Colorado aspen trees are ‘starving to death’ |

Colorado aspen trees are ‘starving to death’

Bob Berwyn
Summit County Correspondent
Vail, CO Colorado

SUMMIT COUNTY, Colorado ” Growing evidence shows drought conditions are killing Colorado’s aspens at an unprecedented rate.

More than 56,000 acres of aspens have recently died in the state, according to a paper published by a group of Forest Service scientists last year.

Nearly 10 percent of the aspen stands in the San Juan National Forest have been affected, with mortality increasing at a rapid rate.

An intense drought in the early 2000s likely triggered the startling decline in the health and vigor of one of Colorado’s signature trees, said James Worrall, one of the primary authors of the study.

“I didn’t feel comfortable making the direct link between climate change and aspen decline,” Worrall said. “But it’s safe to say, if the climate change predictions turn out to be true, we’re going to see more aspen problems.”

The tree’s range could shrink significantly, especially on south-facing slopes. On the other hand, it’s conceivable, but not likely, that aspens could spread to new areas in response to climate change, Worrall said.

Other instances of aspen mortality, for example in the Great Lakes region, have also been tied to warm and dry conditions, according to the report.

Drought and insects are believed to have caused the widespread death of aspens in the 1980s and 90s in the Canadian prairie provinces of Alberta and Saskatchewan.

And in the early 1970s, overgrazing by deer and elk, among other causes, is believed to have killed aspen trees in Utah and Wyoming.

But the rapid n decline in southern Colorado appears to be unprecedented. Aspen mortality in one part of the San Juan National Forest increased 58 percent from 2005 to 2006.

As the scientists studied aspen stands in four southern Colorado national forests, they also found that there is very little regrowth. The trees generally spread via suckers, or shoots of the roots of healthy trees. But after several years of drought, the trees don’t have the energy to regrow suckers, Worrall said.

“After years of drought, they’re basically starving to death,” Worrall said.

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