Trees are always shifting in response to their environment. But the pace Fei and his colleagues clocked over the past 30 years is far more rapid than has been seen in historical records. It’s comparable to speeds estimated to have occurred as the glaciers retreated at the end of the last ice age, he said.
Climate change isn’t the only factor in that process – American woodlands are also under pressure from pests and development, Fei noted, and new plantings from conservation programs also affect their ranges. But climate change accounts for about 20 percent of the changes.
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Fei and his colleagues compiled their results from reams of US Forest Service records — an annual count from more than 100,000 locations around the country.
“These are boots on the ground,” he said. “This is something I think is really unique about this study. This is empirical data — people on the ground, counting the trees, not modeling or estimating how many trees we have or how many we’ll have in the future.”
“I think one very important thing from our study was that we’d better pay close attention to precipitation patterns and moisture change,” Fei added. “Changing moisture variability has a much stronger near-term impact on the ecosystem that we’re looking at than temperature.”
Climate scientists have a good track record of modeling future temperatures, and the warming now under way is expected to produce more extreme weather events — but according to Fei, models of future precipitation trends are far less developed.
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