New Tools for Urban Foresters

by Sarah Farmer, SRS Science Delivery Group

Mississippi State University students help collect data for the iTree analyses conducted in DeSoto County. Photo by Eric Kuehler.

Across the southeastern United States, rapid urbanization is transforming previously rural areas and creating new environmental challenges. Desoto County, Mississippi, is emblematic of these changes: since 1970, its population has increased by 430 percent, from 36,000 people in 1970 to 159,000 in 2010.

The Environmental Protection Agency lists Desoto County as an ozone non-attainment” area, which means ozone emissions are above allowable limits set by federal regulation. Ground level ozone, the main ingredient in smog, can trigger asthma attacks and causes lung damage. The ruling will likely mean that the state will have to take expensive actions to limit pollution emissions from cars and commercial/industrial sources.

Eric Kuehler is a U.S. Forest Service technology transfer specialist at Urban Forestry South, a research work unit of the Southern Research Station (SRS). Using data collected by local volunteers and forestry students from Mississippi State University, Kuehler and his colleagues conducted a series of analyses using iTree, a free, peer-reviewed software suite from the Forest Service that quantifies the environmental services trees provide.

In Desoto County, researchers assessed the structure, function, and value of the urban forest in terms of size and makeup of the urban canopy and its role in removing air pollution and sequestering carbon. The study aimed to establish a baseline for assessing tree cover in the county, and to describe the value of the urban forest in quantitative terms that would be useful for policymakers.

Kuehler and his colleagues found that over 19 million trees grew in Desoto County, with 27 percent of the county covered by tree canopy. In relation to the countys current air quality problems, the analysis estimated that trees in Desoto County currently remove 5,560 tons of air pollution (ozone, carbon monoxide, nitrogen dioxide, sulfur dioxide, and particulate) per year, at an estimated value of $40.5 million per year.

Landowners, residents and local officials in emerging urban areas like Desoto County can expect environmental challenges. However, counties can take significant steps to mitigate those problems by developing policies that restrict impervious surface cover development, reduce significant land changes from agriculture to urban—and increase tree canopy cover to help alleviate the heat island effect and ultimately reduce pollution levels.

“iTree describes the value of urban forests in terms that policymakers can understand. It provides good science-based information on the function and value of trees,” says Kuehler. “In this tough budgetary environment, counties are closely assessing how they allocate their scarce resources. If we can show the value that trees have in terms of pollution removal, reduction in stormwater runoff and erosion, and energy savings, local officials will look more closely at the value that urban forestry programs can contribute.” 

Excerpted from Josh McDaniels article in Leaves of Change, Issue 13, November 2012.

For more information, contact Eric Kuehler at ekuehler@fs.fed.us

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Posted in Economics & Policy, Ethics & Values, Urban Forests