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（每日一读）2014年高考英语8月考前突破阅读理解能力文化教育偷猎死亡的非洲大象数量达到临界值素材.doc

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偷猎死亡的非洲大象数量达到临界值 Africa'selephantshavereachedatippingpoint:morearebeingkilledeachyearthanarebeingborn,astudysuggests. 研究显示，非洲大象的数量已达临界值：每年被猎杀的大象比出生的大象都要多。 Researchersbelievethatsince2010anaverageofnearly35,000elephantshavebeenkilledannuallyonthecontinent. Theywarnthatiftherateofpoachingcontinues,theanimalscouldbewipedoutin100years. TheworkispublishedintheProceedingsoftheNationalAcademyofSciences. LeadauthorGeorgeWittemyer,fromColoradoStateUniversity,said:"Weareshreddingthefabricofelephantsocietyandexterminatingpopulationsacrossthecontinent." Dramaticloss Theillegaltradeinelephanttuskshassoaredinrecentyears,andakilogramofivoryisnowworththousandsofdollars.MuchofthedemandhasbeendrivenbyarapidlygrowingmarketinAsia. Whileconservationistshavelongsaidtheoutlookwasbleak,thisstudyprovidesadetailedassessmentoftheimpactthisishavingonAfrica'selephants. Theresearchershavefoundthatbetween2010and2013,Africalostanaverageof7%ofitsentireelephantpopulationeachyear. Becauseelephantbirthsboostthepopulationbyabout5%annually,thismeansthatoverallmoreoftheanimalsarebeingkilledthanarebeingborn. JulianBlanc,whoalsoworkedonthestudy,fromtheConventiononInternationalTradeinEndangeredSpeciesofWildFaunaandFlora(Cites),said:"Ifthisissustained,thenwewillseesignificantdeclinesovertime. "Theotherthingtobearinmindisthatdifferentareasareaffecteddifferently. "TherearestillhealthygrowingpopulationsinpartsofAfrica,Botswanaforexample.Butinotherplacesthepoachinglevelsaredevastatinglyhigh,andthatisparticularlythecaseinCentralAfrica." InCentralAfricaitisestimatedthatelephantnumbershavefallenbyabout60%inadecade.