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"Drought inherently is not a bad thing," Plumb said on a recent visit to the snow-covered lake bed. "But with long-term drought you start to see these accumulating signals." Casual visitors to the park may have picked up on some of them. Parched streams and high temperatures last summer killed hundreds of fish and prompted park officials to temporarily close some waters to fishing. Pothole wetlands in some areas have vanished, stealing prime habitat for the park's struggling trumpeter swans.
There's less vegetation in the Gardiner basin for wildlife to munch on. Drought-weakened conifers have fallen victim to increasing numbers of tree-killing bark beetles. Drought also opens the door for non-native species to gain a foothold.
"Any time there's a shift, there are winners and losers in every ecological community," said Bob Garrott, a professor of ecology at Montana State University who has studied Yellowstone's ungulates for about 20 years.
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Precipitation levels in the latest drought roughly match dry periods back to the year 1173, he said. What's different now, though, is that summertime temperatures are, on average, warmer and winters are milder, allowing snowpack to melt weeks earlier than normal, said Steve Gray, who worked on the study when he was a U.S. Geological Survey scientist before he was hired as Wyoming's state climatologist. "That can really stress these natural systems," Gray said. But those are some of the kinds of changes that can be expected if predictions for a warming global climate play out in the West, he said. Yellowstone will probably see more subtle signs of climate change than Glacier National Park with its shrinking glaciers.
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http://www.billingsgazette.net/articles/2008/01/22/news/state/21-yellowstone.txt
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