A Pixel Worth 1,000 Words
Satellite images reveal startling tree loss in American cities
Counting trees. Impressed with the system's capabilities, planners in the prosperous suburb of Bellevue, just across Lake Washington from Seattle, decided to conduct a more detailed study of the their own town's tree cover, neighborhood by neighborhood. To do this, they bought a scaled-down version of the American Forests mapping software, called CITYgreen. The $800 package is designed to help cities manage existing trees and minimize future environmental damage by calculating the effects of proposed development.
Aerial photos of Bellevue were taken with a digital mapping camera. From the data, planners outlined representative plots of different types of tree cover. A local leadership group and student volunteers then went out on foot to assess the size, health and species of all trees on the sample plots.
Bellevue just completed its local analysis this spring, but planners already credit the project with at least two tree-preservation victories--stopping one effort by property owners to cut down trees to enlarge their view, and adding more land to Bellevue's park system. "It's a marketing tool to get the information out in an easily digestible manner," says Dan DeWald, Bellevue's natural resources manager. After being shown the dollar benefits of open space, DeWald says, policy makers "didn't blink an eye at the cost" of the land.
Smart growth. The Pacific Northwest is not alone in finding that a booming economy and robust development mean fewer trees. American Forests has found significant tree loss from the early 1970s to the mid-1990s in every area it has surveyed. Metropolitan Atlanta, once famed for its trees, lost more than half of its heavy tree cover (50 percent canopy coverage) between 1974 and 1998, a drop from 57 percent to 30 percent. Heavy tree cover in the Canton-Akron area of Ohio shrank from 55 percent to 38 percent; in Roanoke, Va., it decreased from 40 to 35 percent.
In Atlanta, sprawl-induced air quality problems have grown so severe that last year the federal government banned new highway construction until the area can come up with a better plan to manage growth. "Trees are bulldozed every day, and I get calls every day from people asking 'what can I do?' " says Marcia Bansley, director of the nonprofit group Trees Atlanta. "People are very, very upset. If you're going to have smart growth, you're going to have to have some way to preserve green spaces so people don't feel like they're living in a desert."
Last month, Georgia Gov. Roy Barnes appointed Joel Cowan, an environmentalist and developer, to lead the Georgia Regional Transportation Authority, a commission formed to mitigate the region's transportation woes. Cowan has been meeting with American Forests to investigate using CITYgreen and tree planting to improve air quality.
The decline in the ranks of urban forests comes at a time when rural areas are becoming more wooded than they were at the turn of the century, due to a decrease in farming. But today, most people in the United States live in cities and the suburbs being built around them. "We're not against development," says Moll, but "people developing right now are not thinking it's important to keep trees." Moll and other foresters say it's possible to preserve existing trees by building around them, and they encourage homeowners to plant new trees in barren subdivision yards and redeveloped city blocks. With these efforts, the foresters say, the decades-long loss of urban trees can be reversed, and the "invisible" forest will stand strong once again.
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