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Ecological
Indicators
j o ur na l h o me p a g e :w w w . e l s e v i e r . c o m / l o c a t e / e c o l i n d
A
quantitative
framework
for
assessing
spatial
flows
of
ecosystem
services
H.M.
Serna-Chavez
a,∗,
C.J.E.
Schulp
b,
P.M.
van
Bodegom
c,
W.
Bouten
a,
P.H.
Verburg
b,
M.D.
Davidson
aaInstituteforBiodiversityandEcosystemDynamics,UniversityofAmsterdam,P.O.Box94248,1090GEAmsterdam,TheNetherlands bInstituteforEnvironmentalStudies,VUUniversityAmsterdam,DeBoelelaan1085,1081HVAmsterdam,TheNetherlands cDepartmentofEcologicalScience,VUUniversityAmsterdam,DeBoelelaan1085,1081HVAmsterdam,TheNetherlands
a
r
t
i
c
l
e
i
n
f
o
Articlehistory:Received26June2013
Receivedinrevisedform25October2013 Accepted25November2013
Keywords:
Ecosystemservices Serviceprovidingareas Servicebenefitingareas Spatialecosystemserviceflows Quantitativeframework
Benefitsthroughspatialserviceflows
a
b
s
t
r
a
c
t
Spatialdisconnectionsbetweenlocationswhereecosystemservicesareproducedandwheretheyare usedarecommon.Todatemostecosystemserviceassessmentshavereliedonstaticindicatorsof pro-visionandoftendonotincorporaterelationswiththecorrespondingbeneficiariesorbenefitingareas. Moststudiesimplicitlyassumespatialandtemporalconnectionsbetweenecosystemserviceprovision andbeneficiaries,whiletheactualconnections,i.e.,ecosystemserviceflows,arepoorlyunderstood.In thispaper,wepresentagenericframeworktoanalyzethespatialconnectionsbetweentheecosystem serviceprovisioningandbenefitingareas.Weintroduceanindicatorthatshowstheproportionof ben-efitingareassupportedbyspatialecosystemserviceflowsfromprovisioningareas.Weillustratethe applicationoftheframeworkandindicatorbyusingglobalmapsofprovisioningandbenefittingareas forpollinationservices.Wealsoillustrateourframeworkandindicatorusingwaterprovisionandclimate regulationservices,astheyportrayimportantdifferencesinspatiotemporalscaleandprocessofservice flow.Wealsodescribethepossibleapplicationoftheframeworkforotherservicesandotherscalesof assessment.Wehighlighthow,dependingontheecosystemservicebeingstudied,thespatialservice flowsbetweenprovisioningandbenefitingareascanlimitservicedelivery,therebyreducingthelocal valueofecosystemservicesupply.
© 2014 The Authors. Published by Elsevier Ltd.
1. Introduction
Ecosystemservicescomprise‘theecosystemsconditionsor pro-cessesutilized,activelyorpassively,toproducehumanwell-being’
(MA, 2005;Fisher etal., 2009).The strictcouplingin the
defi-nitionofecosystemservicestohumanutilizationhasimportant consequences. First, there is a considerable differencebetween ‘potential’and‘actual’ serviceprovision,sinceecosystem condi-tionsandprocessesonlybecomeservicesoncetheyareactually usedor consumedby humanbeneficiaries(Fisher etal., 2009). Second,theremaybespatialdissimilaritiesbetweenareaswhere
∗Correspondingauthorat:P.O.Box94248,1090GEAmsterdam,TheNetherlands.
Tel.:+310205257379.
E-mailaddresses:[email protected](H.M.Serna-Chavez),
[email protected](C.J.E.Schulp),[email protected]
(P.M.vanBodegom),[email protected](W.Bouten),[email protected]
(P.H.Verburg),[email protected](M.D.Davidson).
servicesareproducedandwheretheyaretobeused.Thisimplies thatmostecosystemservicesare‘delivered’fromprovisioningto benefitingareasthrougheitherbiophysicaloranthropogenic pro-cesses.Howtheproductionconnectswithhumanbeneficiariesis acrucialfeatureoftheecosystemserviceconcept:theflowof ser-vicesinspaceandtime.Todate,theuseoftheterm‘ecosystem serviceflow’hasbeenambiguous,referringeithertogeneralservice provisionortothepathofdeliveryfromprovidingtobenefiting areas(e.g.,Chanetal.,2006;Fisheretal.,2011;Bagstadetal.,2013). Wedefineecosystemserviceflowsasthespatialandtemporal con-nectionsbetweenprovisioningandbenefitingareas.Thisdefinition centersecosystemserviceflowsasmeansforactualservice
provi-sion(e.g.,Reyersetal.,2010;Fisheretal.,2011;Turneretal.,2012)
and,hence,complementstheviewofserviceprovisionto bene-ficiaries.Informationonwhenandwherebenefitsareenjoyedis requiredfordesigningandapplyingeconomicinstruments,such aspayments forecosystemservices(Wunder,2007;Guariguata
andBalvanera,2009).Forinstance,thecharacterizationof
ecosys-temserviceflowsiscrucialtoidentifykeyplayersintheefforts tomitigateclimatechangeimpactsthroughReducingEmissions
fromDeforestationandForestDegradationmechanisms(REDD+,
1470-160X© 2014 The Authors. Published by Elsevier Ltd. http://dx.doi.org/10.1016/j.ecolind.2013.11.024
Open access under CC BY license.
Agrawaletal.,2011).Additionally,thestudyofecosystemservice flowscouldhighlightconstraintsaswellasoptionstorestorethe deliveryofservicestobeneficiaries,whichisakeytargetofAction2 oftheEuropeanUnion’s2020BiodiversityStrategy,1anda
strate-gicgoalintheConventiononBiologicalDiversity’s2020targets (‘enhancingbenefitsfromecosystemservices’,Perringsetal.,2010). Todate,studiesonecosystemserviceflowsaresparseandrather conceptual(SilvestriandKershaw,2010;Bastianetal.,2012;Syrbe
andWalz,2012).Thetemporalfeaturesofecosystemserviceflows
haverarelybeenaddressed(e.g.,Braumanetal.,2007;Bastianetal., 2012)andourunderstandingofthespatialfeaturesofserviceflows reliesheavilyonbroadcategoriesofthespatialrelationsbetween provisioningand benefitingareas(Costanza,2008; Fisheretal., 2009).Forinstance,soilformationanderosionregulationare clas-sifiedasinsituservices,becauseproviding andbenefitingareas overlapcompletely.Forstormandfloodprotection,service deliv-erydependsonproximity(Braumanetal.,2007;Costanza,2008;
Fisheretal.,2009).Forclimateregulation,thedeliveryisglobal
andomnidirectional(Costanza,2008).Recently, SyrbeandWalz
(2012)defined “the intervening spacebetween non-contiguous
providingandbenefitingareasthatinfluenceprocessvariables”as serviceconnectingareas.Thisdefinitiononlyindirectlyaddresses thespatialfeatures ofserviceflows andwithoutquantification.
This leaves a challenge quantifying the connections between
ecosystems as service providers and the beneficiariesof those services.
Spatialassessments pairingprovisioningareas withthe cor-respondingbenefitingareascanprovideinsightsintotheroleof spatialflowsinthedeliveryofaparticularecosystemservice.
Cur-rentmappingofecosystem serviceshasmoreoftenfocused on
thepotential rather thanthe actualprovision (e.g., Chanet al.,
2006;Kienastetal.,2009;Haines-Youngetal.,2012).Owingto
themisrepresentation ofactualprovision and benefits,andthe useofdifferentinputdataandmethodologies,considerable dif-ferencesintheextentofecosystemserviceprovisionandbenefits arefoundamongstudies(Eigenbrod etal.,2010;Hollandetal., 2011).Theinclusion ofthedemandside, i.e.,thecorresponding benefitandbeneficiaries,isyettobecomeanintegralpartof assess-ments(e.g.,Burkhard etal., 2012; Schulpet al.,2014).Only in afew regional-scalestudieshave thespatialfeaturesof ecosys-temserviceflowsbeenillustratedandestimated,e.g.,indirectly, bymapping‘supply anddemand’(Fisheretal.,2011; Burkhard etal.,2012),anddirectlyby,e.g.,estimatingtheperceivedbenefits fromdifferentforestedareastoagivensettlement(Palomoetal., 2012).Atlargescalesthespatialconnectionsbetweenproviding andbenefitingareasforecosystemservicesrelatedtothetradein specificcommodities,suchaswood,fishandagriculturalgoods, havewellbeenstudied(HoekstraandHung,2005;Deutschetal.,
2007;Kastneretal.,2011).Themethodologiesusedtomapand
quantifytheflowofsuchcommodities,however,areonly applica-bleforservicesthataremarketableandtrackedbyinternational tradeagencies.
Aprominentstudythatexplicitlyusedthespatialconnections betweenprovidingandbenefitingareastoevaluatespatialservice flowsistheoneconductedbyTurneretal.(2012).Theyexamined howglobalecosystemservicevaluesarerealizedandconstructed spatialmodelsofflowtoestimatethepopulationabletocapture benefits.Theirstudymakesanimportantstepbyexplicitly model-ingspatialflowstoestimatethevalueofthedeliveredbenefits.This approach,however,isdifficulttoextendandgeneralizetoother applicationsgiventheiragglomerationofindividualspatialflows intocoarsecategories.
1http://ec.europa.eu/environment/nature/biodiversity/comm2006/2020.htm.
Fig.1.Frameworktoanalyzeandquantifyecosystemserviceflows.Redcircleswith
B,representbenefitingareas,whilebluecirclewithPrepresentsprovisioningareas.
Fistheflowareawithinwhichservicesfromprovisioningareacanpotentiallybe delivered;bf isthebenefitingareanotoverlappingwithPbutwithinF;bnisthe benefitingareanot-overlappingwiththeprovisioningareaandoutsideF;bpisthe benefitingareaoverlappingwiththeprovisioningarea.
Inthisarticle,weaimtoassessthespatialflowsofindividual ecosystemservicesbymappingprovisioningareasandthe corre-spondingbenefitingareasusingagenericframework.Following thisframework,wederiveanindicatorthatcharacterizestheextent towhichbenefitingareasdependonspatialflowsfromother loca-tions.Weillustratethisapproachbymapping,attheglobalscale,a numberofillustrativeecosystemservicesthatshowdistinctly dif-ferentrelationsbetweenprovisioningandbenefittingareas.Finally, wediscusshowtheframeworkcanbeappliedinothersettingsto studytheactualprovisionofecosystemservices.
2. Materialsandmethods
2.1. Agenericframeworktocharacterizeandquantifyspatial flowsofecosystemservices
The framework we use to analyze the spatial relationships
betweenecosystemserviceprovidingandbenefitingareasis illus-tratedinFig.1.Thebluecircle(P)representsaprovisioningarea, heredefinedasthespatialunitfromwhichecosystemservicesare sourced.Thegraycircle(F)representstheflow area,delineated byamaximumorthresholddistancefromtheouterperimeterof theprovisioningarea(P)withinwhichservicescanbe‘delivered’ tobeneficiaries.Redcircles(B)representbenefitingareas,defined asthosespatialunitsinwhichecosystemservicesareneededor readilyusedorconsumed.Thebenefitingareasarefurther charac-terizedas:bp,thebenefitingareaoverlappingwiththeprovisioning area;bf,benefitingareasnotoverlappingwiththeprovisioningarea butwithintheflowarea(F);andbn,thebenefitingareanot over-lappingwiththeprovisioningareaandoutsidetheflowarea(F). Anindicatorfortheimportanceofspatialflowsforbenefitsfrom ecosystemservices(Ben.flow)canbecalculatedastheratiobetween theproportionofbenefitingareaslocatedwithintheflowarea(bf) andthetotalbenefitingareas:
%Ben.flow=
bf bf+bp ×100Table1
Spatiallyexplicitdatausedtodelineateecosystemserviceprovisioningandbenefitingareas.
Service Providingareas Benefitingareas
Data(units) Resolution Year Source Data(units) Resolution Year Source Pollination MODIS–continuous
vegetationcover(% herbaceousandtree cover) 0.092◦×0.092◦ 2000–2001 Hansenetal. (2003) Global distributionof agricultural crops dependingor benefitingfrom pollination 0.092◦×0.092◦ 2000 Lautenbach etal.(2012)
Globallandsystems map
0.092◦×0.092◦ 2000 Asselenand Verburg(2012) Waterprovision Long-termaverage
groundwaterrecharge rate(millionm3year−1)
0.5◦×0.5◦ 1958–2000 Gleesonetal. (2012) Annual groundwater abstractions (mil-lionm3year−1) 0.5◦×0.5◦ 2000 Gleesonetal. (2012)
Climateregulation Above-and below-groundcarbon density (Mgcarbonha−1) 0.5◦×0.5◦ 2000 Rueschand Gibbs(2008) Vulnerabilityof agricultural productionto climatechange (%changein total production) 0.5◦×0.5◦ 2000–2020 Wuetal. (2011)
Top-soilcarboncontent (Mgcarbonha−1) 0.5◦×0.5◦ 2000 Hiedererand Köchy(2012) Netecosystem productivity (Mgcarbonha−1year−1) 0.5◦×0.5◦ 2000 Sitchetal. (2003)
HighvaluesforBen.flowindicate:(1)ahighimportanceofthe spatialflowsforthedeliveryoftheservicetothebenefitingareas, and(2)alargerspatialsegregationbetweenprovisioningand ben-efitingareas.
We present the application of the framework and indicator
basedonlocal-scale flowsusingbiotic pollinationservices.The availableknowledgeonhabitatrequirementsandforagingranges ofpollinators(Kremen etal.,2007),aswellasthegeographical locationofcropsbenefitingfromthis service(Kleinetal.,2007;
Lautenbachetal.,2012),allowsacomprehensivedepictionoftheir
spatialflows.Themajorityofecosystemservices,however,show importantdifferencesintheirspatialcharacteristicsofprovision andflow.Thatiswhy,wealsopresenttheapplicationofour frame-workusingtwootherexamplesofecosystemserviceswherethe connectionsbetweenprovisioningandbenefittingareasare under-pinnedbydifferentprocessesandoperateatlargerscales.These additionalexamplesareonlymeantforillustration,forwhichwe selectedwater provisionandclimateregulationservices.Forall ecosystemservicesweuseglobalmapsofprovisionandbenefits
(Table1),delineatingtheflowareabasedoncurrentknowledge
(Table2),andmakingassumptionsmatchingglobalscaledata
avail-ability.AllanalyseswereconductedinArcGISv10.1.andRv2.15.2
(RDevelopmentCoreTeam,2011)software.
2.2. Local-scalespatialecosystemserviceflow:pollination
Providedtocroplandsbyunmanagedpollinators,pollination servicesrelyonthepresenceofsuitablehabitats(Kremenetal.,
2007;Lonsdorfetal.,2009).Theabundanceofpollinators,andlikely
theircontributiontoeffectivecroppollination,decreasesas isola-tionfromsuitablehabitatsincreases(Rickettsetal.,2008;Garibaldi etal.,2011).Tomapprovisioningareasataglobalscaleweused thepercentageofvegetationcoverinnaturalandsemi-naturalland covercategoriesaspotentialhabitatforunmanagedpollinators.We usedremotelysenseddataonherbaceousandtreecover(MODIS,
ContinuousVegetationCover; Hansenetal.,2003)within natu-ralandsemi-naturalgloballandsystemscategories(Asselenand
Verburg,2012).Theselandsystemcategoriesincludeddense
for-est,naturalgrassland, andmosaiccover offorestand grassland withextensivecroplandorwithfew livestock.Herbaceous and treecoverwithintheotherlandsystemcategorieswasassumed tobemoreintensivelymanagedand, hence,unlikely tocontain significantpollinator habitat.For thedense forestcategory, we onlyincludedforestedgesinthevicinityofagriculturalareasas partofpollinatorhabitat(Garibaldietal.,2011).Forestedgeswere selectedbyneighborhoodanalysis,removingthosecellsentirely surroundedbythesamelandsystemcategory.
Localcasestudieshavedeterminedthresholdsforhabitatcover thatenableoptimalpollinationtosurroundingcroplands(Kremen
etal.,2004;Rickettsetal.,2008).Becauseofdifferencesinspatial
scalesandtypesofdataused,suchthresholdscouldnotbereadily appliedtoourstudy.Therefore,wefirstassessedtherelationship betweentreeandherbaceouscoverandthecroplandcover occur-ringwithinadistanceof2km.The2kmthresholdwasusedsinceat greaterdistancesvisitationratesfromunmanagedpollinatorsare likelytobenegligible(Rickettsetal.,2008;Garibaldietal.,2011).
Thisassessmentshowedthat witha treeandherbaceous cover
of45%mostofthesurroundingcroplandareas(95%±5%)would occurwithinadistanceofapproximate2km(AppendixA).With theresults,werefinedtheglobalprovisioningareasofpollination servicesasthosewithtreeandherbaceouscover≥45%(hereafter ‘potentialpollinationhabitat’).
Areasbenefitingfrompollinationservicesweredefinedasthose globalareaswherecropsdependingorprofitingfrombiotic polli-nationareproduced.Thesebenefitingareasweredelineatedusing aglobalmapofthedistributionof60cropsdependingor profit-ing,tovaryingextents,frompollination(Lautenbachetal.,2012). Wethenevaluatedtheextentofthespatialoverlapbetweenthe
provision and benefit maps (bp). The spatial flow to
Table2
Keyecosystemserviceprovisioningandbenefitingareas,andthespatiotemporalcharacteristicsofflowamongthem.
Ecosystemservice Areasofecosystemservice Flow (Human)Benefits
Provision Benefits Spatiotemporalscale Processallowing Pollination Naturaland
semi-natural habitats •Grassland •Shrubs •Heathland •Forestpatches •Forestedges Agriculturalareas dependentonor profitingfrombiotic pollination
Rapidandlocal(range restricted)
-Foragingrangesof pollinatorspecies -Pollentransportationand deposition
-Abundanceand effectivenessofpollinating organisms
-Direct:increasedand/or realizedcropyield -Indirect:intermediaryin otherservices,e.g., reproductionofplants involvedinclimate regulation
Waterprovisionforirrigation Locationof groundwater basinsandtheir annualrecharge Agriculturalareas dependenton groundwaterirrigation Basin-wide.Water availabilityis precipitation-dependent (seasonality) -Infrastructurefor extraction,distributionand irrigation
-Basinrechargerate, whichdependson:
•Soilinfiltrationcapacity •Topography
-Cropyield -Monetary
Climateregulation Primarily,tropical (incl.peatforests) andborealforest (hotspots) Various Here:tropical, sub-tropicaland mid-latitude agriculturalareas vulnerabletochanges inprecipitationand temperature Globalnon-excludable, andlong-term (decades) Local-to-regional,and rapid(days,months)
-Vegetationandsoil interactionswiththe atmosphere,suchas:
•Photosynthesis •Soilandplant evapotranspiration,soil heterotrophicrespiration •Albedo
•Plantaerosolproduction •Heathexchange -Globalatmospheric mixing
-Avoidedorameliorated:
•Decreasedcropyieldsin tropical,sub-tropicaland mid-latitudes
•Decreasedwater availability
•Increaseinvector-borne exposureandwater-borne diseases
•Increasedfloodrisk •Increasedmortalityform heatstress
pollinatorhabitatareas2kmineverydirectionandre-evaluating theextentofspatialoverlapwithcroplandareas(bf).
2.3. Large-scaleecosystemserviceflows
2.3.1. Groundwaterprovision
Toillustratetheanalysisandquantification ofregional-scale ecosystemserviceflows,wemappedgroundwaterrecharge(i.e., provision)andabstraction(i.e.,benefit)forcropirrigation follow-ingourframework(Fig.1).Astheaimofthisparticularexample isnotanexhaustivequantificationofserviceprovisionandflow, we didnotaccount for othertechnical solutionsthat influence theavailabilityofwaterforirrigation,suchasrainharvestingor theuseof reclaimedwastewater.Forgroundwaterprovisioning andbenefitingareasweusedglobalmapsoflong-termrecharge andabstractionsforirrigation(inmillionm3year−1;Gleesonetal.,
2012),respectively.Asthesedataarequantitativeandofthesame
entity,we estimatedto whatextent groundwaterrechargecan
meetabstractionsforirrigation.Weassumedthatspatialflowsof availablegroundwatertoareasofabstractionsoccuronlywithin basins,becausetransportofgroundwaterisconstrainedtowithin basinsandtothepresenceofinfrastructureforextractionand dis-tribution.Onlymajorgroundwaterbasins,whicharethosewith amappedrechargerate>2mmyear−1 (BGRandUNESCO,2008), weretakenintoconsideration.
Foreachglobalgroundwaterbasin,weanalyzedtheextentto which abstractionsare covered byavailable recharge.Thiswas calculatedas thebasin-widedifferencebetweentheaverageof abstractionsandrecharge,whichrepresentsthetotalofbp+bf.By doingthis,allrechargeisallocatedtoabstractionsregardlessthe locationofwhereboth occurred.Toillustratetheapplicationof ourframeworkforregionalflowsinmoredetail,wecalculatedthe amountofabstractionsforirrigationthatcanbecoveredby spa-tialflowsofgroundwater(bfandBen.flow)inthreebasins,i.e.,the greatplains(US),Ganges(India)andnorthChinabasin.Theselected groundwaterbasinsillustratethreedifferentcaseswherebfdiffers
inmagnitudetomeetabstractionsforirrigation.Foreachbasin, weusedtheaverageofrechargeandabstractionstocalculatethe extenttowhich(1)rechargemeets‘on-the-spot’(i.e.,withinthe samegrid-cell)abstractions(bp),and(2)theremainingrecharge availabletoflowwithinthebasin(bf).Thesetwoestimateswere thenusedtocalculatetheBen.flowforeachofthethreebasins.
2.3.2. Climateregulation
The provision of climate regulation includes
biogeochemi-cal(e.g.,carbonsequestration)andbiophysicalmechanisms(e.g., evaporative cooling) (Foley et al., 2003; Chapin et al., 2008).
As quantifications of the biophysical mechanisms are scarce
(Anderson-Teixeiraetal.,2012),weonlyaccountedforthestored
andsequesteredcarboninvegetationandtopsoilasrepresentative ofaclimateregulationservice.Forthispurpose,aglobalcarbon densitymap (Mgha−1)wasconstructedbyaddingtheamounts ofcarbonstoredinlivingvegetation(above-andbelow-ground;
RueschandGibbs,2008)andintopsoil(0–30cmdepth;Hiederer
and Köchy,2012).From outputof theLPJ-DynamicGlobal
Veg-etationmodel(Sitch etal., 2003), we selectedareaswitha net ecosystemproductivity(NEP,inMgha−1year−1)greaterthanzero, i.e.,netadditionstotheterrestrialcarbonpool.Areaswithinthe top25% quartileofthecarbon densitymap wereoverlaidwith thenetsinksfromtheNEPmaptodelineatehotspotsofprovision. Thishotspotsmapwasusedasprovisioningareasofclimate reg-ulationandrepresents(1)areasofhighabove-andbelow-ground carbondensity,(2)netcarbonsinks,and(3)theareaswhereboth overlapped.
Climateregulationserviceshaveawiderangeofindirectand directbenefits,beyondoff-settinganthropogeniccarbonemissions. For illustration purposes, and because of a lack of global-scale mapsofmultiplebenefitsfromclimateregulation,weonly con-sideredagriculturalproductionasabeneficiary.Weusedamap
of agricultural production vulnerable to changes in
tempera-tureandprecipitationunderabusiness-as-usualclimatechange scenario (Wu et al., 2011). This map shows projected changes
Fig.2. Pollinationserviceflowfrompotentialhabitattocropland.(A)Spatialsimilaritiesbetweenprovisioningandbenefitingareas(24.7%,bp),whichentailsthatwithin overlappingcellsthepotentialhabitatcovercanenablepollinationserviceflowstothesurroundingcroplands.(B)Theincreaseinspatialsimilarities(31%,bp+bf)by
accountingfortheflowareaforunmanagedpollinatorstoadjacent,non-overlapping,croplandareas.About68%oftheareaswithcropsprofitingordependingonbiotic pollinationareoutsidetheflowareas(bn).
in total production of wheat, rice, soybeans and maize for the 2000–2020period(asa percentage changeintotal production; (Wuetal.,2011).Theseagriculturalareasrepresentthe produc-tionoffourofthetop-tenglobalagriculturalcommodities(FAO stats:http://faostat3.fao.org/home),whichwillbenefitindirectly
fromthebiogeochemicalmechanismsofclimateregulation.We
onlyselectedareaswhereadecreaseinagriculturalproductionis projected.Toassesstheproportionofbenefitingareasdepending onspatialflowsofclimateregulationservices,weestimatedthe overlapbetweenprovisioninghotspotsandbenefitingareas(bp). Theflowarea(F)forthedeliveryofindirectbenefitsthrough car-bonsequestrationandstoragecanbeconsideredglobal(Table2), thusallareasthatdonotoverlapwithprovisioninghotspots(bp), arewithinflowarea(bf).Itisimportanttonote,however,thatin thiscasetheserviceflowisindirectandthatimpactsofclimate regulationmaybespatiallydependent.
3. Results
3.1. Local-scalepollinationserviceflows
Oftheglobalcroplandareasthatwouldbenefitfrom pollina-tion,24.7%overlapwiththeprovisioningareas(bp).Fortheseareas, thepollinationserviceflowswould occurwithintheareaitself
(‘Potentialserviceflow’inFig.2A).Additionally,another7.7%(bf)is supportedbypollinationserviceflow(Fig.2B).Thislastdelineation ofserviceflowsassumesthattheconnectivityanddistributionof habitatwithintheprovisioninggridcells is sufficienttoenable flowstoadjacentopenlandcoverwithlittleornopollinator habi-tat.Overall,thisanalysisindicatesthat32%oftheglobalpollination servicesdeliveredtocroplandscanberealized(bp+bf).Abouta quarterofthisglobalserviceswouldberealizedthroughspatial flows(Ben.flow=24%).Thisleavesabout68%oftheglobal agricul-turalareasoutsidetheflowareaofunmanagedpollinators(bnin
Fig.1).Theregionswherepollinationflowsfrompotential habi-tatareunlikelyarethelarge-scale,homogeneous,croplandcover in,e.g.,MidwestUSA,andEastAsia(Fig.2B). Theseareaslikely relyonartificialserviceprovisionbyusing,e.g.,domesticatedbee colonies.
3.2. Largescalespatialflows 3.2.1. Groundwaterserviceflows
A global map illustrating the range of differences between groundwaterabstractionsforirrigationandrecharge(bp+bf)and for all major groundwater basins in the world is presented in
Fig.3A.GroundwaterbasinsinthearidregionsofnorthernMexico, SaudiArabiaandIrandisplaynegativewaterbalances,duetotheir
Fig.3. Large-scaleecosystemserviceflows.(A)Groundwaterprovisionforirrigation.Netbasin-widebalanceafteraverageabstractionsforirrigationweresubtractedfrom theaveragerecharge(millionm3year−1).Resultsaccountforbpandbp,asallrechargeisallocatedtoabstractionsregardlesstheirlocation.Temperateandmid-latitude
regionsshowgreaterdemandsonserviceflowstofulfilltheabstractionsforirrigation.Boxesdelineatetheselectedbasinsfordetailedanalysisofbenefitsthroughspatial serviceflows(inTable3)(B)Globalclimateregulationservice.Spatialconnectionsbetweenvulnerableagriculturalareasandhotspotsforclimateregulationservices.Overlap isconsiderable,with21%ofglobalagriculturalareasoverlappingwithhotspotsofprovision(bp),whiletheremaining79%areas(bf)relyonspatialflows.
lowrechargeratesandlargeabstractions.Groundwaterbasinsin theCongoandAmazonregionsdisplayhighpositivenet
ground-water balances due to their high natural recharge and scarce
abstractions.
DetailedexamplesofthecalculationofBen.flowindicatorare givenforthreebasins(Table3).Thesebasinsdifferintheamount ofabstractionscovered byoverlapping recharge,and byspatial flowsofrecharge.Thegroundwaterabstractionsthatarecovered with‘on-the-spot’recharge(bp)rangedfrom7%to82%,whilethe remainingrechargethatwouldbeabletocoveradditional abstrac-tions(bf)rangedfrom2%to21%.Ben.flowrangedfrom10%to75%. Inallcases,agroundwaterdeficitremained.
Table3
Ben.flowindicatoranditscomponentsforthreeillustrativegroundwaterbasins. NomenclatureafterframeworkinFig.1.
Basin bp bf %Ben.flow
USAhigh-plains 8% 2% 20%
UpperGanges 82% 9% 10%
NorthChina 7% 21% 75%
bp:theamountofabstractioncoveredby‘on-the-spot’recharge.
bp:theamountofabstractioncoveredspatialflowsofrecharge.
3.2.2. Climateregulationserviceflow
The areas delineated as hotspots of provision of climate regulation services mainly comprise tropical and boreal forest areas(Provisioninghotspotsin Fig.3B).These forestedareasare recognizedasimportantbiophysicalandbiogeochemicalhotspots ofglobalclimateregulation(HouseandBrovkin,2005).The ben-efitingagriculturalareasshowimportantclustersincentraland EasternEurope,ChinaandtheUSA.Decreasesintotalproduction upto88%areexpectedintheseregionsuponclimatechange(Wu
etal.,2011).
Thespatialdisconnectionsbetweenprovisioningandbenefiting areasareconsiderable,withonly21%ofbenefitingareas overlap-pingwithprovisioningareas(bp,Fig.3B).Asagriculturegenerally doesnotprovideclimateregulationservices,thisoverlapislikely duetotheinclusionofaprojectedincreaseintotalsownareaswhen evaluatingfuturevulnerabilityofagriculturalproduction(Wuetal., 2011).Inthisexampleallbenefitingareasarewithintheflowarea (bp+bf=100%),giventhenon-rivalandnon-excludable character-isticofprovisionandflow(Costanza,2008).Oftheglobalbenefiting areas,79%ofthebenefitswouldberealizedthroughspatialservice flows(Ben.flow).
Thespatialflowsofclimateregulationservicesarebywayof global atmospheric connections,which entailnotransport lim-itations. Giventhetime neededfor atmosphericmixing (Meehl
etal.,2007;Bastianetal.,2012),theglobalbenefitsthroughcarbon sequestrationandstoragebyecosystemsarelaggedintime.This iswhytheindirectglobalbenefitsfromclimateregulationservices aresegregatednotonlyinspacebutalsointime.
4. Discussion
4.1. Aframeworkforecosystemserviceflows
Weintroducedandillustratedaframeworktocharacterizeand analyzeecosystemserviceflowsbetweenprovisioningand bene-fittingareas.Weusedpollinationservicesandtwoothercasesto illustratekeyvariationsin theextentandlocation ofbenefiting areasaswellasinspatialflows(Table2).Fortheseexampleswe usedglobal-scaledatatodelineateecosystemserviceprovisioning andbenefitingareas,usingsimplifiedrepresentationsof ecosys-temservice‘supply’and ‘demand’thatfit availabledataat this scale.Weusedpollinationservicestopresenttheassessmentof spatialflowsfollowingourframework(Fig.2).Bycomplementing theassessment ofpollinationserviceflowswiththeillustration
of water provisionand climateregulation flows,we were able
toshow how depending on the service analyzed, provisioning
andbenefitingareascanhaveintrinsicallydifferentcharacteristics, whichimpliesthatspatialflowsarerequiredtoenjoybenefitsfrom mostecosystemservices.Thespatialinformationneededto delin-eateprovisioningand benefitingareasfollowingourframework isreadilyavailableformostecosystemservices,whichallowsthe extensionofthestudyonspatialflows.InTable4weoutlinethe applicationoftheframeworktodifferentecosystemservices.
Thegenericframeworkwepresentbuildson,andextends,the fewstudiesthathaveexplicitlyillustratedorevaluatedthespatial overlapbetweenecosystemserviceprovisionandbenefitsat land-scape(e.g.,SyrbeandWalz,2012),regional(e.g.,Fisheretal.,2011;
Palomoetal.,2012),continental(e.g.,Maesetal.,2011)orglobal
scale(e.g.,Turneretal.,2012).Theframeworkisaparsimonious approachtostudythespatialconnectionsbetweenprovisioning andbenefitingareas,andcanbereadilyusedforthemajorityof ser-vicesgivencurrentdataavailability.TheBen.flowindicatorprovides asimplemeasuretoidentifytheproportionofareawhere bene-fitsaredependentonspatialflows.ThecalculationoftheBen.flow indicatordependsonthedelineationofaflowarea(FinFig.1).This delineationofflowareaallowstheidentificationofthoseareasthat dependonspatialserviceflowstoenjoybenefitsandisafirststep towardthecharacterizationandquantificationofspatialflowsand actualecosystemserviceprovision.Theanalysesherepresented highlighthow theflow area(F)is characteristicofeach ecosys-temservice,and canbeunderpinnedby theforaging rangesof mobileorganisms(asinpollination),basinareaandinfrastructure (asinwaterforirrigation),orbiophysicalprocesses(asinclimate regulation).
Intheanalysisoflocal-scaleflows,unmanagedpollinatorsliving insuitablenaturalandsemi-naturalhabitatsprovidepollination servicestonearbycroplands.Giventhespatialsegregationbetween habitatandcropland(Kremenetal.,2007),benefitingareasare,by definition,completelydependentonpollinationserviceflowsfrom adjacenthabitats.Thestudyofserviceflows,therefore,requires accountingforathresholddistancefromprovidingareasto iden-tifythecropareasthatcanbenefitfrompollinationservices(sensu FinFig.1).Forpollination,suchinformationisavailablefromfield studies(Rickettsetal.,2008;Garibaldietal.,2011).Here,weused suchthresholddistancetoestimatethepercentageofbenefiting areasthatarecoveredbyspatialflows.Thedistinctionbetween serviceflowsthatwouldoccurinareaswherebothprovisionand benefitingareascanbefound(bp),andflowsbetweenadjacent pro-visionandbenefitingareas(bf)butwithintheflowarea(F)showed
howmorethanhalftheglobalcroplandareasthatwouldbenefit frompollinationareoutsidetheflowareafrompotentialhabitats (Fig.2).Thesefeaturesofspatialflowalsohighlightthe possibil-itiesfor improvingdeliverytobenefiting areas:by restoringor re-distributinghabitatcoveranditsconnectivity,orrelocatingthe benefitingcroplandareas.
Toillustratethecharacterizationofspatialflowsthatoperate atlargerscalesfollowingthesameframework,weusedexamples ofwaterprovisionandclimateregulationbecausetheyrepresent differentprocessesunderpinningprovisionandflow.Inthesetwo cases,ecosystem serviceflow is establishedthrough hydrologi-calprocesseswithingroundwaterbasinsand,indirectly,through theclimatesystem,respectively.Theirrigationinfrastructurewill affectthedistanceanddirection(sensuF)thatavailablerecharge follows tomeet abstractions. For our illustrative examples,we assumedthattheinstalledinfrastructureisabletodeliverservices throughoutthebasintoestimatebp+bfforeachglobal groundwa-terbasin(Fig.3A)andBen.flowindicatorinthreecases(Table3). For theindirectbenefitsfromclimateregulationservices,there areknownspatialandtemporalsegregationsbetween provision-ing and benefiting areas (Fig. 3B). In this case, the perceived
benefits through carbon sequestration and storage cannot be
attributedtoaparticularprovisioningarea(P),becauseoftheflows throughtheglobalclimatesystem,whichmakes the differenti-ation ofbenefiting areasintobp or bfnot crucial. Ontheother hand,for thedirect benefitsof climateregulation through bio-physical mechanisms,suchas evaporative cooling (Foley et al., 2003),theneighboringprovisioningareas(P)arelikelythemain contributors. The direct, smaller-scale, flowsof climate regula-tionserviceswerenotincludedinouranalysis,becauseageneral maximumor thresholddistanceof a flow area(F)is noteasily derived.
Inthisstudyweintegratedallbenefitingareastoanalyzespatial serviceflows.Aspresented,theframeworkcanalsobeappliedto studythebenefitingareasindividually,whichwillthenhighlight thosethatrelymoreonspatialflowstobenefitfromecosystem services.Thischaracterizationwouldconsiderthebenefitingareas equally, regardless any difference in size or distancefrom the outerperimeterofprovisioningorflowareas.Thedifferentiation betweenbenefitingareaswouldbeattributedtothedifferencesin overlapwithprovisioningareas(bp),withtheflowarea(bf)and, hence,intheBen.flowindicator.
Theframeworkmayalsobeextendedtotheprovisionof multi-pleservices,withknowntrade-offsandsynergies.Suchapplication wouldrelyonthepossibilitytodelineatea‘common’flow area andtheidentificationofbeneficiaries.Inspiteofthedifferences betweenecosystemservices,somedosharekeycharacteristicsin theirprovisionandspatialflow.Forinstance,thecharacteristicsof provisioning,benefitingandflowareasforpollinationservicesare similartothoseforbiologicalcontrol(ThiesandTscharntke,1999;
Ruschetal.,2013),whichfacilitatestheanalyzesofbothservices
withourframework.
4.2. Caveatsandfutureresearchneeds
A proper characterization and quantification of ecosystem
serviceflowsrequirestheidentificationofthespatiotemporal fea-turesin provisionandflow,aswellasthequantificationofthe processesinvolved.Ourframeworkandindicatorcanserveasfirst approximationtoevaluatetheimportanceofspatialserviceflow (asinFig.2)andtoquantifythedeliveredbenefits(asinTable3). Theillustrationsinthispaperbasedonglobaldatadid,however, notexplicitlyaddresstheindividualflowpathsbetween provision-ingandbenefittingareas.The‘ServicePathAttributionNetwork’ (SPAN)frameworkfromthe‘ArtificialIntelligenceforEcosystem Services’project(ARES;Villaetal.,2009;Bagstadetal.,2013),helps
Table4
Illustrationofframeworktoevaluatespatialserviceflowstobeneficiaries.NomenclatureofspatialserviceflowframeworkafterFig.1.
Ecosystemservices F bf bp bn pa
Pollinationandbiologicalcontrol
P
bpbfB
F
bn
Relativetothe homeandforaging rangeofthemobile organism(s) providingthe service Adjacent (non-overlapping) croplandareas, dependentonor benefitingfrom theseservices
Areaswithboth suitablehabitatfor providingagents andbenefiting cropland Dependentor benefiting croplandareas outsidethe flowarea Areasof suitable, naturaland semi-natural, habitat
Waterprovisionforirrigation
B
P
P
B
bpP
F bf b fBasinarea Areaswithwater abstractionsandno orlittlewater availability—rel.to naturalrecharge rates
Areaswithboth water availability—rel.to recharge—and abstractions None,withina particularbasin Areasthat experience natural groundwater recharge
Moderationofextremeeventsanderosionprevention
P
bpB
bf bfB
F
Areasbetweenthe extremeeventand thebenefiting areas,e.g.,for erosionprevention, uplandvegetated areasasthereisa slope-dependent relationship Areasof settlementsor infrastructure vulnerableto extremeevents
Areaswithboth provisionand benefiting settlementsor infrastructure Dependson degradation processes considered Area,naturalor semi-natural, thatbuffers extremeevents orpreventssoil erosion,e.g. wetlands, floodplainsand reservoirscan bufferfloods Provisionoffoodandrawmaterials
B
B
B
B
P
P
B
bp bf F bf bf bf Delineatedby anthropogenic processesof storage, commercialtrade, aswellasdemandAreaswherethe exported productionis delivered Domestic consumptionor use Demandingor necessityareas thatcannot import Total production Climateregulation
P
B
bpB
bf bf FGlobal Areasthatdonot overlapwith provisioning—high carbondensityor carbonsink—areas
Areasthatboth provideandbenefit fromclimate regulation
None Areaswithhigh carbondensity andnetcarbon sequestration rates
connectingbiophysicalmeasuresofserviceprovisionwithhuman useandconsumption,byconnectingbothspatiallocations.SPAN alsoincludesmodelsofspatialflowandallowsanapproximationon theuncertaintyofserviceprovisionandvalueofbenefits(Silvestri
andKershaw,2010;LogsdonandChaubey,2013).Thisapproach,
explainedinBagstadetal.(2013)remainsdata-and knowledge-intensive,whichstronglylimitsitsapplicabilityatlargescalesand formanyecosystemservicesandareaswhererelevantdataisnot available.
Tohelpimprovingtheanalysisofspatialflowswesuggest build-ingfutureextensionsfollowing landscapemetrics.Forinstance,
landscape proximity and connectivity metrics can help assess
whichbenefiting areasrelyonwhich provisioningareasfor the delivery of services, given a defined distance from provision-ingareas(F).Thelattercanalsohelpassessingthepermeability andresistancetoservicedelivery,assuchcomplementary
land-scape metrics can consider the constraints posed by defined
anthropogenic or natural barriers within a given spatial flow
area.
Coupledtothespatialserviceflowsthatcanbeassessedwith ourframework,therearekeytemporalfeaturesofserviceprovision andflow.Todate,explicitrecognitionoftemporalfeaturesof provi-sionandflowisonlyslowlyemerging(Braumanetal.,2007;Bastian etal.,2012),andsuchfeaturesareyettobeintegratedinecosystem
serviceassessments(Brownet al.,2005;Kochet al.,2009).The integrationof temporalfeatures intoassessmentsis notreadily supportedbyavailableframeworksgivenalsothevastdifferences intemporalfeaturesamongecosystemservices(Rodriguezetal., 2006).Someunderstandingonthetemporal features, however, maybeobtainedfromtheprocessesdeterminingtheserviceflows, asanalyzedinourframework.Forinstance,local-to-regional
ben-efits of climate regulation, as influenced by water and energy
exchangesbetweenvegetationandatmosphere,areexperienced
rapidly,withindaystomonthsbasis(Pielkeetal.,1998).Onthe otherhand,theglobalindirectbenefitsthroughthemodulation ofatmosphericconcentrationsofgreenhousegasesaresegregated fromprovisionintime,giventhetimerequiredforatmospheric mixing(Pielkeetal.,1998;Meehletal.,2007).Toillustratethis,we highlighttheimportanceofthedelineatedprovisioninghotspots (Fig.3B),basedonaverageNEP,aspast,presentandfutureservice providers.Thehotspotsarepastserviceproviders,fortheprocesses thatleadtohighcarbondensitiesinlivingvegetationandsoils; present,forthecontinuationofsequestrationandthestabilityof currentcarbonstocks;andfuture,sincethelong-termstabilityof theterrestrialcarbonpool,andfluxesofenergyand greenhouse-gasescanmitigate,orameliorate,someoftheexpectedimpacts ofglobalclimatechange.Acknowledgingaswellasaccountingfor thesetemporalfeaturesofclimateregulationservices,aswellas foranyotherecosystemservice,iskeytoassesstheactualbenefits fromecosystems.Table2describesthetemporalcharacteristicsof flowfortheecosystemservicesdiscussedinthepaper.
Thedeliveryofecosystemservicesandthelinksbetween pro-visioningandbenefittingareasasquantifiedinourframeworkalso hasacriticalsocio-ecologicaldimension.Therefore,itrepresents
akey componenttomake theecosystemserviceconcept
oper-ational(Kremenand Ostfeld,2005;Nicholson etal.,2009).This isillustratedin astudyonecosystemserviceflowsprovidedby
Palomoet al.(2012).Theyidentifiedand estimatedtheamount
ofecosystemservicesperceivedassuchbythelocalpopulation surroundinga nationalprotected areaand otherforestedareas. Theyexplicitly used theconcept of ecosystem service flowsto illustratetheextenttowhich benefiting areasenjoyedservices fromneighboringanddistantprovidingareas.Inthiscase
account-ing for ecosystems service flows helped to support thedesign
ofbetter management approaches,evaluation of trade-offs and informeddecision-makingbydeterminingwheretheservicesfrom aprovisioningareaarebeingdeliveredtoparticular
beneficiar-ies(GuariguataandBalvanera,2009;SilvestriandKershaw,2010;
Crossman et al., 2013).We envision that the quantification of
ecosystemserviceflows,asprovidedbyourframework,mayaid supportingdecisionmakinginsimilarsettingselsewhere.
5. Conclusions
Theanalysesinthis paperhighlight howthespatial charac-teristicsoftheflow betweenprovisioningand benefittingareas arespecifictoeachservice.Thestudyofecosystemserviceflows requiresguidelinesforassessmentsthatareappropriateforall ser-vicesaswellasallspatialscales.Thegenericframeworkforanalysis ofspatialflowsofecosystemservices,aspresentedinthispaper, canbeafirstbasis tosupportsuchassessments.Understanding thespatiotemporalcharacteristicsofproduction,flowanddelivery tobeneficiaries,andaccountingtheprocessespinpointingthem, arecrucial to make theecosystem service conceptoperational. Ourframework mayaidtheevaluationof optionstorestoreor improvethedeliveryofbenefitsnowandinthefaceofglobal envi-ronmentaland land-usechange.Thestudyofecosystemservice flowsiskeyinassessmentsaimingtodesigneconomicinstruments basedonactualserviceprovision,andforthecharacterizationand
managementofgeopoliticaldisparitiesbetweenserviceproviders andbeneficiaries.
Acknowledgements
Wethanktwoanonymousreviewersfortheirhelpfulcomments onanearlierversiononthismanuscript.WealsothankWu Wen-binforfacilitatingdata.H.M.S.C.andM.D.thanktheNetherlands OrganizationforScientificResearch(NWO)forprovidingfunding (InnovationalResearchIncentivesScheme,VIDI).P.V.wouldliketo thanktheFP7projectOPERAsforfinancialsupport.C.J.E.S. acknowl-edgesERA-NETBiodiversaprojectCONNECTforfinancialsupport. WearegratefultoNigelHarleforbrushinguptheEnglishinthis manuscript.
AppendixA. Supplementarydata
Supplementarymaterial relatedto this articlecanbe found, in the online version, at http://dx.doi.org/10.1016/j.ecolind.
2013.11.024.
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