"Unprecedented" Insect Infestations Devastating Western Forests - NYT

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PLAINS, Mont. - "A pair of dead brown pine trees stand like skeletons in the Lolo National Forest here, victims of a tiny, voracious insect called the mountain pine beetle. And although the nearby trees look healthy, their days are numbered, too; beneath them, little piles of brown boring dust testify that beetles are inside them, munching away.

It is a growing problem around the West. Unusually warm temperatures have extended the life and range of this and other bark beetles over the last several years. Trees have been weakened by several years of severe drought. Decades of zero tolerance for forest fires (a policy that is changing) left many forests far too dense with trees, a fertile environment for hungry beetles. All of it has led to an explosion of insect-killed trees in conifer forests.

From Alaska to Arizona and South Dakota to California, several kinds of bark beetles are killing large swaths of ponderosa, piñon and lodgepole pines and other trees. Much of the kill is taking place in publicly owned forests, but many private landowners who built homes in the forest are also watching as the trees around them die. "The outbreak we're seeing in Arizona and New Mexico is unprecedented," said Dr. Karen Clancy, a research entomologist with the United States Forest Service in Flagstaff, Ariz., who is studying bark beetle damage to the ponderosa and piñon pines. "In some piñon pine forests the mortality rate is 100 percent." Over all, 2 to 3 percent of the forest is affected in those states.

Some experts worry that the widespread damage may be part of a vast ecological shift in response to warming temperatures. "As the climate is changing, these ecosystems are rearranging themselves," said Dr. Craig Allen, a research ecologist with the United States Geological Survey in New Mexico. "Massive forest die-back is one way these systems will reassemble." In a similar drought in the 1950's, two-thirds of the trees were killed and seedlings grew to take their place. But with mortality near 100 percent, there are no new piñons coming up; they may be leaving the ecosystem. "This is an indication of big, fast changes in forests that's predicted by climate change models," Dr. Allen said."

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http://www.nytimes.com/2004/07/13/science/13beet.html