New study shows U.S. forests under threat from climate change

U.S. forests are under threat from increasing drought and climate change, according to a new Duke University study.

While the consequences of climate change have mainly affected forests in the West—on top of drought-induced forest diebacks, bark beetle infestations and wildfires, they are now likely to become more severe, frequent and prolonged across much of the U.S.

“Our analysis shows virtually all U.S. forests are now experiencing change and are vulnerable to future declines,” said James S. Clark, lead author of the study and Nicholas Professor of Environmental Science at Duke University. “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.”

There is also mounting evidence that climate is changing faster than tree populations can respond by migrating to new regions. 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 favourable habitats through seed dispersal or other natural means.

The Impacts of Increasing Drought on Forest Dynamics, Structure, and Biodiversity in the United Statespublished in peer-reviewed journal Global Change Biology, synthesises findings from hundreds of studies and serves as a summary overview of a full report released earlier this month by the U.S. Department of Agriculture and the U.S. Global Change Research Program as part of the U.S. Forest Service’s National Assessment on the Impacts of Drought on Forests and Rangelands.

The new report also addresses management practices and critical knowledge gaps that hinder scientists’ ability to predict the pace and extent of future effects.

“Prolonged drought affects wildfire risks, species distribution, forest biodiversity and productivity, and forest-based products, so there is a pressing need to know how we can manage for these changes,” Clark said. “We currently have a pretty good handle on predicting the impacts of climate change and drought on individual trees. But there is still uncertainty about what might happen at the species-wide or stand-wide levels, particularly in Eastern forests.

“This is where we need reliable predictions so forest managers can take steps now to help reduce problems.”