Pine Beetles Changing Rocky Mountain Air Quality, Weather

A new international field project, led by scientists at the National Center for Atmospheric Research in Boulder, is exploring how trees killed by the beetles influence rainfall, temperatures, smog and other aspects of the atmosphere.

"Forests help control the atmosphere, and there's a big difference between the impacts of a living forest and a dead forest," says NCAR scientist Alex Guenther, a principal investigator on the project. "With a dead forest, we may get different rainfall patterns, for example."

Pine bark beetles killed these lodgepole pines in the Rocky Mountains. (Photo courtesy U.S. Forest Service)

Beetle kill stimulates trees to release more particles and chemicals into the atmosphere as they try to fight off the insects, Guenther says. This worsens air quality, at least initially, by increasing levels of ground-level ozone and particulate matter.

The mountain pine beetle, Dendroctonus ponderosae, is a species of bark beetle native to the forests of western North America from Mexico to central British Columbia and Alberta.

Forests in Colorado, Wyoming, and South Dakota are experiencing bark beetle epidemics at a historically unprecedented scale, according to the U.S. Forest Service. A plan by the Service to deal with the beetles will log, burn, or spray 104,000 acres of lodgepole pines in the Rocky Mountain Region by 2011.

Researchers from the Canadian Forest Service have studied the relationship between the carbon cycle and forest fires, logging and tree deaths. They conclude that by 2020 the pine beetle outbreak will have released 270 megatonnes of carbon dioxide into the atmosphere from Canadian forests.

The NCAR project, known as BEACHON for Bio-hydro-atmosphere interactions of Energy, Aerosols, Carbon, H2O, Organics and Nitrogen, is funded by the National Science Foundation, NCAR's sponsor.

BEACHON will allow scientists to gain insights into cloud formation, climate change, and the cycling of gases and particles between the land and the atmosphere, according to Cliff Jacobs, program director in NSF's Division of Atmospheric Sciences.

The exchange of gases and particles between the surface and the atmosphere is critical in arid areas such as the western United States. Guenther says even slight changes in precipitation can impact the region.

The red on this map of Wyoming, Colorado and South Dakota shows areas of pine bark beetle infestation. (Map courtesy U.S. Forest Service)

"Here in the western United States, it is particularly important to understand these subtle impacts on precipitation," Guenther says. "Rain and snow may become even more scarce in the future as the climate changes, and the growing population wants ever more water."

Researchers will use aircraft as well as towers that reach above the forest canopy to measure emissions at 100 feet above the ground.

Additional data will come from soil and moisture sensors, instruments for gases and tiny particles, radars, and lidars, which are radar-like devices that use light instead of radio waves.

"BEACHON will give us a very comprehensive picture of a forest's impact on the atmosphere," Guenther says. "But at this point, we don't know what the project will reveal. We may end up with more questions than answers."

Organizations participating in the project include Colorado College, Colorado State University, Cornell University, Texas A&M University, and the universities of Colorado, Idaho, Minnesota, New Hampshire, and Washington, as well as the U.S. Forest Service, the U.S. Environmental Protection Agency, and universities in Austria, France and Japan.

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