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Do pine beetles pollute the air?

September 24, 2008 |  4:15 pm

Pine beetle

Dead and dying forests across about 50 million acres from Alaska and Canada to the Southwestern United States attest to the devastation wrought by a massive infestation of pine beetles over the past decade. Scientists have documented that the withered, dry trees cough out millions of tons of carbon dioxide into the atmosphere, trapping heat and contributing to the greenhouse effect that is warming the earth's climate.

Now, an international team led by scientists from the National Center for Atmospheric Research (NCAR), a federally-funded laboratory, is exploring new dangers: the tiny insects, each the size of a grain of rice, may also be altering rainfall patterns and polluting the air we breathe.

Large areas of dead trees may change cloud and precipitation patterns for a decade or more, scientists have found. "In the Western United States, it is particularly important to understand these subtle impacts on precipitation," said NCAR scientist Alex Guenther, a principal researcher on the project. "Rain and snow may become even more scarce in the future as the climate changes, and the growing population wants ever more water."

Preliminary computer modeling suggests that temperatures may increase temporarily as much as 2 to 4 degrees Fahrenheit, as a result of the beetle infestation. The lack of foliage diminishes the reflection of the sun's heat back into space. And, according to the scientists, beetle attacks may stimulate trees to release more particles and chemicals into the atmosphere as they try to fight off the insects. That increases ground level ozone and particulates, which can cause respiratory disease in humans.

The four-year field project, known as BEACHON, was launched this summer and is funded by the National Science Foundation. It includes scientists from nine U.S. colleges and universities, federal agencies and universities in Austria, France and Japan.

-- Margot Roosevelt

Photo: Mountain Pine Beetle; Credit/USDA Forest Service