurtheramplifytheneedtoreduceemissionsinlinewiththe1.5°CwarminglimitoftheParisAgreement,whichmustcomealongsideeffortstoconserveandrestorecoastalecosystems.Itisdifficulttogenerateeconomicincentivesforconservationofcoastalecosystemsbecausemanyoftheservicesthattheyprovidedonothaveamarketprice,andoftendecisionsthatresultintheirdegradationaremadebybodiesforwhomthevalueofmangrovesisnon-existent(Mukherjeeetal2014).Toprovideanincentiveforthepreservationandsustainableuseoftheseecosystems,PaymentforEcosystemServices(PES)schemescanbeusedtoplaceavalueonthoseservicesthatarevaluabletolocalcommunities.Thewealthofservicesprovidedbymangrovesandothercoastalecosystemmakesthemwell-suitedforsuchschemes.OneestimatefortheannualeconomicvalueofmangrovelossfromaquaculturecametoUS$4-17billion(Mukherjeeetal2014),andthislikelyunderestimatedthevaluetolocalpopulationsofanumberofbenefits.Notably,thesamestudyshowedthatcarbonsequestrationdoesnotrankhighlyintermsofeconomicvalueorexpert-basedvaluation.Numerousotherecosystemservicesaremoreimportantforlocalcommunities:food,livelihoods,constructionmaterialsandcoastalprotectionprovideessentiallifesupportservices,anditistheseservicesthatshouldbedrivingtheprotectionofcoastalecosystems.
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