Climate Change Causes Megadisturbances in Temperate Forests

Temperate forests are vulnerable to worsening droughts, diseases, and massive wildfires, and the USDA Forest Service warns that if actions aren't taken, some forests could be transformed into shrublands or grasslands in the near future.

"While we have been trying to manage for resilience of 20th century conditions, we realize now that we must prepare for transformations and attempt to ease these conversions," Constance Millar, lead author and forest ecologist with the USDA Forest Service's Pacific Southwest Research Station, said.

Their study, recently published in the journal Science, explains that forests have been resilient in the wake of logging, and while they have been re-growing, they are being stressed by hotter, drier air temperature that overheat their leaves and steal all their moisture. It also doesn't help that snow, which would be stored for emergencies, is instead falling as rain. As a result, trees are experiencing a much higher mortality rate.

"Some temperate forests already appear to be showing chronic effects of warming temperatures, such as slow increases in tree deaths," Nathan Stephenson, coauthor and ecologist with the U.S. Geological Survey, said in a statement. "But the emergence of megadisturbances, forest diebacks beyond the range of what we've normally seen over the last century, could be a game-changer for how we plan for the future."

According to the release, trees are also being exposed to insect and disease outbreaks as temperatures increase. The researchers warn that if temperate forest loss is not managed, it could result in losses of forest ecosystem services, such as national park recreational areas. They also note the importance that forest play in storing atmospheric carbon dioxide and watershed protection.

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