Longtermmonitoringofwetlandusinglandsatnastersatel

JournalforNatureConservation19(2011)215–223ContentslistsavailableatScienceDirectJournalforNatureConservationjournalhomepage::AmvrakikosGulf(Greece)LiesbethBortelsa,JonathanC.-W.Chanb,∗,RonnyMerkena,NicoKoedamaaLaboratoryforPlantBiologyandNatureManagement(APNA),VrijeUniversiteitBrussel,Pleinlaan2,B-1050Brussels,BelgiumbCartographyandGISResearchGroup,GeographyDepartment,VrijeUniversiteitBrussel,Pleinlaan2,B-1050Brussels,BelgiumarticleinfoArticlehistory:Received5April2010Receivedinrevisedform20December2010Accepted19January2011Keywords:LandsatASTERCoastalwetlandsChangedetectionFragmentationStopoverhabitatLong-distancemigratorywaterbirdsabstractThewestcoastofGreeceisanimportantmigrationrouteformigratorywaterbirds.Thewetlandsalongthiscoastareimportantstopoversitesduringbirdmigrationbetweenwinteringandbreedingsites.Theuseofremotesensingmethodsformappingbirdmigrationhabitatsandfortemporalmonitoringofchangesinthesehabitatswasinvestigated.TheAmvrakikosGulf,acoastalwetlandcomplexalongthewestcoastofGreece,wasselectedasthestudyarea.LandsatTMandETM+imagesandASTERVNIRimageswereusedtoperformapost-classificationchangedetectionoveratimeperiodof15years(1989–2004).Inordertoassessthespatialqualityofexistingwetlandpatches,spatialmetrics(suchaspatcharea,distancebetweenthepatches,andproximity)werecalculated.Tostudychangesinthedegreeoffragmentationofthestopoverarea,abinarypatchstructurewasusedinwhichthefocalpatcheswereembeddedinaneutralmatrix.TheresultsshowedthatLandsatandASTERVNIRsatelliteimagescanbeusedtotracesmallwetlandsofapproximately0.5haminimum.Thesedatasourcesaresuitableformonitoringchangesinwetlands,inparticularmarshesandmudflats,whichareimportanthabitatsformigratorywaterbirds.Inthe15-yearperiodthathasbeenstudiedtherewasanestimated32%decreaseinmarshandmudflatarea.Amongthisdecrease,25%wenttowatersurfaceand7%tovegetationinthemonthsofAugustandSeptember.Withinthesameperiodoftime,ahigherdegreeoffragmentationofthepotentialbirdmigrationhabitathasalsobeenrecorded.Forthispurpose,theremotesensingapproachusedinthisstudywherechangedetectionisperformedonfreelyavailableLandsatandASTERsatelliteimagescouldbeaninterestingtoolforpolicymakersandmanagers,astheyalloweasyrecognitionandmonitoringofchangesinwetlandsandthereforecontributetoanevaluationoftheefficiencyofprotectionandmanagementschemesappliedbycountriesfortheirwetlands.©2011ElsevierGmbH.Allrightsreserved.IntroductionMigratorywaterbirdsdependonsuitablewetlandareasalongtheirmigrationroutesasassemblyandstaging(orstopover)areas(deKlemm1994).Duringmigration,theytendtobegregariousinrelativelysmallareasforbriefperiodsoftime(Myersetal.1987)andmigrationsuccessdependsonintactmigratoryrouteswiththeavailabilityofcertainkeyfoodresourcesandrestingoppor-tunitiesatthesestopovers(Mooreetal.2005).Inordertoprotectmigrantssuccessfully,itisnecessarytopreserveessentialhabitatsinallpartsofanintegratedspeciesrange.However,itisestimatedthatapproximatelyhalfofallEuropeanwetlandswhichexistedinthelastcenturyhavenowbeenlostduetoagriculturalactivities,urbanexpansionandvariousmanagementpractices(EuropeanCommission2007).ForGreece,lossofwetlandsisestimatedat63%∗Correspondingauthor.E-mailaddress:[e-mail](J.C.-W.Chan).between1950and1985(EuropeanCommission2007).Asubstan-tialportionofthosearelocatedwithincoastalregionsrelatedtobirdmigratingroutes.ItisnotsurprisingthenthatmanywaterbirdpopulationsinWesternEurasiaandAfricaremaininlong-termandconsiderabledecline,sincewetlandlossanddegradationcontinuetobethemaincauseforthesepopulationchanges,probablynowbeingexacerbatedbysevereandprolongeddroughtsandotherimpactsofclimatechange(Davidson&Stroud2006).Aflyway-scaleanalysisforAfrican-WesternEurasianwadersshowedthat65%ofpopulationsweredecreasingintheBlackSea/MediterraneanFly-way(InternationalWaderStudyGroup2003;Stroudetal.2004,2006).GreeceispartoftheBlackSea/Mediterraneanflyway(Davidson&Stroud2004),oneofthethreemainshorebirdflywaysoverEurope.AndthemigrationrouteinGreecethatcoversthewest-erncoastlineismostimportant(Dimakietal.2006).AlthoughmanyofthewetlandsalongthiscoastareprotectedasRamsarsites,ImportantBirdAreas(IBAs),Natura2000sites,GreekNationalParks,etc.,manyoftheneededprotectionmeasuresarenotimple-1617-1381/$–seefrontmatter©2011ElsevierGmbH.Allrightsreserved.doi:10.1016/j.jnc.2011.01.004216L.Bortelsetal./JournalforNatureConservation19(2011)215–223mentedandtherearecasesofevidentdeterioration(Bazigou2007).Wetlandsarenotonlyecologicallyfragile;theirlocationusuallyputsthemattheforefrontofconflictwithhumanprioritiesoflanduse(airports,tourisminfrastructure,windenergyturbines,harbours...).Appropriateandeffectivemanagementisthekeyfactorfortheirsuccessfulconservation(Gerakis1992).AccordingtotheBirdDirective(2009/147/EC)effectivebirdprotectionisatrans-frontierenvironmentproblementailingcommonresponsi-bilities.TheCounciloftheEuropeanCommunities(2009).Measuresmustbetakenconcerningthediversityandareaofhabitatsofmigrato