Problem facing species displaced by warming: nowhere to run

In a fragmented landscape – and with such rapid change – scientists worry that many plants and animals won't make it to cooler regions.

from the June 21, 2007 edition

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Some 25 percent of all known species – plant and animal – could succumb to these combined stresses by century's end, according to the IPCC. So many species disappearing so quickly hasn't happened since an asteroid slammed into Earth 65 million years ago.

With mass extinctions in the making, scientists are scrambling for ways to lessen global warming's impact. They suggest giving wildlife space to adjust with "biological corridors," highways of nature that connect wilderness areas up mountains and across latitudes. They propose intentionally moving those species that may not be able to adjust fast enough. And they advocate captive breeding – or banking – of those species in immediate danger of disappearing.

The motives behind these efforts are not just altruistic. Losing any species could mean losing proteins and enzymes found nowhere else – substances of potential value to pharmaceutical companies. But in a broader sense, humans rely on functioning ecosystems for what scientists call "ecosystem services": Fresh water comes from forest-covered mountaintops, fish from healthy seas. Losing wildlife means pushing these systems closer to collapse.

"Ultimately you'll have ecosystems that just disassemble," says Thomas Lovejoy, president of the Heinz Center for Science, Economics, and the Environment in Washington, D.C. "And we've never lived in a world like that."

Many species have survived huge changes in Earth's climate over millions of years, leading some people to ask why species won't be able to simply adapt again.

But this time the warming is different, says Jack Williams, an assistant professor of geography at the University of Wisconsin at Madison.

All of human history has taken place during an "interglacial," a relatively warm period in Earth's climate cycle. Humans think that current conditions are the norm. But in fact, ice age conditions have persisted during 80 percent of the time since the most recent ice age cycle began 1.8 million years ago; only 10 to 20 percent of that time has been "normal," Dr. Williams says.

Because Earth is already in a warm period, still higher temperatures may push some wildlife off the map. "You can't just pick them up and plop them somewhere else," Williams says. "These climate zones will actually disappear from the entire globe by the end of the century."

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