Nearly All US Forests Threatened by Drought, Climate Change

Forests nationwide are feeling the heat from increasing drought and climate change, according to a new study by scientists from 14 research institutions.

"Over the last two decades, warming temperatures and variable precipitation have increased the severity of forest droughts across much of the continental United States," said James S. Clark, lead author of the study and Nicholas Professor of Environmental Science at Duke University.

"While the effects have been most pronounced in the West, our analysis shows virtually all U.S. forests are now experiencing change and are vulnerable to future declines," he said.  "Given the high degree of uncertainty in our understanding of how forest species and stands adapt to rapid change, it's going to be difficult to anticipate the type of forests that will be here in 20 to 40 years."

Drought-induced forest diebacks, bark beetle infestations and wildfires are already occurring on large scales across the West, and many models predict droughts are likely to become more severe, frequent and prolonged across much of the United States.

There is also mounting evidence that climate is changing faster than tree populations can respond by migrating to new regions.  Clark said that as conditions become drier and warmer, many tree populations, especially those in Eastern forests, may not be able to expand rapidly enough into new, more favorable habitats through seed dispersal or other natural means.

Clark and his colleagues published their paper in the Early View online edition of the peer-reviewed journal Global Change Biology.

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