9unit13Endangered speciesWord文档下载推荐.docx

9unit13Endangered speciesWord文档下载推荐.docx

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CriticallyEndangered

Endangered

Vulnerable

Lowerrisk

ConservationDependent

NearThreatened

LeastConcern

Seealso

WorldConservationUnion

IUCNRedList

Anendangeredspeciesisapopulationofanorganismwhichisatriskofbecomingextinctbecauseitiseitherfewinnumbers,orthreatenedbychangingenvironmentalorpredationparameters.Anendangeredspeciesisusuallyataxonomicspecies,butmaybeanotherevolutionarysignificantunit.TheWorldConservationUnion（IUCN）hascalculatedthepercentageofendangeredspeciesas40percentofallorganismsbasedonthesampleofspeciesthathavebeenevaluatedthrough2006.[2]（Note:

theIUCNgroupsallthreatenedspeciesfortheirsummarypurposes.）Manynationshavelawsofferingprotectiontothesespecies:

forexample,forbiddinghunting,restrictinglanddevelopmentorcreatingpreserves.Onlyafewofthemanyspeciesatriskofextinctionactuallymakeittothelistsandobtainlegalprotection.Manymorespeciesbecomeextinct,orpotentiallywillbecomeextinct,withoutgainingpublicnotice.

Conservationstatus

Theconservationstatusofaspeciesisanindicatorofthelikelihoodofthatendangeredspeciesnotliving.Manyfactorsaretakenintoaccountwhenassessingtheconservationstatusofaspecies;

notsimplythenumberremaining,buttheoverallincreaseordecreaseinthepopulationovertime,breedingsuccessrates,knownthreats,andsoon.TheIUCNRedLististhebestknownconservationstatuslisting.

Internationally,190countrieshavesignedanaccordagreeingtocreateBiodiversityActionPlanstoprotectendangeredandotherthreatenedspecies.IntheUnitedStatesthisplanisusuallycalledaspeciesRecoveryPlan.

IUCNRedListEndangeredspecies

EndangeredspeciesundertheIUCNRedListreferstoaspecificcategoryofthreatenedspecies,andmayincludecriticallyendangeredspecies.

IUCNRedListofThreatenedSpeciesusesthetermendangeredspeciesasaspecificcategoryofimperilment,ratherthanasageneralterm.UndertheIUCNCategoriesandCriteria,endangeredspeciesisbetweencriticallyendangeredandvulnerable.Alsocriticallyendangeredspeciesmayalsobecountedasendangeredspeciesandfillallthecriteria

ThemoregeneraltermusedbytheIUCNforspeciesatriskofextinctionisthreatenedspecies,whichalsoincludestheless-at-riskcategoryofvulnerablespeciestogetherwithendangeredandcriticallyendangered.

IUCNcategoriesinclude:

∙Extinct:

thelastremainingmemberofthespecieshasdied,orispresumedbeyondreasonabledoubttohavedied.Examples:

Thylacine,Dodo,PassengerPigeon

∙Extinctinthewild:

captiveindividualssurvive,butthereisnofree-living,naturalpopulation.Examples:

SouthChinaTiger,AlagoasCurassow

∙Criticallyendangered:

facesanextremelyhighriskofextinctionintheimmediatefuture.Examples:

ArakanForestTurtle,JavanRhino,BrazilianMerganser

∙Endangered:

facesaveryhighriskofextinctioninthenearfuture.Examples:

BlueWhale,SnowLeopard,AfricanWildDog,Tiger,Albatross,CrownedSolitaryEagle

∙Vulnerable:

facesahighriskofextinctioninthemedium-term.Examples:

Cheetah,Gaur,Lion,Wolverine

∙ConservationDependent:

Thefollowinganimalisnotseverelythreatened,buttheanimalmustdependonconservationprograms.Examples:

SpottedHyena,LeopardShark,BlackCaiman

∙NearThreatened:

maybeconsideredthreatenedinthenearfuture.Examples:

Blue-billedDuck,SolitaryEagle,Small-clawedOtter,ManedWolf

∙LeastConcern:

noimmediatethreattothesurvivalofthespecies.Examples:

BrownRat,NootkaCypress,WoodPigeon

UnitedStates

"

Endangered"

inrelationto"

threatened"

undertheESA.

UndertheEndangeredSpeciesActintheUnitedStates,"

endangered"

isthemoreprotectedofthetwocategories.TheSaltCreektigerbeetle（Cicindelanevadicalincolniana）isanexampleofanendangeredsubspeciesprotectedundertheESA.

IntheUnitedStatesalone,the“numberofknownspeciesthreatenedwithextinctionistentimeshigherthanthenumberprotectedundertheEndangeredSpeciesAct”（Wilcove&

Master,2008,p.414）.TheUSFishandWildlifeServiceaswellastheNationalMarineFisheriesServiceareheldresponsibleforclassifyingandprotectingendangeredspecies,yet,addingaparticularspeciestothelistisalong,controversialprocessandinrealityitrepresentsonlyafractionofimperiledplantandanimallife（Wilcove&

Master,2008,p.414）.

Someendangeredspecieslawsarecontroversial.Typicalareasofcontroversyinclude:

criteriaforplacingaspeciesontheendangeredspecieslist,andcriteriaforremovingaspeciesfromthelistonceitspopulationhasrecovered;

whetherrestrictionsonlanddevelopmentconstitutea"

taking"

oflandbythegovernment;

therelatedquestionofwhetherprivatelandownersshouldbecompensatedforthelossofusesoftheirlands;

andobtainingreasonableexceptionstoprotectionlaws.

Beinglistedasanendangeredspeciescanhavenegativeeffectsinceitcouldmakeaspeciesmoredesirableforcollectorsandpoachers.[3]Thiseffectispotentiallyreducible,suchasinChinawherecommerciallyfarmedturtlesmaybereducingsomeofthepressuretopoachendangeredspecies.[4]

Anotherproblemwithlistingspeciesisitseffectofincitingtheuseofthe"

shoot,shovel,andshut-up"

methodofclearingendangeredspeciesfromanareaofland.Somelandownerscurrentlymayperceiveadiminutioninvaluefortheirlandafterfindinganendangeredanimalonit.Theyhaveallegedlyoptedtosilentlykillandburytheanimalsordestroyhabitat,thusremovingtheproblemfromtheirland,butatthesametimefurtherreducingthepopulationofanendangeredspecies.[5]TheeffectivenessoftheEndangeredSpeciesAct,whichcoinedtheterm"

endangeredspecies"

hasbeenquestionedbybusinessadvocacygroupsandtheirpublications,butisneverthelesswidelyrecognizedasaneffectiverecoverytoolbywildlifescientistswhoworkwiththespecies.Nineteenspecieshavebeendelistedandrecovered[6]and93%oflistedspeciesinthenortheasternUnitedStateshavearecoveringorstablepopulation.[7]

Currently,1,556knownspeciesintheworldhavebeenidentifiedasendangered,ornearextinction,andareunderprotectionbygovernmentlaw（Glenn,2006,Webpage）.Thisapproximation,however,doesnottakeintoconsiderationthenumberofspeciesthreatenedwithendangermentthatarenotincludedundertheprotectionofsuchlawsastheEndangeredSpeciesAct.AccordingtoNatureServe’sglobalconservationstatus,approximatelythirteenpercentofvertebrates（excludingmarinefish）,seventeenpercentofvascularplants,andsixtoeighteenpercentoffungiareconsideredimperiled（Wilcove&

Master,2008,p.415-416）.Thus,intotal,betweensevenandeighteenpercentoftheUnitedStates’knownanimals,fungi,andplantsarenearextinction（Wilcove&

Master,2008,p.416）.ThistotalissubstantiallymorethanthenumberofspeciesprotectedundertheEndangeredSpeciesActintheUnitedStates,whichmeansnumerousspeciesareinchingcloserandclosertowardextinction.

Questionofethics

Eveninthesearchtolearnmoreaboutthesespecies,manyecologistsdonottakeintoconsiderationtheimpacttheyleaveontheenvironmentanditsinhabitants.Itisapparentthatthe“questforecologicalknowledge,whichissocriticalforinformingeffortstounderstandandconserveEarth’sbiodiversityalongwithvaluedecosystemgoodsandservices,frequentlyraisescomplexethicalquestions”,[8]andthereisnoclearwaytoidentifyandresolvetheseissues.Environmentaliststendtofocusonthewholeecologicalsphereinsteadofthewelfareofindividualanimals.Focusingonsuchabroadviewtendstodiminishthevalueofeachindividualcreature.“Biodiversityconservationiscurrentlyaprinciplegoalforresourcemanagementof11.5%oftheworld’ssurfacearea.”[9]Largeportionsoflifeoccuroutsidetheseprotectedareasandmustbetakenintoconsiderationiftheconservationofendangeredspeciesisgoingtobeeffective.

Impactonbiodiversityandendangeredspecies

Inordertoconservethebiodiversityoftheplanet,onemusttakeintoconsiderationthereasonswhysomanyspeciesarebecomingendangered.“HabitatlossisthemostwidespreadcauseofspeciesendangermentintheU.S.,affecting85%ofimperiledspecies”（Wilcove&

Master,2008,p.416）.Whenananimal’secosystemisnotmaintained,theylosetheirhomeandareeitherforcedtoadapttonewsurroundingsorperish.Pollutionisanotherfactorthatcausesmanyspeciestobecomeendangered,especiallyalargeproportionofaquaticlife.Also,overexploitation,disease（Wilcove&

Master,2008,p.416）,andclimatechange（Kotiahoetal.,2005,p.1963）haveledtotheendangermentofseveralspecies.

However,themostimportantfactorleadingtotheendangermentofthemajorityofwildlifeintheworldisthehumanimpactonthespeciesandtheirenvironment.“Ashumanuseofresources,energy,andspaceintensifiedoverthepastfewcenturies,thediversityoflifehasbeensubstantiallydiminishedinmostpartsoftheworld”（Ishwaran&

Erdelen,2006,p.179）.Basically,asthehumanimpactontheenvironmentincreases,thediversityoflifedecreases.Humansareconstantlyusingtheresourcesandspaceofotherspeciesforthemselves,negativelyimpactingthesurvivalrateofmanycreatures.

Humanshavealsosetstandardsforwhichspeciestheythinkshouldbesavedandwhichspeci