May 25, 2012
Beetles Contribute To Air Pollution In Forests
Brett Smith for RedOrbit.com
Activity of the bark beetle is having an impact on both air quality and climate, according to a new report from a team of American scientists published in the journal Environmental Science & Technology.
Evidence of the beetle´s impact can be seen in the lodgepole pine forests of the western United States. Many of the trees there are dying or ravaged by the beetles and a faint haze of particulate matter can be seen throughout the area.
Air samples collected near beetle-infested and non-infested lodgepole pines, showed a large increase in atmospheric gases, particularly volatile organic compounds (VOC) given off by beetle activity, which could enhance airborne particulate matter problems and haze in the area.
"I look at how new particulate matter is formed and what its sources are,” said Southern Illinois University assistant professor and study co-author Kara Huff Hartz.
"To me, this study looked at a potential source of particulate matter we didn't think of before," she told an SIU newspaper.
"So if we can characterize it, maybe we can contribute to a better understanding of how much particulate matter is being formed in the atmosphere."
Airborne particulate matter is made up of fine particles suspended in the atmosphere where they can be inhaled. The source of particulate matter could be natural or manmade, but it is typically considered to be hazardous. Depending on the type or particulate, its concentration, and its location-- particulate matter can also impact climate by causing haze, preventing rain or leading to cooling, according to Huff Hartz.
Chemicals or gases in the air can also affect the impact of particulate matter. VOCs, like those created by the beetle activity, can interact with human-created oxidants caused by the burning of fossil fuels to enhance or create particulate matter.
"If it was just the biogenic VOCs and along with very little oxidants we wouldn't have this issue. It's the enhancement that happens that we're concerned about," Huff Hartz said. "They form a product that is less volatile than it was before, and it can condense onto existing particulate matter, making it larger, or can even make more of it."
Huff Hartz added that the researcher team isn´t sure why infested trees give off increased levels of VOCs. She theorized that it could be the beetle opening the tree trunk at a spot where it normally would be closed and allowing the naturally produced VOCs to escape. She also speculated that increased levels of VOCs are caused by a reaction between the tree and symbiotic fungi that the beetles carry with them on their bodies.
In addition to eating the protective bark of trees, some species of beetle carry fungi on them that can decimate a tree population. The American elm bark beetle has been known to carry the fungus responsible for Dutch Elm disease.
Scientists believe that the warmer weather associated with climate change has increased the bark beetle's range in recent years. According to Huff Hartz, researchers have a lot of work ahead in figuring out the relationships among the beetles, VOC emissions, particulate matter and climate change.
"If climate change is anthropogenic driven, is this really natural? It's an intriguing question," she said.