Sci­en­tists: Mass ex­tinc­tion looms

But oth­ers claim tone of re­port is too alarmist

The Denver Post - - NEWS - By Kris­tine Phillips


Have hu­mans dam­aged the Earth’s ecosys­tems so se­verely that we’re well on our way to the big­gest mass ex­tinc­tion since the di­nosaurs van­ished 66 mil­lion years ago? And are we run­ning out of time to re­verse the neg­a­tive im­pacts of our ac­tions?

Three sci­en­tists who have stud­ied ex­tinc­tions of thou­sands of species of ver­te­brates be­lieve so, al­though oth­ers are skep­ti­cal of the dooms­day-like find­ings.

A study pub­lished this month paints a grim pic­ture: The pop­u­la­tions of nearly 9,000 ver­te­brate species, in­clud­ing mam­mals such as chee­tahs, lions and gi­raffes, have sig­nif­i­cantly de­clined be­tween 1900 and 2015. Al­most 200 species have gone ex­tinct in the past 100 years. The study says the losses are in­dica­tive of the planet’s “on­go­ing six ma­jor ex­tinc­tion events” and has cas­cad­ing con­se­quences for hu­man life on Earth.

“This is the case of a bi­o­log­i­cal an­ni­hi­la­tion oc­cur­ring glob­ally, even if the species these pop­u­la­tions be­long to are still present some­where on Earth,” Rodolfo Dirzo, the study’s co-author and a Stan­ford Univer­sity bi­ol­ogy pro­fes­sor, said in a news re­lease.

The re­searchers an­a­lyzed 27,600 species of birds, am­phib­ians, mam­mals and rep­tiles — about half of all known ver­te­brate species — and found that 8,851 (about 32 per­cent) have seen de­clin­ing pop­u­la­tions and shrink­ing ar­eas of habi­tat. A more de­tailed anal­y­sis of 177 mam­mal species found that more than 40 per­cent have ex­pe­ri­enced sig­nif­i­cant drops in pop­u­la­tion. The find­ings, the study says, mean that bil­lions of an­i­mal pop­u­la­tions that once roamed the Earth are now gone.

The au­thors de­scribe the shrink­ing pop­u­la­tion of species as “a mas­sive ero­sion of the great­est bi­o­log­i­cal di­ver­sity in the his­tory of Earth.”

“Thus, we em­pha­size that the sixth mass ex­tinc­tion is al­ready here and the win­dow for ef­fec­tive ac­tion is very short, prob­a­bly two or three decades at most,” the au­thors wrote. “All signs point to ever more pow­er­ful as­saults on bio­di­ver­sity in the next two decades, paint­ing a dis­mal pic­ture of the fu­ture of life, in­clud­ing hu­man life.”

A few ex­am­ples: There were only a lit­tle more than 7,000 chee­tahs in ex­is­tence last year, and their pop­u­la­tion may drop an­other 53 per­cent in the next 15 years, ac­cord­ing to Na­tional Ge­o­graphic. Bor­neo and Su­ma­tran orang­utans have been con­sid­ered en­dan­gered for years mainly be­cause of loss of habi­tat.

The pop­u­la­tion of African lions has dropped by more than 40 per­cent in the past 20 years. West African lions, in par­tic­u­lar, are near­ing ex­tinc­tion, with only about 400 an­i­mals left. His­tor­i­cally, lions roamed south­ern Europe, the Mid­dle East, north­west­ern In­dia and most of Africa. To­day, there are only scat­tered pop­u­la­tions in sub-Sa­ha­ran Africa and a few rem­nants at Gir For­est Na­tional Park in In­dia, ac­cord­ing to the study.

The driv­ing force is a steady drum­beat of hu­man ac­tiv­i­ties that re­sult in habi­tat losses, pol­lu­tion and cli­mate dis­rup­tion, among oth­ers.

“The mas­sive loss of pop­u­la­tions and species re­flects our lack of em­pa­thy to all the wild species that have been our com­pan­ions since our ori­gins,” the study’s lead author, Gerardo Ce­bal­los, an ecol­ogy pro­fes­sor at the Univer­si­dad Na­cional Autónoma de Méx­ico, said in the news re­lease.

Some in the sci­en­tific com­mu­nity dis­agree with the study’s grim find­ings. Stu­art Pimm, head of the con­ser­va­tion ecol­ogy at Duke Univer­sity, said the study un­nec­es­sar­ily raises alarms. Pimm be­lieves the sixth mass ex­tinc­tion is just be­gin­ning, not well on its way.

“It’s a lit­tle bit dra­matic,” Pimm said. “Yes, we are driv­ing species to ex­tinc­tion a thou­sand times faster than we should. So yes, there is a prob­lem. But on the other hand, telling peo­ple that we’re all doomed and go­ing to die isn’t ter­ri­bly help­ful.”

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