New England forests at greater risk from air pollution

07/29/04

PORTLAND - When it comes to forests, air pollution is not an equal opportunity hazard.

While dirty air spreads across large areas of the New England region, it's more scattered in the southeastern part of the United States. Details were presented during a symposium on indicators of forest health on Tuesday, Aug. 3, at the annual meeting of the Ecological Society of America in Portland, Ore.

As part of national project to monitor the health of forests, including the trees and everything else living in these ecosystems, researchers from the University of Wisconsin-Madison and the U.S. Forest Service have turned to the leafy or tufted species of lichens.

Lichens typically live on tree trunks, branches and rocks on the forest floor, and they're well known for their sensitivity to environmental change, such as air pollution, says Susan Will-Wolf, a UW-Madison associate scientist in botany, who is involved in the project. "They're the 'canary in the mine' that can provide an advance warning of potential hazards."

Changes in lichen communities, she adds, are an indicator of the possibility for changes within the ecosystem, such as less-efficient nutrient cycling or slower forest growth. "While forests are important for timber production, they are also important for maintaining watersheds and protecting biodiversity," says Will-Wolf. "This ability may be impaired under certain conditions."

Recognizing the potential of these plants to signal changes in the environment, the Wisconsin botanist and her colleagues developed regional models based on lichen community composition to assign air-quality scores to forest plots and predict the impact of air pollution on forests. The models show, for example, that areas with dirtier air tend to have fewer species of lichens. The opposite is true for areas with cleaner air.

With these models, Will-Wolf and others used data collected by the U.S. Forest Service to monitor lichen communities and air pollution in New England and the Southeast. By tracking lichen community composition and related air-quality scores, the researchers created regional pictures indicating which forest areas are under the greatest threat from air pollution.

These pictures, notes Will-Wolf, look different between the two regions. Air pollution in the southern states, such as Georgia and Alabama, appears to concentrate in localized areas, whereas the dirtier air in the New England states, including Maine and New York, spreads across larger areas.

The results show, for instance, that while both geographical regions have air-quality scores indicating they are affected by air pollution, nearly one-eighth of the New England area is affected by air quality poorer than any area in the Southeast. Also, pollution sensitive lichens found in both regions are more restricted in their distribution in New England.

"The effects are scattered in the Southeast, with over a dozen small 20- to 50-mile wide pockets of lower air quality," says Will-Wolf. "In the New England region, the poorest air quality is concentrated in fewer, larger areas. One swath includes the East Coast from Boston to New York City, extending 50 to 100 miles inland." Another swath, she adds, covers the western half of New York.

These results, Will-Wolf explains, suggest that forests in New England, compared to those in the Southeast, are at greater risk from air pollution because the broader impact zones affect much of a particular habitat providing fewer refuges from dirty air.

Will-Wolf says this research, along with the national efforts of the forest-health monitoring program, is part of preventive measures to protect our forests and other natural areas from degradation due to environmental change.

"We know that it can take 30 years before cigarettes impact the body," she says. "It could take just as long for a moderate level of air pollution to show its effects on forests. We should do what we can to lower that chance before it's too late to reverse the effects."

She says that using lichen community composition as an indicator of air pollution not only will identify areas to target for management and prevention, but also provide a tool to track the effectiveness of recent regulations to reduce the amount of toxic chemicals released into the air.

Source: Eurekalert & others

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