Noah's Ark Conservation Will Not Preserve Threatened Ecological Communities under Climate ...

18 Pages·2015·0.67 MB·English

RESEARCHARTICLE
’
Noah s Ark Conservation Will Not Preserve
Threatened Ecological Communities under
Climate Change
RebeccaMaryBernadetteHarris1*,OberonCarter2,LouiseGilfedder2,Luciana
LauraPorfirio3,GregLee1,NathanielLeeBindoff1,4,5
1 AntarcticClimateandEcosystemsCooperativeResearchCentre(ACECRC),UniversityofTasmania,
Hobart,Australia,2 ResourceManagementandConservationDivision,DepartmentofPrimaryIndustries,
Parks,Water&Environment,Hobart,Australia,3 FennerSchoolofEnvironmentandSociety,Australian
a11111
NationalUniversity,Canberra,Australia,4 InstituteforMarineandAntarcticStudies(IMAS),Universityof
Tasmania,Hobart,Australia,5 ARCCentreofExcellenceforClimateSystemsScience,UniversityofNew
SouthWales,Sydney,Australia
* [email protected]
Abstract
OPENACCESS
Citation:HarrisRMB,CarterO,GilfedderL,Porfirio
Background
LL,LeeG,BindoffNL(2015)Noah’sArk
ConservationWillNotPreserveThreatened Effectiveconservationofthreatenedecologicalcommunitiesrequiresknowledgeofwhere
EcologicalCommunitiesunderClimateChange.
climaticallysuitablehabitatislikelytopersistintothefuture.Weusethecriticallyendan-
PLoSONE10(4):e0124014.doi:10.1371/journal.
geredLowlandGrasslandcommunityofTasmania,Australiaasacasestudytoidentifyop-
pone.0124014
tionsformanagementincaseswherefutureclimaticconditionsbecomeunsuitableforthe
AcademicEditor:KamalBawa,Universityof
currentthreatenedcommunity.
Massachusetts,UNITEDSTATES
Received:October19,2014
Methods
Accepted:March9,2015
WemodelcurrentandfutureclimaticsuitabilityfortheLowlandThemedaandtheLowland
Published:April16,2015 PoaGrasslandcommunities,whichmakeupthelistedecologicalcommunity.Wealso
Copyright:©2015Harrisetal.Thisisanopen modelclimaticsuitabilityforthestructurallydominantgrassspeciesofthesecommunities,
accessarticledistributedunderthetermsofthe andforcloselyrelatedgrasslandandwoodlandcommunities.Weuseadynamicallydown-
CreativeCommonsAttributionLicense,whichpermits
scaledregionalclimatemodelderivedfromsixCMIP3globalclimatemodels,undertheA2
unrestricteduse,distribution,andreproductioninany
medium,providedtheoriginalauthorandsourceare SRESemissionsscenario.
credited.
Results
DataAvailabilityStatement:Themodelled
projectionsareavailablethroughtheTasmanian Allmodelprojectionsshowedalargereductioninclimaticallysuitableareabymid-century.
PartnershipforAdvancedComputing(TPAC)portal
Outcomesareslightlybetterifcloselyrelatedgrassycommunitiesareconsidered,butthe
(https://dl.tpac.org.au/tpacportal/).TheTasVeg
extentofsuitableareaisstillsubstantiallyreduced.Onlysmallareaswithinthecurrentdis-
vegatationlayerscanbefoundathttp://maps.thelist.
tas.gov.au/.Nootherdatawereusedintheanalyses, tributionareprojectedtoremainclimaticallysuitablebytheendofthecentury,andverylittle
whichwereproducedusingafreelyavailableSpecies ofthatareaiscurrentlyingoodcondition.
DistributionModel,MAXENT.
Funding:Thisresearchisanoutputfromthe Conclusions
LandscapesandPolicyResearchHub,whichis
Astheclimatebecomeslesssuitable,agradualchangeinthespeciescomposition,struc-
supportedthroughfundingfromtheAustralian
Government’sNationalEnvironmentalResearch tureandhabitatqualityofthegrasslandcommunitiesislikely.Conservationmanagement
PLOSONE|DOI:10.1371/journal.pone.0124014 April16,2015 1/18
ChangeinThreatenedCommunitiesunderClimateChange
Program(GrantnumberL0018856)(http://www. willneedtofocusonmaintainingdiversity,structureandfunction,ratherthanattemptingto
environment.gov.au/science/nerp).Thefundershad preservecurrentspeciescomposition.Optionsforachievingthisincludemanagingrelated
noroleinstudydesign,datacollectionandanalysis,
grasslandtypestomaintaingrasslandspeciesatthelandscape-scale,andmaximisingthe
decisiontopublish,orpreparationofthemanuscript.
resilienceofgrasslandsbyreducingfurtherfragmentation,weedinvasionandstressfrom
CompetingInterests:Theauthorshavedeclared
otherlanduses,whileacceptingthatchangeisinevitable.Attemptingtomaintainthestatus
thatnocompetinginterestsexist.
quobyconservingthecurrentstructureandcompositionofLowlandGrasslandcommuni-
tiesisunlikelytobeaviablemanagementoptioninthelongterm.
Introduction
Distributionsofspeciesandcommunitiesareshiftingduetochangingclimaticconditions
[1–4],andattemptstomaintainthestatusquointermsofspeciescompositionmaybefutilein
manyregionsoftheworld.Variabilitythroughtimeisaninherentpartofecosystembehaviour,
butconservationmanagementfrequentlyreliesonastaticviewofecosystems[5].Listedeco-
logicalcommunitiesareboundbyenvironmentallegislationthatsetsthresholdsforacceptable
condition,speciesrichnessandcomposition.Forconservationmanagementtobeeffectivein
thefuture,itwillneedtoaccommodatechangingecologicaldynamics.Optionsthatenablethe
diversity,structureandfunctionofecosystemstobemaintainedwillneedtobeidentified,rath-
erthanattemptingtopreservecurrentspeciescomposition.
TemperategrasslandsareamongthemostthreatenedvegetationtypesonEarth,sincethey
occurinthoseenvironmentsmostamenabletohumansettlementandagriculture[6].InAus-
tralia,lowlandtemperategrasslandsareanationalconservationpriority,withlessthan1%of
theiroriginalextentremaining[7].Lowlandtemperategrasslandsaredominatedbynative
grasses,withfewornoemergentwoodyspecies.Thedominantgrassesaretussock-forming,
andavarietyofsmallforbsorwildflowersandnon-tussockforminggrassesandsedgesoccur
intheinter-tussockspaces.Remnantpatchesingoodconditionarespecies-richandareimpor-
tanthabitattoadiversearrayoffloraandfauna,manyofwhicharealsolistedasvulnerable
orthreatened.
TasmanianLowlandTemperateNativeGrasslands(LNGT)arelistedasCriticallyEndan-
geredontheEnvironmentProtectionandBiodiversityConservationAct1999,theAustralian
Government’snationalenvironmentallegislation.Lessthan10%ofthenaturalextentofthis
communityremains[8]andmostisonprivately-ownedland.TheLNGTarecomprisedoftwo
mainfloristictypes,determinedbythedominantgrassspecies.TheLowlandThemedaGrass-
landcommunity(GTL)isdominatedbyThemedatriandra(Kangaroograss)andtheLowland
PoaGrasslandcommunity(GPL)isdominatedbyPoalabillardierei(Tussockgrass).Austro-
danthoniaspp.(Wallabygrass)and/orAustrostipaspp.(Speargrass)mayalsobepresent,along
withadiverseassemblageofherbsandforbs,andfewwoodyorshrubbyspecies.
NativegrasslandcommunitiesinTasmaniaareoftenrepresentedbysmall,highlyfrag-
mentedremnants,whichvarygreatlyinconditionduetopastlandusessuchasgrazing,burn-
inganduseoffertilisers.Currentconditionislikelytobeimportantforthelong-termviability
ofacommunity,withgrasslandsinbetterconditionmoreresilienttochangeintheshortterm,
andmoreadaptableinthelongterm,duetotheirgreatergenetic,floristicandstructuraldiver-
sity[9–12].
Managementofthreatenedecologicalcommunitiesrequiressomeknowledgeofwherecli-
maticallysuitablehabitatislikelytopersistintothefuture[13].Incontrasttothecommonap-
proachofmodellingchangestothedistributionofasinglespeciesofinterestunderclimate
PLOSONE|DOI:10.1371/journal.pone.0124014 April16,2015 2/18
ChangeinThreatenedCommunitiesunderClimateChange
change,wemodelthedistributionofalistedecologicalcommunityasawhole.Wheredomi-
nantspeciesarewidespread,butthecommunityhasahighlyrestricteddistribution,modelling
climaticsuitabilityforthedominantspecieswilltendtooverestimatetheextentofsuitablecli-
mateforthecommunity.Modellingtheextentofthecommunityismorelikelytocaptureim-
portantlimitingfactorsandinteractions[14].
AveragetemperaturesinTasmaniaareprojectedtoincreaseby2.6to3.3°Cbytheendof
thiscenturyunderahighemissionsscenario(A2)[15,16].Temperaturechangeisprojectedto
befairlyuniformacrossTasmania,andbroadlysimilaracrossseasons.Incontrast,totalannual
rainfallisnotprojectedtochange,buttherearesignificantchangesinthespatialpatternand
seasonalityofrainfall.Annualrainfallisprojectedtoincreaseovercoastalregions,anddecrease
inpartsofnorthwestandcentralTasmaniawherethegrasslandscurrentlyoccur.Inthese
areas,autumnrainfallisprojectedtoincreasesignificantlyafter2050,anddecreaseinspring.
Thesuitabilityoffutureclimaticconditionsfortemperategrasslandsmaythereforebeinflu-
encedbychangestoseasonalityandinteractionsbetweenclimatevariables,inadditionto
changestomeanconditions.Shiftsinthefloristics,structureandphenologyofgrasslandcom-
munities,withaconsequentlossofhabitatandchangedcompositionofspeciesassemblages,
areexpectedtooccurasadirectresponsetothechangingclimate[10].Other,indirecteffects
arelikely,includingchangesinsoilpropertiesandnutrientcycling,changestofireregimes,in-
creasedriskofweedinvasion,andchangesinlanduseandmanagement,including“drought-
proofing”throughirrigationandenterprisediversificationsuchasnewcropsandcarbon
plantings.
Thereareseveralvegetationcommunitiessimilarincompositionandgeographicextent
thatarelikelytobeimportantinthelong-termconservationoftheLNGT.Firstly,theLowland
GrasslandComplex(GCL)includesgrasslandsthatarenotclassifiedasLNGTbecausethey
haveinsufficientcoverofPoalabillardiereiorThemedatriandra.Theyhaveasignificantly
greaterextentthanLNGT,andmayplayanimportantfunctionalroleinmaintaininggrassland
speciesacrossthelandscape.GCLaremostlyderivedfrompriorclearingofnativegrassy,dry
woodlandandforestcommunitiesorfromeucalyptdiebackevents[17].Secondly,theBur-
saria-Acaciawoodlandandscrubcommunity(NBA)gradeswithLNGTbutisexcludedfrom
LNGTwhereB.spinosaexceeds30%cover.Thiscommunityhasanherb-richgrassyunder-
storeydominatedbyThemedatriandrawithemergentBursariaspinosashrubs(upto3–4m).
ThestructureofNBAisoftenanartefactoffireandgrazinghistory,andincreasedfrequency
ofburningcanpromotegrasslandvegetationandreduceshrubcover.Grasslandsformacon-
tinuumwithgrassywoodlandsdominatedbyvariousEucalyptusspecies,whichcouldbean
importantcomponentofthemanagementmatrixifmanagedtomaintainorfavourgrasslands.
Inthispaperweidentifypossibleoptionsformanagingthreatenedcommunitiesundercli-
matechange,usingtheLowlandGrasslandcommunity(LNGT)inTasmania,Australiaasa
casestudy.Firstly,wetestwhetherfutureclimateconditionsarelikelytoremainsuitablefor
thelowlandgrasslandcommunitieswhichmakeuptheLNGT(GTLandGPL),andfortheir
structurallydominantspecies.Wealsomodelcurrentandfutureclimaticsuitabilityforclosely
relatedgrassland(GCL)andwoodlandcommunities(NBA)inordertoidentifyoptionsfor
managementintheeventthatfutureclimaticconditionsbecomeunsuitableforthecurrent
lowlandgrasslandcommunity.
Methods
EthicsStatement
Noethicsapprovalorpermissionstoaccessprivateorpubliclandswererequiredforthis
study.
PLOSONE|DOI:10.1371/journal.pone.0124014 April16,2015 3/18
ChangeinThreatenedCommunitiesunderClimateChange
CommunityandSpeciesDistributionModelling
ClimaticsuitabilitywasmodelledforthetwograsslandcommunitiesthatmakeuptheLNGT,
theLowlandThemedaGrasslandcommunity(GTL)andtheLowlandPoaGrasslandcommu-
nity(GPL),aswellasrelatedgrassycommunities,theBursaria-Acaciawoodlandandscrub
community(NBA)andtheLowlandGrasslandComplex(GCL).Anunderstandingofthedis-
tributionofeachcommunity,inadditiontoitsstructurallydominantspecies,isnecessaryfor
thepracticalmanagementandconservationofalistedcommunityunderchangingconditions.
GTLandGPLweremodelledseparatelybecausetheyareexpectedtoresponddifferentlyto
changingclimatevariablesduetothedifferentphotosyntheticpathwaysemployedbytheir
structurallydominantspecies.PoalabillardiereiisaC3grass,whileThemedatriandraisaC4
grass.Ingeneral,itisexpectedthatglobalwarmingwillincreasethedominanceofC4grasses,
whichhavehigherwaterefficiency,greaterdroughttolerance,andgreaterpersistenceinwarm-
erclimatesthanC3species[18].However,theeffectofelevatedCO andcompetitiveinterac-
2
tionsbetweenC4andC3plantsunderdifferentnutrientconditionsandseasonalityarenot
wellunderstood[19,20].
Presencelocationsforeachofthegrasslandcommunitiesweregeneratedbyrandomlysam-
pling1000pointsfromwithintheexistingdistributionofeachofthecommunitytypesfrom
thestate-widedigitalvegetationmap,TASVEG3.0[21].Althoughgrasslandscoveredalarger
extentpriortoEuropeansettlementintheearly19thcentury,andpreferentialclearingmay
haveoccurredinthepastonmorefertilesoilsorareaswithfewertrees,theremaininggrass-
landsaredistributedwithinthelikelyextentoftheoriginal,sosamplingthecurrentdistribu-
tionisareasonableapproximationtotherangeofsuitableclimaticconditions.
Theclimaticsuitabilityforthetwostructurallydominantgrasses,PoalabillardiereiandThe-
medatriandra,weremodelledundercurrentandfutureclimateconditionstoassesstheextent
towhichthecompositionofthegrasslandcommunitiesmightchangeunderfutureclimate
conditions.LocalitydatafortheAustraliangeographicextentofthesespeciesweredownloaded
fromtheonlinedatabaseAtlasofLivingAustralia(http://collections.ala.org.au/public).After
excludingspatiallysuspectrecords,therewere19,313uniqueobservationsfromtheyears1770
to2014forThemedatriandra,and5,755observationsforPoalabillardiereivar.labillardierei
fromtheperiod1853to2013.
TheMaxentmodel[22]wasusedtoprojectthedistributionofclimatesuitableforthegrass-
landcommunitiesandspeciesundercurrentandfutureclimateconditions.MaxentisaSpecies
DistributionModel(SDM),orclimateenvelopemodel,whichusespresenceonlydata.SDMs
arebasedonthestatisticalrelationshipbetweenenvironmentalorclimaticvariablesandthe
current,observeddistributionofaspeciesorcommunity.Assumingthatthisrelationshipre-
mainsunchanged,thefuturedistributionofthespeciesisthenprojectedaccordingtofuture
climaticconditions.Othermodellingapproachesareavailable,includingBoostedRegression
Trees,GeneralizedLinearModelsandGeneralizedAdditiveModels,andensemblesofthese
aresometimesusedtorepresenttherangeinSDMoutputs[23–25].WechoseMaxentbecause
itishasbeenshowntoperformwellincomparisontoseveralothermodelswhentherearefew
presencerecordsavailable[26].Foreachmodelrun,tenreplicateMaxentrunswerecalculated
bycross-validationandusingdefaultvaluesforallotherparameters(e.g.regularisation).Rela-
tiveoccurrenceprobabilitiesabove0.5wereconsideredsuitable,followingPhillips&Dudík
[27].
Choiceofexplanatoryvariableshasanimportantinfluenceontheoutcomeofspeciesdistri-
butionmodels[28–31].Weusemodelsbasedonclimatevariablestoprojectchangestothe
communitiesandspecies’potentialclimatedomain.Ourresultsthereforeindicaterelativecli-
maticsuitabilityratherthanhabitatsuitability.Intheabsenceofknowledgeaboutthespecific
PLOSONE|DOI:10.1371/journal.pone.0124014 April16,2015 4/18
ChangeinThreatenedCommunitiesunderClimateChange
variableswhichdeterminegrasslanddistributionsinTasmania,weusedsaturatedmodels
basedonthefullsetofthirtyfivecommonlyusedbioclimaticvariablesandallowedMaxentto
performvariableselection.Maxenthasbeenshowntoberobusttocorrelatedvariables[32],
andavoidsover-fittingbyapplyingaregularizationpenaltyforeachtermincludedinthe
model[22,33,34].Weusedthedefaultregularizationsettings,basedonvaluesdeterminedas
optimalinempiricaltuning[27].
FutureClimateProjections
Futureclimateconditionsweretakenfromadynamicallydownscaledregionalclimatemodel,
theConformalCubicAtmosphericModel(CCAM),developedbytheCommonwealthScien-
tificandIndustrialResearchOrganisation(CSIRO),Australia.SixCMIP3globalclimatemod-
els(ECHAM5/MPI-OM,GFDL-CM2.0,GFDL-CM2.1,UKMO-HadCM3,CSIROMk3.5and
MIROC3.2(medres))weredownscaledto~10kmresolutionbytheClimateFuturesforTasma-
niaproject.Thesemodelswerechosenbecausetheyrepresentcurrentsouth-eastAustraliancli-
matemeansandvariabilitywell[35],andcoverthespreadofprojectedrainfallchangein
southeastAustraliapresentintheCMIP3setofmodels[36].Detailsofthemodellingcanbe
foundinCorneyetal.[37,38],andthemodelledprojectionsareavailablethroughtheTasma-
nianPartnershipforAdvancedComputing(TPAC)portal(https://dl.tpac.org.au/tpacportal/).
WepresentresultsbasedontheA2emissionsscenariobecauseglobalemissionsarecurrent-
lytrackingatthehigherlevelofthisscenario[39].TheA2scenarioisbroadlysimilartothe
RepresentativeConcentrationPathway(RCP)8.5,whichreplacedtheSpecialReportonEmis-
sionsScenarios(SRES)emissionsscenariosintheIntergovernmentalPanelonClimate
Change’s(IPCC’s)fifthassessmentreport(AR5)andPhase5oftheCoupledModelInter-com-
parisonProject(CMIP5).RegionalcomparisonsofprojectionsfromtheCMIP5andCMIP3
modelshavefoundsurfacetemperature,windandrainfallpatternstobehighlyconsistentbe-
tweenthearchives[40–42].ThereleaseoftheCMIP5archivemodelshasthereforenotmade
theCMIP3modelsredundant.
CurrentbaselineclimatesurfaceswereobtainedfromANUCLIMversion6.1[43],basedon
the0.01°(~1km)DigitalElevationModelforAustralia.Climatechangegridsformaximum
andminimumtemperature(Tmax,Tmin),precipitationandpanevaporationwerecalculated
relativetotheANUCLIMbaseline(1976–2005;1970–1995forevaporation),fortwofuturepe-
riodsrepresenting2040–2069and2070–2099(hereafter2050and2080,themeanvaluesofthe
30yearperiods).ANUCLIMwasusedtointerpolatetheregionalclimatemodeloutputto1km
andgeneratemonthlymeandataandthethirty-fivebioclimaticvariablesforthecurrentand
futureperiods(Table1).
GrasslandCondition
ListingofthegrasslandcommunityundertheEPBCAct1999requiresanassessmentofgrass-
landconditiontoidentifytheremnantpatchesofgreatestconservationvalue.Forthisanalysis,
grasslandsthatmetatleastsixofthesevencriteriaforlistingofLNGTundertheEnvironment
ProtectionandBiodiversityConservationAct1999wereconsideredtobeingoodcondition.
Thesegrasslandshavebeenverifiedviafieldvalidationand/oraerialphotointerpretationas
meetingallofthecriteriaforlisting(i.e.sufficientpatchsize,grasstussockcover,speciestype
andwoodyplantcover)exceptforonecriterionrelatingtominimumwildflowerspeciesrich-
ness.Thiscriterionwasnotconsideredessentialtoqualifyasbeingingoodcondition,because
speciesrichnessinTasmaniangrasslandsisoftenunderestimatedunlessfieldvalidationiscar-
riedoutinthepeakfloweringtime.Table2showstheextentofeachcommunityconsideredto
beingoodcondition.
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ChangeinThreatenedCommunitiesunderClimateChange
Table1. ThesetofbioclimaticvariablesusedintheMaxentmodelsofgrasslandcommunitiesand
species.
BioID Bioclimaticparameters
bio1 AnnualMeanTemperature
bio2 MeanDiurnalRange(Mean(periodmax-min))
bio3* Isothermality(bio2/bio7)
bio4 TemperatureSeasonality(CoefficientofVariation)
bio5 MaxTemperatureofWarmestPeriod
bio6 MinTemperatureofColdestPeriod
bio7 TemperatureAnnualRange(bio5-bio6)
bio8 MeanTemperatureofWettestQuarter
bio9 MeanTemperatureofDriestQuarter
bio10 MeanTemperatureofWarmestQuarter
bio11 MeanTemperatureofColdestQuarter
bio12 AnnualPrecipitation
bio13 PrecipitationofWettestPeriod
bio14 PrecipitationofDriestPeriod
bio15 PrecipitationSeasonality(CoefficientofVariation)
bio16 PrecipitationofWettestQuarter
bio17 PrecipitationofDriestQuarter
bio18 PrecipitationofWarmestQuarter
bio19 PrecipitationofColdestQuarter
bio20 AnnualMeanRadiation
bio21 HighestPeriodRadiation
bio22 LowestPeriodRadiation
bio23 RadiationSeasonality(CoefficientofVariation)
bio24 RadiationofWettestQuarter
bio25 RadiationofDriestQuarter
bio26 RadiationofWarmestQuarter
bio27 RadiationofColdestQuarter
bio28 AnnualMeanMoistureIndex
bio29 HighestPeriodMoistureIndex
bio30 LowestPeriodMoistureIndex
bio31* MoistureIndexSeasonality(CV)
bio32 MeanMoistureIndexofHighestQuarterMI
bio33 MeanMoistureIndexofLowestQuarterMI
bio34 MeanMoistureIndexofWarmestQuarter
bio35 MeanMoistureIndexofColdestQuarter
*bio3(isothermality)canbeinterpretedastheevennessoftemperatureoverthecourseofayear,ora
quantificationofhowlargetheday-to-nighttemperatureoscillationisincomparisontothesummer-to-winter
oscillation.Avalueof100wouldrepresentasitewherethediurnaltemperaturerangeisequaltothe
annualtemperaturerange.
**bio31wasnotusedbecausetheCoefficientofVariationcouldnotbecalculatedinareaswherethe
standarddeviationwaszero(largeareasofwesternTasmania).
doi:10.1371/journal.pone.0124014.t001
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ChangeinThreatenedCommunitiesunderClimateChange
Table2. ExtentofcurrentGTLandGPLgrasslandsingoodcondition.
Areaofcurrentextent(ha) Areaofgoodcondition(ha) %ofcurrentareaingoodcondition
LowlandThemedagrasslands(GTL) 7,535 6516 87
LowlandPoagrasslands(GPL) 13,617 7920 58
Totallowlandgrasslands(GPL+GTL) 21,152 14,436 68
doi:10.1371/journal.pone.0124014.t002
Results
Theresultsarepresentedasmapsofrelativeclimatesuitabilityforthecurrentperiod(ingrey),
andthetwofutureperiods(2050inpinkand2080inred).Futureclimatesuitabilityisshown
asthesumofallareasprojectedtobesuitablebyanyclimatemodel,theboundingbox(Araújo
andNew2007,Porfirioetal.2014).Thisislikelytobeaconservativeestimateoffuturede-
clinesinsuitableclimate,asindividualmodelsprojectedsubstantiallysmallerareasinallcases.
Blackindicatestheareaswhereallclimatemodelsagreethatcurrentlysuitableclimatewillper-
sistby2080(“persistingclimate”).
Suitabilityoffutureclimateforthegrasslandcommunities
LowlandThemedaGrasslandcommunity(GTL). Allmodelsindicateastrongcontrac-
tionofclimaticallysuitableareaforlowlandThemedagrasslandinTasmaniabymid-century
(2050)(Fig1a).HalfoftheclimatemodelsshownosuitableclimateremainingforGTLby
2080andtheremainingthreesuggestverystrongcontractions.Theseareasonlyoverlap0.1–
0.3%ofthecurrentdistribution(showninblackinFig1).
Fig1.Currentandfutureclimatesuitabilityfora)LowlandThemedaGrassland(GTL)andb)LowlandPoaGrassland(GPL)communities.White
representsareasthatarenotclimaticallysuitable.Areascurrentlyclimaticallysuitableareshowningrey,thoseprojectedtobeclimaticallysuitablebyat
leastoneofthesixclimatemodelsby2050areshowninpinkandby2080inred.Theoverlapofthecurrent(grey)andtheprojectionsto2050or2080canbe
seenindarkred.Blackindicatestheareaswhereallclimatemodelsagreethatcurrentlysuitableclimatewillpersistby2080.
doi:10.1371/journal.pone.0124014.g001
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ChangeinThreatenedCommunitiesunderClimateChange
Table3. Areaofcurrentgood-conditionLowlandgrasslandsthatareprojectedtoremainclimaticallysuitablebyeachclimatemodelby2050and
2080.
Area(ha) %ofcurrent %ofallgoodconditiongrassland
goodcondition
GTL GPL GTL GPL (LNGT)
Areaprojectedtobeunsuitablebyallmodels(2050) 6020 3886 92 49 69
Areaprojectedtobesuitable(2050):
MIROC3.2(medres) 182 508 3 6 5
ECHAM5/MPI-OM 32 1757 1 22 12
GFLD-CM2.0 83 2920 1 37 21
GFDL-CM2.1 234 1408 4 18 11
UKMO-HadCM3 123 434 2 6 4
CSIROMk3.5 89 2149 1 27 16
Multi-modalmean 124 1528 2 19 12
Areaprojectedtobeunsuitablebyallmodels(2080) 6465 3452 99 46 69
Areaprojectedtobesuitable(2080):
MIROC3.2(medres) 0 175 0 2 1
ECHAM5/MPI-OM 8 818 0.1 10 6
GFLD-CM2.0 0 424 0 5 3
GFDL-CM2.1 25 1351 0.4 17 10
UKMO-HadCM3 0 763 0 10 5
CSIROMk3.5 23 4232 0.4 53 30
Multi-modalmean 10 1294 0.2 16 9
doi:10.1371/journal.pone.0124014.t003
6516ha(87%)ofGTLarecurrentlyconsideredtobeingoodcondition(Table2).Allcli-
matemodelsagreethat99%ofthegoodconditionGTLgrasslandswillhaveunsuitableclimate
by2080(Table3).ThreemodelssuggestthatnogoodconditionGTLwillremainwithinsuit-
ableclimate,twomodelsshowbetween23and25hawillremainsuitable,andonemodelproj-
ectsonly8hawillremain(multi-modelmean10ha).However,thesesmallareasthatare
projectedtobecomeclimaticallysuitableinthefutureoccuroutsidethecurrentgeographic
rangeoflowlandnativegrassland.
LowlandPoaGrasslandcommunity(GPL). TheareaclimaticallysuitableforGPLby
2050and2080isalsoprojectedtocontractstrongly,althoughaslightlylargerarearemains
suitablecomparedtoGTL.Therearesmallareaswithinthecurrentdistributionthatarepro-
jectedtoremainsuitableforGPLbytheendofthecenturybyatleastonemodel(Fig1b).
7920haofGPLarecurrentlyconsideredtobeingoodcondition(Table2).Allmodelsagree
that46%ofthecurrentgoodconditionGPLgrasslandswillnolongerbeclimaticallysuitable
by2080(Table3).TheextentofGPLprojectedtohavesuitableclimateby2080variesbetween
models(range2–53%,multi-modelmean16%).
NaturalGrasslandandcloselyrelatedvegetationcommunities(GTL+GPL+NBA).
WhenweconsideredlowlandgrasslandsinabroadersensebyincludingtheBursaria-Acacia
woodlandandscrubcommunity,wefoundthatsuitableclimatecontractsinthefuture,but
someareasremainclimaticallysuitablewithinthecurrentdistribution(Fig2a).
Naturalwithderivedgrasslandandcloselyrelatedvegetationcommunities(GTL+GPL
+NBA+GCL). Whengrasslandsareconsideredpartofasinglebroadvegetationtypethatin-
cludesbothnaturalandderivedgrasslands,largerareasareprojectedtoremainsuitableinto
thefuture(Fig2b).However,aswiththeothergrasslandcommunities,therateofchange
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ChangeinThreatenedCommunitiesunderClimateChange
Fig2.Currentandfutureclimatesuitabilityfora)Naturalgrasslandsandcloselyrelatedvegetationcommunities(GTL+GPL+NBA),andb)Natural
andderivedgrasslandsandcloselyrelatedvegetationcommunities(GTL+GPL+NBA+GCL).Whiterepresentsareasthatarenotclimaticallysuitable.
Areascurrentlyclimaticallysuitableareshowningrey,thoseprojectedtobeclimaticallysuitablebyatleastoneofthesixclimatemodelsby2050areshown
inpinkandby2080inred.Theoverlapofthecurrent(grey)andtheprojectionsto2050or2080canbeseenindarkred.Blackindicatestheareaswhereall
climatemodelsagreethatcurrentlysuitableclimatewillpersistby2080.
doi:10.1371/journal.pone.0124014.g002
indicatedbythedifferencebetweenthegrey,pinkandredareasinFig2israpid,andtheover-
lapbetweencurrentandfuturesuitableareasisverysmall.
Dominantspecies. TheareathatisclimaticallysuitableforthegrassspeciesPoalabillar-
diereiandThemedatriandra(Fig3)contractsovertime,butsubstantialareasremainsuitable
for5ofthe6climatemodels.Oneclimatemodel,MIROC3.2(medres),projectsaverysmall
arearemainingsuitableforbothspecies.Thisclimatemodeliswetterandslightlycoolerthan
themeanofallclimatemodelsintheCMIP3archive.TheprojectionsforPoashowstronger
contractionthanThemedaoverthesametimeperiod,althoughitscurrentextentissubstantial-
lygreater.
Discussion
ClimaticsuitabilityforlowlandgrasslandsinTasmaniaisprojectedtostronglycontractbythe
endofthecentury,andtherateofthischangeisrapid.Similarchangesareexpectedtooccurin
ecosystemsaroundtheworld[44].Whilegrasslandcommunitiesmaypersistunderfuturecli-
mateconditions,theyarelikelytobeinadegraded,simplifiedortransformedstate.Conserva-
tionobjectivesmayneedtoberevisedtoaccommodatesuchchangeinmanagementand
policydevelopment.
Attemptingtomaintainthestatusquobyconservingthecurrentstructureandcomposition
ofthegrasslandcommunitiesmaynotbeaviablemanagementoptioninthelongterm.Cli-
maticsuitabilityforthecommunitiescomprisingtheLowlandNativeGrasslandsofTasmania
(LNGT),theLowlandThemedagrassland(GTL)andLowlandPoagrasslandcommunities
(GPL),isprojectedtocontractstronglybytheendofthecenturyundertheA2SRESemissions
scenarioconsideredhere.OfhighestconcernisGTL,withalmostnocurrentgrassland
PLOSONE|DOI:10.1371/journal.pone.0124014 April16,2015 9/18
ChangeinThreatenedCommunitiesunderClimateChange
Fig3.Currentandfutureclimatesuitabilityforthedominantspecies,a)Themedatriandraandb)Poalabillardiereivarlabillardierei.White
representsareasthatarenotclimaticallysuitable.Areascurrentlyclimaticallysuitableareshowningrey,thoseprojectedtobeclimaticallysuitablebyat
leastoneofthesixclimatemodelsby2050areshowninpinkandby2080inred.Theoverlapofthecurrent(grey)andtheprojectionsto2050or2080canbe
seenindarkred.Blackindicatestheareaswhereallclimatemodelsagreethatcurrentlysuitableclimatewillpersistby2080.
doi:10.1371/journal.pone.0124014.g003
projectedtobewithinclimaticallysuitableareasby2080.TheprojectedfutureofGPLisslight-
lybetterthanforGTL,butwithonlyverysmallareasofgood-conditiongrasslandsexpectedto
remainwithinclimaticallysuitableareasbytheendofthecentury.Areasthatarenotgrassland
presentlymaybecomeclimaticallysuitableinthefuture,butthecapacityforthegrassland
communityasawholetoestablishbeyondtheircurrentextentisexpectedtobeextremelylow,
becausenativevegetationishighlyfragmentedwithintheagriculturallandscapeandthefine-
texturedsoilssuitableforherbaceousgrasslandcommunitiesarenotwidespreadintheareas
projectedtobesuitable[45].Changeislikelytobetoorapidformanyspeciestorecolonise
newareas,especiallywhendistantfromthesourcelocation.Geographicshiftstonewareaswill
alsobelimitedbythecompetitiveabilityofspeciesatanyfuturesite,theinfluenceofextreme
eventsandbyotherthreateningprocessesthataffectgrasslandpersistence.
Astheclimatebecomeslesssuitableforthelowlandgrasslandcommunities,itislikelythat
therewillbeagradualchangeinspeciescompositionanddominanceassomespeciesarere-
placedbyothers.Speciesresponseswilldiffer,andoccuratdifferenttimesandrates.Somespe-
ciesmayadapttochangingconditions,orcopebyalteringtheirphenology,physiologyor
behaviour[46–48].Nearly40%oftheTasmaniangrasslandfloraisherbaceousperennials,an-
nualsandephemeralspeciesthatdowellinopenanddryenvironmentsandmayhavetraits
thatconveyadaptivecapacityinthenewconditions.Manyofthesecomponentspecieshave
broadtemperatureandrainfallranges(Seehttp://www.florabank.org.au/).Ontheotherhand,
morethan10%ofthevasculargrasslandfloraisendemictoTasmania,withhighlyspecific
habitatrequirements.Thesespecies,andotherswithnarrowthermalrequirements,willbeless
abletotoleratetemperaturechangesandmaybecomelocallyextinct.Whilelagscouldbeex-
pectedbetweenchangesinmeanclimateandthecommunityresponse,somechangesmayalso
occurearlierinresponsetotheincreasedoccurrenceandseverityofextremeeventssuchas
PLOSONE|DOI:10.1371/journal.pone.0124014 April16,2015 10/18