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The Arctic isn’t alone

Small temperature changes near the equator could have a big impact on some animals

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4:07pm, May 5, 2008
Magazine issue: Vol. 173 #17, May 24, 2008
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Insects, turtles and other creatures that regulate their body temperature externally may find themselves in hot water as global temperatures increase, a new study finds.

In the tropics, many of these animals are already living at the temperatures their bodies like best and therefore they have less wiggle room for dealing with a warming world than animals living elsewhere.

Even though temperatures in the tropics are predicted to increase less than in higher latitude regions, certain animals living in these already warm places may be especially vulnerable, the study suggests. It isn’t just the rate of warming that will matter, but also the basic physiology of the animals in those climates, says Curtis Deutsch of the University of Washington in Seattle. Insects and “cold-blooded” animals such as lizards or frogs depend on their environment for temperature regulation. Turtles don’t just bask in the sun for pleasure — it is a means to warm up. How these animals will fare as temperatures change is unclear.

To investigate, Deutsch and his colleagues at the University of Washington and ColoradoStateUniversity in Fort Collins, Colo., gathered existing data for 38 species of insects and for some frogs, toads, lizards and turtles. The researchers then integrated animal physiology data with climate models from the Geophysical Fluid Dynamics Laboratory at PrincetonUniversity. Those models simulate global temperatures for the years 2070 to 2100. Results of the new analysis, published in the May 6 Proceedings of the National Academy of Sciences, suggest that animals in polar regions aren’t the only ones worth worrying about as global temperatures rise. Even though temperature changes in the tropics won’t be as drastic as near the poles, small changes may push some animals over the edge. At higher latitudes however, the inverse may be true. Since northern temperatures are currently less than ideal for many insects, they may thrive when warmer weather arrives, the researchers report.

“There will be some winners and losers — it’s hard to predict who those are,” says Deutsch, now at UCLA. “But the reorganization of elements of an ecosystem is probably going to be more destructive to biodiversity than constructive.”

Lisa Crozier of National Oceanic and Atmospheric Administration’s NorthwestFisheriesScienceCenter in Seattle, who has investigated the effects of climate change on various animals, says the study draws attention to an area in need of more work. “This is a very different way of thinking about the climate question,” she says.

Of course, there are many factors that will determine the winners and losers, says Deutsch. Insects, which have a much shorter generation time than turtles, for example, may be able to adapt more quickly to changing temperatures. And creatures that can move — either up a mountain or away from the equator — may find their way to hospitable environments. But whether the organisms that they are linked to — a butterfly’s food plant, for example — will move as well is unclear, making the structure of future ecosystems very hard to predict.

“Ecosystems are a very complicated fabric of interactions between species,” Deutsch says. “When you tug on that fabric and break some of the linkages, the predictive power collapses.”

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