Animalsareconsideredtobeendangeredifthespeciesisclosetoextinctionthroughoutallormostofitsenvironment.Animalsbecomeendangeredforavarietyofreasons.

Someanimalsbecomeendangeredwhentheirhabitatscontainresourcesforhumans.Forexample,commercialforestcuttingintheAmazonRainforesthasseriouslyreducedthepopulationofmanyanimalspeciesandleadtotheextinctionofothergroups.Landitselfisanimportantresourcetohumanssinceitprovidesuswithlivingspace,andwhenpeoplereplaceanimalhabitatswithhumanhabitats,itcanleadtolargerlossofnaturalspecies.

Commercialandindustrialoperationsmayreducelandorwaterforanimalsandpollutetheirenvironment.Duetowaterpollution,thebaiji,afreshwaterdolphinnativetoChina,wasdeclaredextinct,meaningit’sunlikelythepopulationcanrecover.Evennoisepollutionfromhumanactivitiescanleadtothedisorderofanimalbehavior.

Anothercausethatmakesanimalsbecomeendangeredisover-fishingorover-hunting.Over-huntingwhalesledtonearextinctionofmanyspeciesofwhales.

Theintroductionofanon-nativespeciestoahabitatmaymakeanimalsbecomeendangered.Thenativespeciesmaynotdefendagainstanewone,andtheeffectscanbedangerous.InAustralia,theintroductionofthecommonhousecatledtotheextinctionofthered-frontedparakeetandhasseriouslydamagedthepopulationsofseveralsmallanimals.

Introducedspeciescanalsobringnewdiseaseswiththem.Asaresult,animalsbecomeendangered.Nativeanimalsmaynothavethepowertofightagainstnon-nativediseases,andpopulationlevelscansuffer.Anothercauseofdiseaseishuman-introducedchemicals.TheuseofDDTisbelievedtobeoneoftheleadingcausesindrivingtheCaliforniaCondortonearextinction.

Whenanimalsbecomeendangered,theentirefoodchaincanbeaffected.Forexample,in2008diseaseseriouslyharmedthehoneybee,whichislargelyresponsibleforpollinating(授花粉) plants,includingmanyfruitsandvegetables.Withouttheirpollination,averylargepartofthehumandietcouldbereduced.Infact,ifthehoneybeeshouldbecomeextinct,ourlifewouldbeaffectedandbillionsofdollarswouldbelost.Therefore,manypeoplearguethatwhenanim