Landscape-Metrics-as-Indicators-of-Disturbances-in

DownloadedAt:20:406May2008W32LandscapeMetricsasIndicatorsofDisturbancesinaBeach-DuneSystemANAFAGGI1,JOSEDADON2,PATRICIAPERELMAN1,ANDGABRIELAPOSSE31MACN-CONICET,BuenosAires,Argentina2FECYN-UBA,BuenosAires,Argentina3INIA,BuenosAires,ArgentinaInArgentina,morethan45%ofthepopulationissettleddownwithin100kmofthecoastexertingbiginfluenceonthelandscape.Theircorrectunderstandingisofcon-cern,especiallywhenaddressinglanduseplanningandconservation.Theoceaniccoastextendsalong4725kmbutonly800kmaresandybeachesanddunes,wherevacationresortsarelocated.Inourstudyweanalysechangesinthelandscapestruc-tureoftheAtlanticbeach-dunesystemcausedbyurbanisationinordertoidentifypat-ternsofchangesthatcanbeincorporatedintomodeldescribingcoastalresortsdevelopment.Ourhypothesisisthatlandscapemetricscanbeusedasindicatorsfornaturalandhumaninduceddisturbancesinabeach-dunesystem.Thestudyareacom-prises6sectorsalongtheAtlanticcoastofTheBuenosAiresprovincealongagradientofurbanisationdefinedbytheproportionoftheurbanisedareaineachsector.AlandcovermapforeachsectorwasobtainedusingthespectralinformationprovidedbyLandsatETM+images.Weperformedanunsupervisedclassificationwith20classeswithred,nearredandmidinfrared(spatialresolution30m).Theseclassificationsmapsweregroupedinto5newclasses:sandybeaches,vegetateddunes,forestations,denseurbanisationanddisperseurbanisation.Forthelandscapestructureanalysisweused:INUMP:Indexofnumberofpatches,MPSmeanpatchsizeinhectares,AWMSI:Areaweightedmeanpatchindexasanaveragematchadjustedperimeterarearatio.Itgivesanideaoftheshapecomplexity.AWMPFDAreaweightedmeanpatchfractaldimensiontomeasureshapecomplexity.Iftheshapeperimetersaresimplethisdimen-sionapproaches1.MNNMeannearestneighbourinmetersasameasureoftheopenspacebetweenpatchesandasestimationofpatchisolation.Numberandformofdunepatchescanbelinkedtomanpressure.Inmorepopulatedresortsthedunesshowsupe-riornumberofpatchesofsmallersize.ThiseffectiscoincidentwithdecreasingvaluesofAWMSI,indicativeofasimplificationofpatchshape.Thismeanssmaller(9.71–31,15ha)andmoreisodiametricpatches.Insomeresortsthedeleteriouseffectofurbanisationonvegetateddunesiscompensatedbytheprogradationofthedune-beachsystem.Atbothextremesoftheurbanisationgradient,patchesshowhigherval-uesofshapecomplexity.Thesecouldbeassociatedwiththeprocessofdunesbuildingwhichiswinddependent.Bytheurbanareastheutilisedmetricsexplainsettlementdif-ferencesamongresorts.ThedisperseurbanisationshowhighervaluesofAWMSIinsettlementswithleapfrogtowngrowth.TheindicatorMNNpointedouttomoreiso-lateddisperseurbanisation.Landscapemetricswerenotsensitiveenoughtodescribedifferencesbytheclassessandybeachandforestation.Thefirstisverymuchdepen-dentonwinddynamics,ageomorphologicprocessessentialinmaintainingtheland-scapeinitsdynamicphase.Forestationsfeaturesdependontheplantationactionscarriedonbymanineachresort.UEBI1555-52751555-5267EnvironmentalBioindicators,Vol.1,No.1,Feb2008:pp.0–0