Sixth mass ex­tinc­tion has ar­rived: US study

The China Post - - FRONT PAGE -

The world is em­bark­ing on its sixth mass ex­tinc­tion with an­i­mals dis­ap­pear­ing about 100 times faster than they used to, sci­en­tists warned Fri­day, and hu­mans could be among the first vic­tims.

Not since the age of the di­nosaurs ended 66 mil­lion years ago has the planet been los­ing species at this rapid a rate, said a study led by ex­perts at Stan­ford Univer­sity, Prince­ton Univer­sity and the Univer­sity of Cal­i­for­nia, Berke­ley.

The study “shows with­out any sig­nif­i­cant doubt that we are now en­ter­ing the sixth great mass ex­tinc­tion event,” said co-au­thor Paul Ehrlich, a Stan­ford Univer­sity pro­fes­sor of bi­ol­ogy.

And hu­mans are likely to be among the species lost, said the study — which its au­thors de­scribed as “con­ser­va­tive” — pub­lished in the jour­nal Science Ad­vances.

“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.

The anal­y­sis 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 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.

For the study, re­searchers used a past ex­tinc­tion rate that was twice as high as widely used es­ti­mates.

If the past rate was two mam­mal ex­tinc­tions per 10,000 species per 100 years, then the “av­er­age rate of ver­te­brate species loss over the last cen­tury is up to 114 times higher than it would be with­out hu­man ac­tiv­ity, even when re­ly­ing on the most con­ser­va­tive es­ti­mates of species ex­tinc­tion,” said the study.

“We em­pha­size that our cal­cu­la­tions very likely un­der­es­ti­mate the sever­ity of the ex­tinc­tion cri­sis be­cause our aim was to place a re- al­is­tic lower bound on hu­man­ity’s im­pact on bio­di­ver­sity.”

The causes of species loss range from cli­mate change to pol­lu­tion to de­for­esta­tion and more.

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.

“There are ex­am­ples of species all over the world that are es­sen­tially the walk­ing dead,” Ehrlich said.

The study called for “rapid, greatly in­ten­si­fied ef­forts to con­serve al­ready threat­ened species, and to al­le­vi­ate pres­sures on their pop­u­la­tions — no­tably habi­tat loss, over-ex­ploita­tion for eco­nomic gain and cli­mate change.”

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