Fall colors fade in U.S. west as aspen trees die

By Laura Zuckerman

SALMON, Idaho (Reuters) - The American West is losing its autumn colors as global warming begins to bite and there is far more at stake than iconic scenery.

Aspen, the white-barked trees with golden leaves that gave their name to the famed Colorado ski resort, have been dying off across the Rocky Mountain states. The die-off is puzzling but some foresters point to climate change.

This disaster coincides with beetle outbreaks that have laid waste to millions of acres of pine and spruce forest in the American and Canadian west. They too have been linked to warmer winters since extremely cold temperatures are needed to kill the insects.

Recent droughts and other factors linked to global warming are seen as likely causes for "sudden aspen decline," or SAD, so named because it can strike a forest so quickly.

"Assuming climate predictions are true, it probably is a sign of things to come," said Jim Worrall, forest pathologist with the U.S. Forest Service.

Dwindling aspen would spell trouble for mountain towns like Aspen, Colorado, where tourists flock each autumn to see their spade-shaped leaves turn from green to gold before skiers arrive for the winter.

Failing aspen forests also hurt sawmills and threaten large animals such as elk seeking food with consequences for hunting and other outdoor industries.

The effects have yet to hit home in a city that trades on its scenic beauty, but officials are braced for the worst.

"A large die-off could be devastating," said Aspen Mayor Mick Ireland.

Colorado acreage ravaged by SAD quadrupled from 2006 to 2008 to more than 850 square miles (2,200 square km). The syndrome has also struck in Utah, Wyoming and Idaho, where researchers suggest a warmer, dryer West may all but eliminate aspen from the Rocky Mountains by the end of the century.

Stands afflicted by SAD lose leaves, are assaulted by insects and frequently fail to reproduce.

Delta Timber Co. in southwest Colorado, where SAD is at its height, depends almost entirely on aspen to produce paneling for walls and ceilings.

"We're struggling right now with the same thing all sawmills are facing because of the housing crunch," said owner Eric Sorenson. "Now with the trees dying, it's going to create more challenges."

NOTHING TO BE DONE?

Dale Bartos, aspen ecologist with the Rocky Mountain Research Station in Logan, Utah, is cautious about using climate-based forecasts to predict an end to aspen.