Trouble in the Tropics

Thursday, September 4th, 2008--

When we think of global warming, polar bears or huge melting glaciers may come to mind. High latitude areas including the Arctic are undergoing the most extreme temperature changes and often have the most visible and dramatic consequences, according to a recent study in the journal Science.

But the research of biologist Joshua Tewksbury has shown that naturally warmer areas such as the tropics may be most threatened by climate change. Tropical organisms, says Tewksbury, assistant professor at the University of Washington, are habituated to slight temperature changes, if any at all. These organisms could find it difficult to adapt to quickly rising temperatures, he says.

“In order to be able to survive, you have to be able to handle changing temperatures, and these organisms have no predisposition for change,” Tewksbury says. Even though temperature in the tropics is expected to increase only two or three degrees within this century, while rising up to six degrees in the Arctic, organisms that are less used to temperature swings could be at greater risk of extinction. “The ability of organisms to respond to that change is really a function of variability in climate that they have experienced,” Tewksbury adds.

Christopher Raxworthy, associate curator of herpetology at the American Museum of Natural History in New York City, studies the effects of global warming on tropical organisms in the mountainous regions of Madagascar. His research suggests that tropical amphibians and reptiles adapt to rising temperatures by changing habitats and migrating up mountains.

As temperatures continue to climb however, animals are pushed to higher and higher altitudes, or further upslope. “If temperatures keep warming at the rates they are increasing right now, by the end of the twenty-first century those conditions they occupy now won’t even exist at the very top of the highest mountain in Madagascar,” says Raxworthy. He predicts that at least three species of amphibians and reptiles will go extinct in the next 50 years in Madagascar alone due to temperature change.

The government of Madagascar is attempting to mitigate the effects of global warming by setting aside land for the animals to migrate to, but its efforts are proving futile. No stretch of land within the island will allow species to fully escape the rising temps, according to Raxworthy. At some point, there simply won’t be a suitable habitat on the island for the affected animals.

Without a worldwide effort to reduce CO2 emissions, local efforts won’t be enough to save tropical species, the researchers fear. “We can’t discount local conservation efforts and at the same time, we have to look beyond them,” Tewksbury says.

--Liz Byrnes

Sources

Joshua Tewksbury
Assistant Professor, Biology
University of Washington
Seattle, Washington

Christopher Raxworthy
Associate Curator
Associate Dean of Science for Exhibition and Education
Department of Herpetology
American Museum of Natural History

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