Warming's biggest wallop aimed at wildlife, not people

Some of Earth's coldest areas will lose the climate zones that support today's plants and animals, says a UN panel's latest report.

from the April 6, 2007 edition

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In general, "With the small climate change we've already had, 59 percent of the world's species have shown a response – on all continents, in all major oceans, and across taxonomic groups," says Dr. Parmesan. Some 70 species have become extinct, largely at the poles or on mountaintops, where cold-adapted organisms have no place left to go as warmth creeps into higher latitudes and altitudes. Others, such as polar bears, are threatened. In other cases, rising CO2 levels are forcing organisms into a new regime where they have to compete for resources. In California, for example, researchers have found that higher CO2 levels have delayed flowering in some wild grasses but accelerated it in wild herbs that share the same turf. This is forcing the plants to compete directly for nutrients – ultimately changing the character of the ecosystem.

In the oceans, researchers are noting shifts in fish migration patterns. Coral-reef bleaching remains a concern, but its connection to global warming is still somewhat contentious, notes Chris Langdon, a marine scientist at the University of Miami's Rosenstiel School of Marine and Atmospheric Science. Measurements don't go back far enough in time to see if bleaching events are any more frequent than in the past.

But ocean acidification, a byproduct of rising CO2 levels in the air, is far more straightforward. It threatens a range of organisms – from tiny shell-forming plankton to reefs themselves. Some researchers say the changes in ocean chemistry from human CO2 emissions are expected to last from tens of thousands to hundreds of thousands of years, until natural buffering can take hold.

With some care and feeding, however, some ecosystems may be able to retain their resilience in the face of changes expected from global warming. Researchers at Duke University have found, for example, that if rates of sea-level rise remain relatively low, tidal marshes build themselves to keep pace, continuing to provide a buffer against storm surge and serving as a nursery for marine life.

"Marshes are not necessarily doomed," says Matt Kirwan, who led the study.

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