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EcologicalEconomics37(2001)257–270ANALYSISTheeconomicvalueofwetlandservices:ameta-analysisRichardT.Woodward*,Yong-SuhkWuiDepartmentofAgriculturalEconomics,TexasA&MUniersity,2l24TAMU,CollegeStation,TX77843-2124,USAReceived30March2000;receivedinrevisedform15November2000;accepted16November2000AbstractThenumberofstudiesquantifythevalueofwetlandsandtheservicesprovidedbytheseecosystemsisrapidlyexpanding.Thetimeisripeforanassessmentofwhathasbeenlearnedfromthisliterature.Usingresultsfrom39studies,weevaluatetherelativevalueofdifferentwetlandservices,thesourcesofbiasinwetlandvaluationandthereturnstoscaleexhibitedinwetlandvalues.Whilesomegeneraltrendsarebeginningtoemerge,thepredictionofawetland’svaluebasedonpreviousstudiesremainshighlyuncertainandtheneedforsite-specificvaluationeffortsremainslarge.©2001ElsevierScienceB.V.Allrightsreserved.’ecologicalservicesisarelativelyrecentphenomenon.Historically,wet-landswereviewedasawasteofvaluablelandthatcouldonlybe‘improved’throughdrainageanddestructionofthewetland(MitschandGosselink,1986).Today,whilethereisnowwidespreadrecognitionthatwetlandsprovidevaluableeco-logicalservices,thereremainsubstantialdebatesoverwhetherparticularareasareintheirhighesteconomicuseaswetlands,andtowhatextentpublicandprivateresourcesshouldbeusedfortheirprotectionandrestoration.Hence,thereisagrowingneedtoquantifythevalueofwetlandservices.Theservicesprovidedbywetlandsincludehabi-tatforspecies,protectionagainstfloods,waterpurification,amenitiesandrecreationalopportu-nities.Becausetheseservicestypicallyhavenomarketprice,ameasureoftheirvaluescanonlybeobtainedthroughnon-marketvaluationtech-niques.Manywetlandvaluationstudieshavebeenconductedandtherangeoftheestimatesisre-markable.ArecentreviewbyHeimlichetal.(1998)lists33studiesoverthelast26yearswithperacrevaluesrangingfromUS$0.06toUS$22050.Evenwithinthesamestudylookingatasingleecosystemfunction,BatieandWilson(1978)findvaluesperacrethatdifferbytwoordersofmagnitudefromonesitetoanother.Thepurposeofthispaperistoassesswhetheranysystematictrendscanbedistilledfromthe*Correspondingauthor.Tel.:+1-979-8455864;fax:+1-979-8454261.E-mailaddress:r-woodward@tamu.edu(R.T.Woodward).0921-8009/01/$-seefrontmatter©2001ElsevierScienceB.V.Allrightsreserved.PII:S0921-8009(00)00276-7R.T.Woodward,Y.-S.Wui/EcologicalEconomics37(2001)257–270258breadthofwetlandvaluationstudiesconductedtodate,andtoshedlightonwhatfactorsdetermineawetland’svalue.Wemaintainanassumptionthatthereexistsanunobservedvaluationfunctionthatdeterminesawetland’svaluegivenitsphysi-cal,economicandgeographiccharacteristics.Af-terreviewing46studies,datafrom39wetlandvaluationstudieswereidentifiedthathadsuffi-cientcommonaltiestoallowinter-studycompari-sons.Weusedtwotechniquestolearnaboutthevaluationfunction,bothofwhichcanbebroadlydescribedasmeta-analysissincemanystudiesareusedtoidentifygeneralrelationships.Thefirstmethodthatweemployusesbivariategraphicalandstandardtechniques.Thisgivesusbothanindicationoftheextenttowhichparticularchar-acteristicsinfluencewetlandvalueswhilealsopor-trayingthefulldistributionofthedata.Thesecondtechniqueismorestandard,usingamulti-variateregressionofwetlandvaluesonthechar-acteristicsofboththewetlandsandthestudies.Together,thesetwotechniquesprovidearicherbasisfromwhichwecandrawlessonsonthefactorsdeterminingwetlandvalue.Therearenumerousreasonswhyunderstandingthevalueofwetlandservicesmightbeuseful.Themostobviousisthatifthevalueoftheseserviceswereknown,benefitstransfereffortscouldbesubstantiallyimproved.AsDeckandChestnut(1993)pointout,benefitstransfermayplayavarietyofdifferentroles,rangingfromanattempttoplaceaprecisevalueonaparticularresourcetoprovidinginformationthatfeedsintotheprocessofbuildingsupportforprojectsalreadyimple-mented.Whilebenefitstransferisrarelysuitablefortheformercase,itmightoftenbeappropriateforthelatter.Anotherformofbenefitstransferistheuseofestimatedvaluestopredicttheaggre-gatevalueofsimilarsystemsnationallyorglobally.Suchestimatescanbeusefulinsettingnationalprioritiesortheevaluationofpolicieswithimpactsthatarenationalorglobal.Costanzaetal.(1997),forexample,placedavalueontheentireglobe’secosystems.Whilesuchexpansiveeffortsmaybeoverambitious,theaggregatenum-bersdohelptogettheattentionofpolicymakersandthepublic.Estimatesofthevalueofawetlandcanalsoinfluencesite-specificvaluationeffortsintwoways.First,theymightprovideBayesianpriorsthatmightbeformallyincorporatedintothevalu-ationexercise.Secondly,theymaygivere-searchersasenseofwherethevaluesatstakearelikelytobeofgreatestsocialimportanceandmight,therefore,influencewheredetailedstudiesarecarriedout.Thepaperisorganizedasfollows.Inthenextsectionweprovideabriefoverviewoftheeco-nomicsofwetlandvaluation.Wesurveytheeco-logicalfunctionsandeconomicservicesprovidedbytheseareas,thebasisfortheirvaluationandthetechniquesthatareusedtoplaceaneconomicvalueonwetlands.Section3providesabriefsummaryofmeta-analysisasatool.InSections5and6weexplorethetrendsinthedata,identify-ingthesourcesofvariabilityinwe
本文标题:Theeconomicvalueofwetlandservicesametaanalysis
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