The impact of global warming has become obvious in high latitude regions, including Alaska, Siberia and the Arctic, where melting ice and softening tundra are causing profound changes. But, contrary to popular belief, the most serious impact in the next century likely will be in the tropics, says a group of researchers headed by a University of Washington ecologist.

Scientists have noted warming at higher latitudes that already appears to be causing some flowers to bloom earlier than usual and seems to be altering some wildlife migration and hibernation patterns.

"You see this and you think the higher latitudes are really being hammered by climate change. We are arguing that this might not be true," said Joshua Tewksbury, a UW assistant professor of biology. "To predict the impact of climate change, we need to know the amount of change and how organisms are able to tolerate that change. Previous research has focused on change alone and ignored tolerance."

The more dramatic impact could actually be in the moist tropics, despite modeling that indicates temperatures there will warm just 2 or 3 degrees by 2100 compared with 6 degrees or more at higher latitudes, Tewksbury said. That is because organisms in the tropics normally do not experience much temperature variation because there is very little seasonality, so even small temperature shifts can have a much larger impact than similar shifts in regions with more seasonal climates.

"Temperatures in the tropics don't fluctuate that much, so the relatively small temperature shifts predicted by climate change models will be very large in relation to what organisms are adapted to tolerate," he said. "It's only going to be perhaps a 2-degree change, but in many tropical areas organisms have never experienced a 2-degree change."

By contrast, higher latitudes can have vast temperature fluctuations from hot summers to cold winters, and so plants and animals already are adapted to a
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Contact: Vince Stricherz
vinces@u.washington.edu
206-543-2580
University of Washington
12-Aug-2005

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