‘Sixth ex­tinc­tion’ of wildlife faster than feared

Kuwait Times - - HEALTH & SCIENCE -

The sixth mass ex­tinc­tion of life on Earth is un­fold­ing more quickly than feared, sci­en­tists have warned. More than 30 per­cent of an­i­mals with a back­bone - fish, birds, am­phib­ians, rep­tiles and mam­mals - are de­clin­ing in both range and pop­u­la­tion, ac­cord­ing to the first com­pre­hen­sive anal­y­sis of these trends. “This is the case of a bi­o­log­i­cal an­ni­hi­la­tion oc­cur­ring glob­ally,” said Stan­ford pro­fes­sor Rodolfo Dirzo, co-au­thor of a study pub­lished on Mon­day in the peer-re­viewed US jour­nal, Pro­ceed­ings of the Na­tional Acad­emy of Sciences (PNAS).

Around a decade ago, ex­perts feared that a new plan­e­tary wipe­out of species was loom­ing. To­day, most agree that it is un­der­way - but the new study sug­gests that the die-out is al­ready ratch­et­ing up a gear. It pro­vides much-needed data about the threat to wildlife, map­ping the dwin­dling ranges and pop­u­la­tions of 27,600 species. For 177 mam­mals, re­searchers combed through data cov­er­ing the pe­riod 1900 to 2015. The mam­mal species that were mon­i­tored have lost at least a third of their orig­i­nal habi­tat, the re­searchers found. Forty per­cent of them - in­clud­ing rhi­nos, orang­utans, go­ril­las and many big cats - are sur­viv­ing on 20 per­cent or less of the land they once roamed. The loss of bio­di­ver­sity has re­cently ac­cel­er­ated. “Sev­eral species of mam­mals that were rel­a­tively safe one or two decades ago are now en­dan­gered,” in­clud­ing chee­tahs, lions and gi­raffes, the study showed.

Glob­ally, the mass die-off - deemed to be the sixth in the last half-bil­lion years - is the worst since three-quar­ters of life on Earth, in­clud­ing the non-avian di­nosaurs, were wiped out 66 mil­lion years ago by a gi­ant me­teor im­pact. On av­er­age, two ver­te­brate species dis­ap­pear ev­ery year. Trop­i­cal re­gions have seen the high­est num­ber of de­clin­ing species. In South and South­east Asia, large-bod­ied species of mam­mals have lost more than four-fifths of their his­tor­i­cal ranges.

Habi­tat loss

While fewer species are dis­ap­pear­ing in tem­per­ate zones, the per­cent­age is just as high or higher. As many as half of the num­ber of an­i­mals that once shared our planet are no longer here, a loss the au­thors de­scribed as “a mas­sive ero­sion of the great­est bi­o­log­i­cal di­ver­sity in the his­tory of Earth”. There is no mystery as to why: Our own ever-ex­pand­ing species - which has more than dou­bled in num­ber since 1960 to 7.4 bil­lion - is eat­ing, crowd­ing and pol­lut­ing its plan­e­tary co-habi­tants out of ex­is­tence.

By com­par­i­son, there are as few as 20,000 lions left in the wild, less than 7,000 chee­tahs, 500 to 1,000 gi­ant pan­das, and about 250 Su­ma­tran rhi­noc­eros. The main driv­ers of wildlife de­cline are habi­tat loss, over­con­sump­tion, pol­lu­tion, in­va­sive species, dis­ease, as well as poach­ing in the case of tigers, ele­phants, rhi­nos and other large an­i­mals prized for their body parts. Cli­mate change is poised to be­come a ma­jor threat in the com­ing decades, with some an­i­mals - most fa­mously po­lar bears - al­ready in de­cline due to ris­ing tem­per­a­tures and chang­ing weather pat­terns.

“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,” said lead au­thor Ger­ardo Ce­bal­los of the Na­tional Au­tonomous Univer­sity of Mex­ico. Be­yond any moral im­per­a­tive, there are prac­ti­cal rea­sons to rue the eclipse of an­i­mals, whether megafauna or smaller and less “charis­matic” crea­tures, the re­searchers cau­tioned.

The vanishing of a top-level car­ni­vore or her­bi­vore can have a cas­cad­ing ef­fect down the food chain, dis­rupt­ing en­tire ecosys­tems. Other species di­rectly pro­vide “ser­vices” to hu­mans, such as hon­ey­bees that pol­li­nate crops or birds that en­sure pest con­trol. Pre­vi­ous stud­ies show that ecosys­tems un­der stress, while re­silient, have a break­ing point rapid change can lead to col­lapse. —AFP

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