Mapping Biodiversity in a Modified Landscape Charlotte Louise Owen
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Mapping biodiversity in a modified landscape Charlotte Louise Owen 2008 Athesissubmittedinpartialfulfilmentofthe requirementsforthedegreeofMasterofScienceandthe DiplomaofImperialCollegeLondon Contents Abstract 1 1. Introduction 2 1.1Conservationinmodifiedlandscapes 2 1.2Mapping biodiversityatthe landscapescale 2 1.3Projectaimsandobjectives 4 2. Background 5 2.1Betadiversity 5 2.2Characteristicsofmodifiedlandscapes 6 2.3Carabidsasa bioindicator 8 2.4Carabidsinmodifiedlandscapes 9 2.5Thestudysite 11 3. Methods 13 3.1Selectionofsamplingsites 13 3.2Fieldsampling 14 3.3Environmentalvariables 15 3.4Statisticalanalysis 15 3.4.1Diversityindices 15 3.4.2Fragmentationandedgeeffects 16 3.4.3Carabidspecies assemblages 17 3.4.4Modellingcarabiddiversityatthelandscapescale 17 i 4. Results 18 4.1Abundance 18 4.2Diversityandevenness 20 4.3Fragmentationeffects 21 4.4Edgeeffectsacross transects 22 4.5Carabidspecies assemblages 24 4.6Predictedspeciesdiversity 27 4.7Predictedbetadiversity–generalizeddissimilaritymodelling 27 5. Discussion 30 5.1Carabidspeciesdiversity,evennessandabundance 30 5.2Edgeeffects 31 5.3Carabidspecies assemblages 32 5.4Predictedspeciesdiversity 33 5.5Predictedbetadiversity 34 6. References 37 7. Acknowledgements 46 8. Appendix 47 ii Abstract Themajorityoftheworld’s biodiversityexistsoutside protectedareas,inlandscapes heavilymodifiedbyanthropogenic activity.Itis thereforenecessarytogaina better understandingoftherolethatmodifiedlandscapes playinthemaintenanceof biodiversity.Theapplicationofmethodsusedtoassessandprioritiseareasfor conservationatthe landscapescaleislimitedbytheavailabilityofadequatespecies distributiondata,a problemthatiscommonlysolvedbycombiningavailabledata withremotelysensedlandcovervariablesinordertoextrapolateestimatesofspecies richnessacrosstheregionofinterest.However,theconcepts ofcomplementarityand irreplaceabilityhavehighlightedthe needforanadditionalmeasuredescribingthe levelofcompositionaldissimilarity,or betadiversity,betweenlocations.Thisstudy aimstoinvestigatewhether patterns ofcompositionaldissimilaritycanbe modelled acrossa regioninasimilarfashiontoexistingmodelsofspeciesrichness. Theresponseofcarabidbeetles(Coleoptera:Carabidae)totheeffectsofhabitat modification,intheformofforestfragmentationandresultingedgeeffects,was investigatedinamodifiedlandscape inBerkshire,England.Resultsshowedno significantdifferenceincarabidspeciesdiversitybetweenhabitattypes buta significantincreaseincarabiddiversityandabundancewithincreasingfragmentarea. Edgeeffectshadasignificant impactoncarabidabundanceandcommunityevenness. Itwasfoundthatcarabidsformeddefinable assemblagesthatdifferedbyhabitattype andcouldbereliablypredictedusingremotelysensedlandcoverdata.Generalized dissimilarity modelling(GDM)wasusedtomodelandpredict patternsofcarabid compositionaldissimilarityatthe landscapescale,whichwerethenpresentedvisually asamap. 1 1. Introduction 1.1 Conservation in modified landscapes Anthropogenicimpacts ontheenvironmentare amajorcontributingfactortothe global lossof biodiversity(Vanbergen et al. 2005).Themostsignificantofthese impactsislandscapemodificationcausedbyincreasingurbandevelopmentandthe conversionofnaturalhabitatstoagriculture(Sala et al .2000,Wessels et al. 2000). Already,over36%oftheearth’ssurfacehas beenconvertedtoagricultureandintact ecosystemsare beingconvertedatratesofover1% peryear(Meir et al .2004).Atthe sametime,urbanisationisincreasingworldwide.Urbansprawlisexpandingthe extentofurbanboundaries,andurbanpopulationsare becomingmoredensely populatedatsucharatethatitis predictedthat theglobalurbanpopulationwillhave doubledby2025(Alaruikka et al .2002). Whilsttheglobalsystemof protectedareasmaysafeguardkeysitesfrom anthropogenicmodification,the proportionoftheearth’ssurfaceunder such protectionisestimatedat just12% (CBD2007).Themajorityoftheworld’s biodiversitymustthereforecoexist withhumanactivity.Consequently,itis necessaryto progress pastthe ‘protectionparadigm’andgaina betterunderstanding oftheroles playedbymodifiedlandscapesinthe maintenanceofnative biodiversity. Theseare likelytobe significant.Thenatureofthe‘matrix’ of modifiedland surroundingprotectedareasgreatlyaffectstheir effectiveness andconnectivity (Franklin1993).Thematrixitself providesimportanthabitat andecosystemservices (Meir et al .2004),whilstmanmade sites andurbangreen-areascanactasanalogues ofnaturalhabitatsandproviderefugiafor manyspecies,particularlyinvertebrates (Eversham et al .1996,Eyre et al .2003). 1.2 Mapping biodiversity at the landscape scale Methodsfortheassessmentandprioritizationofareasforconservationhave progressedrapidly,suchthatthere is nowahugerangeofsite-selectionalgorithms anddecisionsupportsoftwareavailableforconservationmanagersandurbanplanners 2 (Margules &Pressey2000).However,theapplicationofthesetoolsis limitedbythe availabilityofadequate speciesdistributiondata (Rodrigues &Brooks2007),whichis sparseat best,evenforwell-knowntaxasuchas birdsandmammals(Sarkar et al . 2006).It is usuallyinfeasible toremedythesituationbyconductingdetailedfield surveys,sincetheyareexpensive,time-consumingandbear highopportunitycosts, giventhatanyresourcesspentonidentifyingpriorityareas cannot beusedforactive conservation management(Ewers et al .2005). Acommonalternativestrategyis tomakeuseof biodiversity‘surrogates’,or ‘indicators’.Theseareentitieswhosedistributionisknownandlikelytocorrelate wellwithspatial patternsof biodiversityas awhole(Margules&Pressey2000). Recentadvancesinremotesensingandgeographical informationsystems(GIS)have ledtothewideavailabilityofdetailedlandcover mapsatthefinespatialscales necessaryforregionalconservationplanning(Cowley et al .2000,Turner et al .2003). Itis thereforeeasytosamplelandscapevariables,suchasvegetationtypeorclimate, thatmayactasgoodsurrogates (Ferrier et al. 2007).Studieshaveestablishedstrong correlations betweenlandscapediversityandthe diversityof plants,invertebratesand birds(Ewers et al .2005).Itis thenpossible tomodelspecies presence,or abundance, asafunctionoflandscapevariables,andtoextrapolatespeciesdistributionsacross the regionofinterest.This providesgeographicallycompleteinformationfor conservation planningandotherenvironmentalapplications (Guisan&Zimmermann 2000). Modellingindividual speciesdistributionsisexpensiveandtime-consumingandis onlypossibleforwell-studiedspecieswithsufficientdistributionaldata(Ferrier 2002).Forthesereasons,itismoreoftenthecollective,oremergent propertiesof biodiversitythataremodeled,suchasspecies richness(Ferrier et al .2007).Models ofspeciesrichnesshave beenappliedattheglobalscaletoidentifybiodiversity ‘hotspots’richintotalspeciesorrarespecies(Grenyer et al .2006,Fa&Funk2007, Myers et al .2000,Olson&Dinerstein2002).Whilst species richness providesan importantmeasureofalphadiversity,itisoflimitedvalue toconservationplanningat finerspatial scales.The conceptsof complementarityandirreplaceabilityhave highlightedtheneedforanadditionalmeasuredescribingthe levelofcompositional dissimilarity,or betadiversity,betweenlocations (Margules &Pressey2000,Ferrier 3 et al .2007).Decisionsaboutwheretofocusconservationeffortaretherefore based onthe relative,ratherthantheabsolute,biodiversityvalueoflocations. 1.3 Project aims and objectives Thisstudywillassessthedegree towhichremotelysenseddatacanbe usedin combinationwithbiologicalsurveydatainorder toidentifypriorityareasfor conservation.Itaimsto: 1) Investigate whether patternsof beta diversitycanbemodelledacross aregion inasimilarfashiontoexistingmodelsofspeciesrichness; 2) Investigatetheinfluenceofanthropogenichabitatmodificationonlocal biodiversity; 3) Assesstheconservationvalueofamodifiedlandscape. Thestudywillsamplethegroundbeetlefauna (Coleoptera: Carabidae) ofa modified landscapeinBerkshire,England.Themainobjectivesare: 1) Toidentifyandcharacterize patternsofcarabiddiversityatthelandscape scale; 2) Toinvestigatethe effectsofforestfragmentationoncarabiddiversity; 3) Toinvestigatethe spatial patternofcarabiddiversityalonganenvironmental gradient betweenforest andgrasslandhabitats; 4) Toproduce amapofgroundbeetle betadiversityfortheregion. 4 2. Background 2.1 Beta diversity Thesimplestmeasureofdiversityis species richness,orthe numberofspecies present inacommunity.Speciesrichnesscanbefurther split intothreemaincomponentsof diversity,whicharedescribedasalpha,orinventorydiversity(α),beta,or differentiationdiversity(β)andgamma,orregionaldiversity(γ). Betadiversityrepresents thespatialturnoverofspecies,andmeasures the numberof speciesnotsharedbetweentwoormorelocations(Koleff et al .2003,Lande1996). Foralandscapewithagivengammadiversity,as betadiversityincreases,individual locations become moredifferenttoeachotherandsorepresentasmaller proportionof theregion’s totalspeciesdiversity.Betadiversitytherefore representsthespatial patternofspecies turnoverinthelandscape. The principles behindmostapproachestoconservationplanning,suchas complementarityandirreplaceability,aredrivenbybetadiversity(Margules& Pressey2000).Beta-diversityisdeterminedbycomplexinteractions betweenspecies traitsandcharacteristics ofthe physicallandscapeand,asa result,capturesnotonly thevariationinspeciesdiversitybetweenlocations butalsothecorresponding variationinlandscapediversity,aswellastheunderlyingecologicalandevolutionary processescausingthisvariation(McKnight et al .2007).Theincorporationof measuresof betadiversityintothesite-selectionalgorithmsusedforregional conservation planningthereforeresultsintheimprovedrepresentationof biodiversity asawhole. Numerousmeasuresof betadiversityhave beenproposedandappliedtoarangeof conservationissues,inparticularthe