AlotoftreesaredyinginAfrica'sSahelregionandnewstudysaysclimatechangecausedbyhumansistoblame.What'smore,manytreespeciesarealsodisappearing.ThestudyappearsintheJournalofAridEnvironments.ClimatechangescientistPatrickGonzalezledtheresearchonsixcountries.Atthetimeofthestudy,GonzalezwasavisitingscholarattheCenterforForestryattheUniversityofCaliforniaatBerkeley."WeconductedourresearchintheAfricanSahel,anaridregionontheedgeoftheSaharawherepeopledependontreesforsurvival.AndtheSahelhasexperiencedthemostseveredroughtintheworldinthemodernrainfallmeasurementrecord,"hesaid.DryingupTheresearchshowsthatduringthe20thCenturyrainfallintheSaheldroppedbetween20and30percent."Oneinsixtreesdiedinthelasthalfofthe20thCenturyand,second,oneinfivetreespeciesdisappearedlocally.Andthenthird,togetherthesechangesshiftedvegetationzonessouthwardtowardareasofmorerainfall,"hesaid.Possiblecausesofthevegetationshiftincludedecliningrainfall,growinghumanpopulationanddecreasingsoilfertility."Ourstatisticalcomparisonshowedthatclimateoutweighedtheotherfactors.So,climatechangewasthemaincauseofthelossofthetrees.ClosertotheSaharayouhavearidzonetreeslikeAcaciawiththorns.Verydrytrees.AndthenasyoumovefarthersouthtowardstheEquator,youhavespeciesthathavefruitsandhardwoodandspeciesthatrequiremorerainfall,thatrequiremoisterconditions,"hesaid.ThestudyblamestheclimatechangeintheSahelonmotorvehicleandpowerplantemissionsandotherhumanactivityovertheyears.GonzalezdescribedconditionsneartheSaharaaslong-termlanddegradation."Soweactuallyareshowingaformofdesertification.Desertificationislanddegradation.We'renotshowingashiftofthesandsoftheSahara,butwhatweareshowingisadegradationfarsouthoftheSaharawithintheSahelwithintheSudan,withinGuinea.ThosearethezonessouthoftheSahara,"hesaid.Adapting,avertingLocalpopulationsintheregionhaverootsgoingbackmorethanathousandyearsandrelocatingisnotanoption.Indigenouspeopleareadaptingtoclimatechange,forexample,bycaringforandpruningsmalltreesuntilthey'remature.Suchapracticecanhelpdoubletreedensityinafield.However,Gonzalezsaidlocalpopulationscannotaddressclimatechangebythemselves.Hesaystheinternationalcommunitymustact."TheIntergovernmentalPanelonClimateChange–that'sthetopscientificpanelthatexaminesclimatechangeandIsitonthatpanel–hasshownthatwe,intheUnitedStates,andotherindustrializednationshaveitinourpowerusingcurrenttechnologiesandpracticestoavertmoredrasticimpactsaroundtheworldbyreducingourgreenhousegasemissions,"hesaid.GonzalezwasjoinedintheresearchbyComptonTucker,seniorearthscientistatNASA'sGoddardSpaceFlightCenterandHamadySy,Mauritania'scountryrepresentativeattheFamineEarlyWarningSystemsNetwork.BothNASAandtheU.S.GeologicalSurveyprovidedfundingforthestudy.
