Arapidassessmentmethodforcouplinganthropogenicstre

EcologicalIndicators13(2012)284–293ContentslistsavailableatScienceDirectEcologicalIndicatorsjournalhomepage:∗,W.N.Elleryb,D.M.Macfarlanec,G.P.W.JewittdaCentreforEnvironment,AgricultureandDevelopment,UniversityofKwaZulu-Natal,Pietermaritzburg,SouthAfricabDepartmentofEnvironmentalScience,RhodesUniversity,Grahamstown,SouthAfricacEco-PulseConsulting,Hilton,SouthAfricadSchoolofBioresourcesEngineeringandEnvironmentalHydrology,UniversityofKwaZulu-Natal,Pietermaritzburg,SouthAfricaarticleinfoArticlehistory:Received21June2010Receivedinrevisedform10June2011Accepted28June2011Keywords:WetlandecologicalconditionAssessmentHydrogeomorphicapproachCurrentconditionTrajectoryofchangeWET-HealthIndexSouthAfricaabstractSouthAfricafacesgrowingimpactsonwetlandsandlimitedresourcesforconductingassessments.Inresponse,amethodfortherapidassessmentofecologicalconditionbasedontheimpactsofhumanstressorsonhydrogeomorphicprocessesandvegetationresponseswasdeveloped.Therapidassess-mentmethod,referredtoasWET-Health,divideswetlandsintohydrogeomorphic(HGM)unitsthatareassessedindividually.Resultsarethencombinedintoacompositehealthscoreforthewetlandsystembeingevaluated.Deviationfromthenaturalreferenceconditionisexaminedforthreeseparatebutinter-linkedcomponentsofecosystemhealth:hydrology,geomorphologyandvegetation.ThespatialextentoftheHGMunitaffectedbyahumanimpactisestimatedandtheintensityoftheimpactintheaffectedareaisscoredonascaleof0(noimpact)to10(completetransformation)basedonpre-determinedindicatorsthatareratedusingclearscoringguidelines.Extentandintensityarecombinedtogiveanindexofthelevelofdeparturefromthenaturalreferencecondition.Anassessmentisalsomadeineachmoduleofthelikelytrajectoryofchangeofthewetland.Thispaperdescribesthemethodinordertoreflectonthecentralapproachandhighlightitsheuristicandhypothesisgeneratingvalue.©2011ElsevierLtd.Allrightsreserved.1.IntroductionWorldwide,wetlandscontinuetobesubjectedtoincreasinghumanimpactswhichdiminishtheirstateofhealthor“ecologicalcondition”(BrinsonandMalvarez,2002;Junk,2002).Highlev-elsofwetlanddegradationarereportedforSouthAfrica(Kotzeetal.,1995)suchthatthereisaneedfortoolstoassesstheeco-logicalconditionofwetlandsforarangeofpurposes,includingenvironmentalimpactassessments,ecologicalreservedetermina-tionsandtheplanningandmonitoringofwetlandmanagementandrehabilitationoutcomes.DeLeoandLevin(1997)indicatethatdecisionmakersrequiresimple,user-friendlyandcost-effectivetoolsthatenhanceecologicallysounddecisions.However,theyalsocautionthatintherushforsolutions,thecomplexityofnaturalsys-temstendstobeignored.Thechallengeisthereforetodevelopanapproachthatbalancestheeaseandspeedofuseofatoolwiththecomplexityanddetailthatitcaptures.Stirzakeretal.(2010)refertothisas“requisitesimplicity”.Anumberofmethods,particularlyintheUSA,havebeendevel-opedfortheevaluationofthefunctioningofwetlands,suchas∗Correspondingauthor.Tel.:[phone];fax:[phone].E-mailaddress:[e-mail](D.C.Kotze).Adamusetal.(1987),AmmannandStone(1991)andthehydroge-omorphic(HGM)method(Brinson,1993;BrinsonandRheinhardt,1996;Wardropetal.,2007).ManytoolsusingbioticindicatorsofwetlandhealthhavebeendevelopedsuchasthoseoftheUSEPA(2002a,b,c),Mack(2007)andMilleretal.(2006).TheconsiderablevariabilityoflandscapesandclimatesoversouthernAfricaman-ifestsinawiderangeofwetlandtypesandbiota(Rogers,1997;MucinaandRutherford,2006),whichcomplicatesthedevelopmentofbioticindicesthathaveapplicationacrosstheregion.StudiesofthebioticresponseofSouthAfricanwetlandstoimpactsareconfinedtoafewisolatedstudiesthatfocusonselectedtaxa(e.g.Bowdetal.,2006;Waltersetal.,2006).Giventhelackoffieldstud-ies,SouthAfricaisstillalongwayfromusingbioticindicesthataccountforitsdiversityofwetlandtypesandbiota.Inaddition,biotacanalsobetimeconsumingtodescribe,andrequireahighlevelofspecialistinput.Furthermore,oncedescribed,thebioticindicesoftendonotindicatethenatureofthehumanstressorsthathavecontributedtothedeclineinecologicalcondition,andthereforeprovidelittleinsightintomanagementrequirements.Inresponsetothesechallenges,arapidmethodforassessingecologicalconditionbasedontheimpactsofhumanstressorsonhydrogeomorphicprocessesandvegetationresponseswasdevel-opedforSouthAfrica,andisreferredtoasWET-Health(Macfarlaneetal.,2009).“Rapid”here,isdefinedasaprocessthattakesnomore1470-160X/$–seefrontmatter©2011ElsevierLtd.Allrightsreserved.doi:10.1016/j.ecolind.2011.06.023D.C.Kotzeetal./EcologicalIndicators13(2012)284–293285thantwopeoplehalf-a-dayinthefield,andthatrequiresnomorethananotherhalf-a-dayofofficepreparationanddataanalysistoobtainaresult(Fennessyetal.,2007).Forthispaper,ecologicalconditionisdefinedaccordingtotheecosystemintegritydefinitionofAnderson(1991)wheretheref-erenceconditionisanun-impactedconditioninwhichecosystemsshowlittleornoinfluenceofhumanactions.Itisneverthelessrec-ognizedthathumanshavelonginfluenceddisturbanceregimesinsouthernAfrica,andarethereforepartofthen