OCTOBER 14, 2009
Aspen Trees Die Across the West
Mysterious Ailment, in Wake of Pine-Beetle Invasion, Diminishes Fall Foliage
By STEPHANIE SIMON
WSJ
DENVER -- This should be the golden season across the West, when aspen paint hillsides in shades of fall. But a mysterious ailment -- or perhaps a combination of factors -- is killing hundreds of thousands of acres of the trees from Nevada, New Mexico and Arizona through Utah, Colorado, Wyoming and into Canada, according to the U.S. government and independent scientists. The aspen die-off comes on the heels of a pine-beetle invasion that has destroyed millions of acres of evergreens. Foresters expect to lose virtually every mature lodgepole pine in Colorado -- five million acres of them.
Aspen and lodgepole pine intermingle across many Rocky Mountain slopes at elevations of 5,000 to 8,000 feet. Millions of the trees are now down or brown, transforming the landscape into a huge fire risk. To the dismay of hunters, the dying trees are decimating habitat crucial to elk, as well as to such smaller animals as wolverine, lynx and yellow-bellied marmot. State and local officials fear a drop-off in fall-foliage tourism, and residents complain about diminished views. "It makes a big brown hole in the fall colors. A whole lot of brown holes," said Rod Sweet, who lives in Durango, Colo.
Researchers believe they understand why the beetles have been thriving. Temperatures in the mountains have been unusually warm over the past several winters, and it takes a long, hard freeze to kill beetle larvae. Also, decades of logging restrictions and a policy of fighting most fires rather than letting them burn have left the forests full of the century-old lodgepole pines that are the beetles' favorite nosh. In 2002, the U.S. Forest Service began investigating reports that entire stands of aspen were dying in the San Juan Mountains in southwest Colorado, and in an odd way. Usually when mature aspen fail, they send out hundreds of new shoots, called suckers, through their root systems. Those shoots sprout quickly, and the grove regenerates. But in the San Juans, the shoots were dying, too, or were failing to sprout. That phenomenon was named Sudden Aspen Decline, or SAD, but scientists say they don't fully understand it.
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Years of drought in Colorado, Utah and elsewhere appear to have severely stressed some aspen, leaving them susceptible to systemic disease, said Dale Bartos, an aspen ecologist with the U.S. Forest Service. In northern Arizona, wildlife may be the culprit: With the wolf population down, elk aren't often on the run from predators, giving them plenty of time to hunker in an aspen grove and methodically eat every sucker. Fire suppression, which has been emphasized as more homes are built in forested areas, may play a role, because fires typically spur regeneration. Another theory is the tree die-off is part of a normal progression -- albeit on an unusually broad scale -- of aspen giving way to conifer forests or alpine grassland.
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http://online.wsj.com/article/SB125547187504583409.html (subscription)
Printed in The Wall Street Journal, page A3
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