.TheScienceoftheTotalEnvironment240199931]40Ecologicalissuesrelatedtowetlandpreservation,restoration,creationandassessmentDennisF.WhighamUSmithsonianEn¨ironmentalResearchCenter,Box28,Edgewater,MD21037,USAReceived15May1999;accepted18May1999Abstract.Awiderangeoflocal,state,federal,andprivateprogramsareavailabletosupportthenationalUSApolicyofwetland‘NoNetLoss’.Implementationofprograms,however,hasresultedinthecontinuedlossofnaturalwetlandsonthepremisethatrestoredorcreatedwetlandswillreplacethefunctionsandvalueslostbydestructionofnaturalwetlands.Whataretheecologicalimplicationsandconsequencesoftheseprogramsfromabiodiversityandecosystemperspective?Fromabiodiversityperspective,ongoingwetlandprotectionpoliciesmaynotbeworkingbecauserestoredorcreatedwetlandsareoftenverydifferentfromnaturalwetlands.Wetlandprotectionpoliciesmayalsobeinadequatetopreserveandrestoreecologicalprocessessuchasnutrientcyclingbecausetheymostlyfocusonindividualwetlandsandignorethefactthatwetlandsareintegralpartsoflandscapes.Wetlandmitigationprojects,forexample,oftenresultintheexchangeofonetypeofwetlandforanotherandresultinalossofwetlandfunctionsatthelandscapelevel.Themoststrikingweaknessinthecurrentnationalwetlandspolicyisthelackofprotectionfor‘dry-end’wetlandsthatareoftenthefocusofdebateforwhatisandwhatisnotawetland.Fromanecologicalperspective,dry-endwetlandssuchasisolatedseasonalwetlandsandriparianwetlandsassociatedwithfirstorderstreamsmaybethemostimportantlandscapeelements.Theyoftensupportahighbiodiversityandtheyareimpactedbyhumanactivitiesmorethanothertypesofwetlands.Thefailingsofcurrentwetlandprotectionandmitigationpoliciesarealsodue,inpart,tothelackofecologicallysoundwetlandassessmentmethodsforguiding.decisionmakingprocesses.TheecologicallybasedHydrogeomorphicHGMapproachtowetlandassessmenthasthepotentialtobeaneffectivetoolinmanagingbiodiversityandwetlandecosystemfunctioninsupportofthenational‘NoNetLoss’policy.PublishedbyElsevierScienceB.V.Keywords:Wetlands;Biodiversity;Ecosystemfunction;‘NoNetLoss’;Wetlandpolicy;Restoration;Creation;Mitigation;Assessment;Hydrogeomorphic;HGM;LandscapeTel.:q1-410-798-4424,ext.226;fax:q1-301-261-7954.U.E-mailaddress:whigham@serc.si.eduD.F.Whigham0048-9697r99r$-seefrontmatterPublishedbyElsevierScienceB.V..PII:S0048-96979900321-6()D.F.WhighamrTheScienceoftheTotalEn¨ironment240199931]40321.IntroductionMosthistoricalwetlandlossesthathaveoc-curredintheUSresulteddirectlyorindirectlyfromprogramssupportedbygovernmentpolicy.OnlyinrecentdecadeshavepolicydebatesandadministrativeprogramsresultedinasignificantdecreaseintherateofwetlandlossDahletal.,1991;DahlandAllord,1996;Opheim,1997;.Tzoumis1998.Insomestatese.g.Ohioand.California,protectionandrestorationeffortscameonlyaftermostwetlandswereloste.g...Sibbing,1997.Inotherstatese.g.Florida,his-toricalpoliciesrelatedtowaterandwetlandman-agementresultednotonlyinconsiderablewet-landlosses,but,inthreatstoentirelandscapes.InsouthFlorida,forexample,theEvergladesandotherhydrologicallylinkedecosystemsarethreat-enedprimarilybecauseofhistoricalpoliciesthatallowedwidespreadwetlandconversionandalter-ationoflocalandregionalhydrologicregimes.Gundersonetal.,1995;Harwell,1997.Cur-rently,mosttypesofwetlandsareprotectedthroughavarietyoffederalandstateprograms.VottlerandMuir,1996andsomeprogramse.g..WetlandsPreserveProgramprovidefundingtosupportwetlandprotectionandrestoration.Wearecurrentlyintheeraof‘NoNetLoss’.Somearguethatwehaveachievedthegoalof‘NoNetLoss’ofwetlandsbecausetherateofwetlandlosshasslowedandbecausemanywetlandsare.beingrestoredorcreatede.g.Tolman,1997.Othersarguethat,whilewetlandlosseshaveslowed,wetlandslossescontinueatanunaccept-.ablerateHeimlichetal.,1997.Thedebaterelatedto‘NoNetLoss’ismostoftenanumbersgameandwhatisusuallylostinthedebateisthefactthatwetlandscontinuetobelostordegradedandwetlandsdesignedtoreplacetheme.g.re-.stored,enhanced,orcreatedwetlandsoftenhavelowerbiodiversityanddonotfunctionsimilarlyto.thenaturalwetlandsKentula,1996;Street,1998.Manywetlands,andthefunctionsthattheyper-form,aregoneforeverbecausealargenumberofwetlandlossesareneverreportedandrestorationprojectsareoftennevercompletedorarefailures.Smith,1997.ThescenariothatemergesisoneinwhichtheUScontinuestolosenaturalwetlandswithoutseriouslyconsideringtheimpactsofthelossesundertheguiseofthe‘NoNetLoss’policy.Oneconsequenceofcontinuedwetlandlosses,asdescribedbelow,isthattheywillhaveanegativeimpactonwetlandassociatedspecies.Wetlandlosscanbeviewedinseveralways.Themostobvioustypeofwetlandlossistheconversionofajurisdictionalwetlandtoanon-jurisdictionalstatus.Someareasmaybeclassifiedaswetlandsbasedonbiota,soils,andhydrologybutarenotconsideredtobejurisdictionalbe-causetheyarespecificallyexcludedbystateorfederalregulations.Conversionofthesetypesofwetlandsalsorepresentsawetlandloss.Finally,itcouldbearguedthatconversionofonetypeofwetlandtoanotherrepresentsanetlossofwet-lands.Thepointthatneedstobemade,indepen-dentofhowonedefineswetlandloss,isthatwetlandlossescontinueformanyreasons.InMinnesotaadequatewetlandlegi