The effects of economic growth on interior forests of the Southeast

02/07/05

Defining conservation priorities using fragmentation forecasts

Recent USDA Forest Service research demonstrates how models can be used to forecast future forest conditions in areas of rapid development. In a report published this last fall in Ecology and Society, FS Southern Research Station (SRS) researchers David Wear, John Pye, and Kurt Riitters provide a visual forecast of the effects of population and economic growth on interior forest habitat in the Southeast over the next decades.

"Almost 90 percent of the land in the southeastern United State is privately owned," says Dave Wear, project leader of the SRS forest economics unit in Research Triangle Park, NC. "This means that major land use changes are being shaped by hundreds of thousands of individual decisions. We project that continuing urbanization and low-density residential development over the next decades, though focused in relatively small areas, could have a profound impact on the forest ecosystems in the Southeast."

A forest can be visualized as an island interior surrounded by an edge. Many species of animals, birds, reptiles, amphibians, insects, and plants that thrive in interior forest habitats cannot live in forest edge habitats. "Maintaining the species diversity of a forest means having suitable proportions of edge and interior habitats," says Kurt Riiters, deputy program manager for the SRS Forest Health Monitoring unit. "As development proceeds, edge habitat becomes more plentiful and interior habitat more scarce. For this study, we focused on interior forest as an indicator of available habitat for species that tend to decline when forests become too fragmented."

The researchers used county-level data to estimate and model changes in interior forest in a study area that included the 12 states in the southeastern United State bounded in the north by Kentucky and Virginia and in the west by Texas and Arkansas. At this time, most of these states are still more than 60 percent forested, but five of the states are among the top 10 nationwide for rates of urbanization.

The forecasts made in the article are the result of a sophisticated combination of economic analysis, land cover modeling, fragmentation analysis, and other factors. As expected, the researchers found that interior forest cover decreases in relation to increases in road density, population density, and household income. Interior forest also decreases as the value of agricultural products and site productivity rise. Forecasted changes, however, were not consistent across the region.

"Our forecasts to the year 2020 show the future loss of interior forest highest in the southern Appalachian piedmont of North and South Carolina, with the Gulf prairies and marshes in Texas and the Florida coastal lowlands following," says Wear. "We project that 66 percent of the loss of interior forests will come from urban counties, which indicates the importance of the forests that fringe major cities."

Seven of the 10 metropolitan areas slated to lose the most interior forests are in Florida, with the St. Petersburg-Clearwater area losing 34.5 percent of its interior forest. Columbia (South Carolina), Atlanta (Georgia), and the Research Triangle Area in North Carolina (Raleigh-Durham-Chapel Hill) round out the top 10. Large areas of interior forest loss are also forecast for counties around Knoxville and Nashville in Tennessee, and counties along the Gulf of Mexico from the panhandle of Florida to Louisiana.

"With the exception of the southern Appalachian highlands, where a quarter of the land is publicly owned, the future protection of biodiversity in the Southeast will depend on what happens on private land," says Wear. "The model presented in our article gives us the ability to focus our attention on the areas where biodiversity is most threatened by development and population growth."

Source: Eurekalert & others

Last reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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