Cities can improve their air quality, and make themselves more breathable for inhabitants, if they plant the right mix of trees for their climate, according to the results of a study announced Saturday (Oct. 7, 2006) by the College of Environmental Science and Forestry at the State University of New York in Syracuse.

Car exhausts, industrial smokestacks, and other fuel-driven trappings of urban life spew carbon -- believed by many researchers to be tied to global warming -- into the atmosphere. All trees remove carbon, but some are better at it then others. Unfortunately, the best carbon-scrubbing trees also emit volatile organic compounds (VOCs) that create respiratory ailments in humans, and cause some rubber and plastics to deteriorate.

Blending a city's greenery, the study shows, can remove carbon from the atmosphere while also reducing smog-causing VOCs. An ideal combination ultimately would result in maximum breathability benefits. “If the urban forest mixture is changed to include more desirable trees, and the locations of certain trees are chosen carefully," the study reports, any city can help lower the amount of pollutants in its air.

Landscaping and curb appeal are always items of interest to home sellers and buyers. However, increasing public awareness of environmental fragility has caused buyers to "think green" in selecting everything from homes built with energy-saving features to neighborhoods with parks, walking trails and open space. “Trail networks have become a selling point for municipal governments and developers marketing to people seeking activity-friendly communities,” agrees Dr. John Librett, a University of Utah professor who has conducted national surveys to learn who uses community trails.

"Trees serve other functions too," acknowledges Dr. Richard C. Smardon, chair of the college's Faculty of Environmental Studies. "They are aesthetic, they help control runoff, and they affect the microclimate,” he notes.

To determine the best mix of trees for any urban area, study researchers say they would rely on the U.S. Forest Service's Urban Forest Effects Model (UFORE), which helps quantify urban forests and the functions they perform. The model uses field, air pollution and meteorological information to calculate attributes about a particular city's forest. Not all cities have UFORE data available yet.

In every area, researchers add, they would follow Forest Service management recommendations by planting native or non-invasive trees with specific qualities: large size (at least 25 feet tall), long life (50 years plus), and disease resistance.