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Study Finds Drought, Heat Kill Subalpine Trees In Colorado

The team studied trees on Niwot Ridge near Boulder.
Courtesy Robbie Andrus
The team studied trees on Niwot Ridge near Boulder.

A study from the University of Colorado Boulder has found that trees in the state are dying from drought and heat.

Scientists monitored 5,000 trees in subalpine forests without wildfires or pest infestations, like bark beetles.

A certain amount of tree death is normal, but Robbie Andrus, a postdoctoral researcher at Washington State University and previous graduate student at CU Boulder, said deaths have tripled since the 1980s.

Higher death rates occurred during warmer and drier summers.

“In many of our stands we found that the rates of mortality of the oldest and largest trees are increasing more rapidly than the smaller and younger trees,” he said. “This is really important because the largest trees are the ones that store the most carbon.”

Climate change has also made it more difficult for young seedlings to grow.

“If we have an increase in tree mortality and a decrease in the number of new seedlings, then overall the population of subalpine trees is going to decrease,” said Andrus.

Subalpine forests are an important wildlife habitat, covering over 10,000 square miles of Colorado. Andrus said if global warming continues, tree deaths will keep increasing.

I am the 2021 American Association for the Advancement of Science Mass Media Fellow at KUNC. My goal is to tell the true stories of science — and make them understandable and fascinating for all.
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