Earth en­ters sixth ex­tinc­tion phase

Ver­te­brates van­ish­ing 114 times faster than nor­mal; hu­mans un­der threat too

The Times of India (Mumbai edition) - - TRENDS TIMES -

With an­i­mals dis­ap­pear­ing about 100 times faster than they used to, the world has em­barked on its sixth mass ex­tinc­tion and hu­mans could be among the first vic­tims, said sci­en­tists in a re­port pub­lished in the Science Ad­vances jour­nal. Au­thored by sci­en­tists at Stan­ford, Prince­ton and Berke­ley univer­si­ties, the re­searchers found that ver­te­brates were van­ish­ing at a rate 114 times faster than nor­mal. And hu­mans are likely to be among the species lost. The study —which its au­thors de­scribed as “con­ser­va­tive” is based on doc­u­mented ex­tinc­tions of ver­te­brates, or an­i­mals with in­ter­nal skele­tons such as frogs, rep­tiles and tigers, from fos­sil records and other his­tor­i­cal data.

The causes of species loss ranges from cli­mate change to pol­lu­tion to de­for­esta­tion and more. “If it is al­lowed to con­tinue, life would take many mil­lions of years to re­cover and our species it­self would likely dis­ap­pear early on,” said lead au­thor Ger­ardo Ce­bal­los of the Uni­ver­si­dad Au­tonoma de Mexico. “We em­pha­size that our cal­cu­la­tions very likely un­der­es­ti­mate the sever­ity of the ex­tinc­tion cri­sis be­cause our aim was to place a re­al­is­tic lower bound on hu­man­ity’s im­pact on bio­di­ver­sity,” said the study.

The mod­ern rate of species loss was com­pared to the “nat­u­ral rates of species dis­ap­pear­ance be­fore hu­man ac­tiv­ity dom­i­nated.” It can be dif­fi­cult to es­ti­mate this rate, also known as the back­ground rate, since hu­mans don’t know ex­actly what hap­pened through­out the course of Earth’s 4.5 bil­lion year history. The re­search how­ever, found that that since 1900 more than 400 ver­te­brates have dis­ap­peared — an ex­tinc­tion rate 100 times higher than in other — non-ex­tinc­tion — pe­ri­ods. “There are ex­am­ples of species all over the world that are es­sen­tially the walk­ing dead. We are saw­ing off the limb that we are sit­ting on,” said Stan­ford Univer­sity pro­fes­sor Paul Ehrlich. Ac­cord­ing to the In­ter­na­tional Union for Con­ser­va­tion of Na­ture, about 41 per­cent of all am­phib­ian species and 26 per­cent of all mam­mals are threat­ened with ex­tinc­tion.

The last sim­i­lar event was 65 mil­lion years ago, when di­nosaurs dis­ap­peared, most prob­a­bly as a re­sult of an as­ter­oid. This time around the re­search, which mainly high­lights cli­mate change, pol­lu­tion and de­for­esta­tion as causes for the rapid change, notes that a knock-on ef­fect of the loss of en­tire ecosys­tems could be the pri­mary cause.

As our ecosys­tems un­ravel, the Cen­tre for Bi­o­log­i­cal Di­ver­sity has noted that we could face a “snow­ball” ef­fect whereby in­di­vid­ual species ex­tinc­tion ul­ti­mately fu­els more losses. The re­port, which builds on find­ings pub­lished by Duke Univer­sity last year, does note that avert­ing this loss is pos­si­ble through in­ten­si­fied con­ser­va­tion ef­fects to al­le­vi­ate the pres­sure on pop­u­la­tions of threat­ened species —no­tably habi­tat loss, over-ex­ploita­tion for eco­nomic gain and cli­mate change. But that “win­dow of op­por­tu­nity is rapid clos­ing.”

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