AboutZoos, Since 2008


Nearly one-​tenth of hemisphere’s mam­mals unlikely to out­run cli­mate change

pub­lished 16 May 2012 | mod­i­fied 05 Decem­ber 2012

A safe haven could be out of reach for 9 per­cent of the West­ern Hemisphere’s mam­mals, and as much as 40 per­cent in cer­tain regions, because the ani­mals just won’t move swiftly enough to out­pace cli­mate change.

For the past decade sci­en­tists have out­lined new areas suit­able for mam­mals likely to be dis­placed as cli­mate change first makes their cur­rent habi­tat inhos­pitable, then unliv­able. For the first time a new study con­sid­ers whether mam­mals will actu­ally be able to move to those new areas before they are over­run by cli­mate change. Car­rie Schloss, Uni­ver­sity of Wash­ing­ton (UW) research ana­lyst in envi­ron­men­tal and for­est sci­ences, is lead author of the paper out online the week of May 14 in the Pro­ceed­ings of the National Acad­emy of Sci­ences.

We under­es­ti­mate the vul­ner­a­bil­ity of mam­mals to cli­mate change when we look at pro­jec­tions of areas with suit­able cli­mate but we don’t also include the abil­ity of mam­mals to move, or dis­perse, to the new areas
Car­rie Schloss, lead author of the study »

Indeed, more than half of the species sci­en­tists have in the past pro­jected could expand their ranges in the face of cli­mate change will, instead, see their ranges con­tract because the ani­mals won’t be able to expand into new areas fast enough, said co-​author Joshua Lawler, UW asso­ciate pro­fes­sor of envi­ron­men­tal and for­est sciences.

mammals dispersion

In par­tic­u­lar, many of the hemisphere’s species of pri­mates – includ­ing tamarins, spi­der mon­keys, mar­mosets and howler mon­keys, some of which are already con­sid­ered threat­ened or endan­gered – will be hard-​pressed to out­pace cli­mate change, as are the group of species that includes shrews and moles. Win­ners of the cli­mate change race are likely to come from car­ni­vores like coy­otes and wolves, the group that includes deer and cari­bou, and one that includes armadil­los and anteaters.

The analy­sis looked at 493 mam­mals in the West­ern Hemi­sphere rang­ing from a moose that weighs 1,800 pounds to a shrew that weighs less than a dime. Only cli­mate change was con­sid­ered and not other fac­tors that cause ani­mals to dis­perse, such as com­pe­ti­tion from other species.

To deter­mine how quickly species must move to new ranges to out­pace cli­mate change, UW researchers used pre­vi­ous work by Lawler that reveals areas with cli­mates needed by each species, along with how fast cli­mate change might occur based on 10 global cli­mate mod­els and a mid-​high green­house gas emis­sion sce­nario devel­oped by the U.N. Inter­gov­ern­men­tal Panel on Cli­mate Change.

The UW researchers cou­pled how swiftly a species is able to dis­perse across the land­scape with how often its mem­bers make such a move. In this case, the sci­en­tists assumed ani­mals dis­persed once a gen­er­a­tion. It’s under­stand­able, for exam­ple, that a mouse might not get too far because of its size. But if there are many gen­er­a­tions born each a year, then that mouse is on the move reg­u­larly com­pared to a mam­mal that stays sev­eral years with its par­ents in one place before being old enough to repro­duce and strike out for new territory.

West­ern Hemi­sphere pri­mates, for exam­ple, take sev­eral years before they are sex­u­ally mature. That con­tributes to their low-​dispersal rate and is one rea­son they look espe­cially vul­ner­a­ble to cli­mate change, Schloss said. Another rea­son is that the ter­ri­tory with suit­able cli­mate is expected to shrink and to reach the new areas ani­mals in the trop­ics must gen­er­ally go far­ther than in moun­tain­ous regions, where ani­mals can more quickly move to a dif­fer­ent ele­va­tion and a cli­mate that suits them. Those fac­tors mean that nearly all the hemisphere’s pri­mates will expe­ri­ence severe reduc­tions in their ranges, Schloss said, on aver­age about 75 per­cent. At the same time species with high dis­per­sal rates that face slower-​paced cli­mate change are expected to expand their ranges.

Our fig­ures are a fairly con­ser­v­a­tive – even opti­mistic – view of what could hap­pen because our approach assumes that ani­mals always go in the direc­tion needed to avoid cli­mate change and at the max­i­mum rate pos­si­ble for them

(Joshua Lawler, co-​author)

The researchers were also con­ser­v­a­tive, he said, in tak­ing into account human-​made obsta­cles such as cities and crop lands that ani­mals encounter. For the over­all analy­sis they used a pre­vi­ously devel­oped for­mula of “aver­age human influ­ence” that high­lights regions where ani­mals are likely to encounter intense human devel­op­ment. It doesn’t take into account tran­sit time if ani­mals must go com­pletely around human-​dominated land­scapes. “I think it’s impor­tant to point out that in the past when cli­mates have changed – between glacial and inter­glacial peri­ods when species ranges con­tracted and expanded – the land­scape wasn’t cov­ered with agri­cul­tural fields, four-​lane high­ways and park­ing lots, so species could move much more freely across the land­scape,” Lawler said.

Con­ser­va­tion plan­ners could help some species keep pace with cli­mate change by focus­ing on con­nec­tiv­ity – on link­ing together areas that could serve as path­ways to new ter­ri­to­ries, par­tic­u­larly where ani­mals will encounter human-​land development
“For species unable to keep pace, reduc­ing non-​climate-​related stres­sors could help make pop­u­la­tions more resilient, but ulti­mately reduc­ing emis­sions, and there­fore reduc­ing the pace of cli­mate change, may be the only cer­tain method to make sure species are able to keep pace with cli­mate change,” Schloss said.

The above news item is reprinted from mate­ri­als avail­able at the Uni­ver­sity of Wash­ing­ton. Orig­i­nal text may be edited for con­tent and length.

(Source: UWTo­day, 14.05.2012)

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