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17 Sep 2012: Forest Mortality in U.S. Declines
As Beetles Run Out of Food, Report Says

Tree deaths caused by insect infestation and disease in the western U.S. declined significantly last year, largely because mountain pine beetles have devoured so many forests that they are running out of food,

What’s Killing the Great
Forests of the American West?

What’s Killing the Great Forests of the American West?
Across western North America, huge tracts of forest are dying off at an extraordinary rate, mostly because of outbreaks of insects. Scientists are now seeing such forest die-offs around the world and are linking them to changes in climate.
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according to a report by the U.S. Forest Service. Researchers reported that about 6.4 million acres of forest died nationally in 2011, compared with 9.2 million acres in 2010 and a peak mortality of 11.8 million acres in 2009. Scientists say about 60 percent of the mortality was caused by one pest, the mountain pine beetle, a native insect that has decimated lodgepole and ponderosa pine forests across western North America because warmer winters are not killing off beetle larvae. While the researchers say a critical factor in the decline has been a reduced number of available lodgepoles, they say ponderosa pine and high-elevation white bark pine remain at risk. The greatest forest mortality was reported in Colorado, Montana, Idaho, and Wyoming. In Montana alone, nearly 1 million acres have been affected. “Native insects and diseases run in cycles, and right now we are grateful the trend is downward,” said U.S. Forest Service Chief Tom Tidwell. He added, however, that forests still face significant threats, including from climate change and new invasive species.


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