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Growing Cities Gain Business, But Lose Trees - 2002-06-16

Throughout the 1990s, business was BOOMING in the United States, and that meant America's cities were booming, as well. Places like Los Angeles, California, Atlanta, Georgia and Washington, D.C. experienced a staggering amount of growth, as businesses and people moved into those regions to take advantage of the prospering economy. All this growth came at a price. America's cities have been losing their trees to development, and now that the trees are gone, many people are realizing how important they are.

In the last 25 years America's cities have lost an average of 30 percent of their tree canopy. In some places such as Atlanta and Washington, D.C., the loss has been as great as 60 percent. Most of the trees have disappeared within the last decade, as areas have been clear-cut to make room for apartment buildings, shopping malls, and all the other hallmarks of economic prosperity.

Sheila Hogan, an environmentalist in Washington, D.C., says the tree loss is creating a water management problem. "In the process of losing half our tree canopy, we have also experienced approximately, a 30 percent increase in storm water runoff, which those trees used to control through their leaves and canopy, and through their root systems," she said. "And with the loss of those trees, we no longer have those benefits. That water tends to just run off the surfaces, all our sidewalks and streets, and go straight down, basically into the Anacostia River."

The Anacostia River, in turn, flows into the Potomac, and on to the Chesapeake Bay, home to more than 300 species of fish. When the storm water runs off streets and sidewalks into the Anacostia, it brings a wide variety of environmental pollutants with it. And that's not the only thing that happens when trees disappear. Cities are also getting hotter. Deborah Gangloff heads an environmental research group called American Forests. She says summer temperatures have gotten particularly bad in Atlanta.

"It's the fastest growing city in the history of the world. And we've watched it creep out into the countryside," she said. "Our analyses of the heat island effect, which is where all the concrete and the pavement holds the day's heat into the night, and essentially raises the average temperature in that city, what happens is the outside countryside is twelve degrees cooler than downtown Atlanta."

That's twelve degrees Fahrenheit, or about half a degree Celsius. Either way, it's a problem in a part of the country that's already known for its extremely high summer temperatures. City officials all over the United States are aware of the impact tree loss is having, and in the last few years, many of them have scrambled to pass laws that limit the number of trees developers can chop down when building malls or housing complexes. But those laws won't replace the trees that have already disappeared. Doing that costs money, and in this sense, Washington, D.C. is in an enviable position.

A philanthropist recently set up a $50 million endowment to replace some of the lost trees in America's capital city. And the first project that endowment has launched is an ambitious effort to identify and catalogue every single tree that already exists along the streets of Washington.

"When you still see the wire in a stake, and you see this, where it's died back, the tree never acclimated to the site, it's dying back."

The Casey Trees Endowment is training about 60 interns to identify trees and assess their condition. The interns are primarily college students, majoring in environmental science and landscape architecture. Throughout the summer, they'll be leading teams of volunteers through Washington, using high-tech global positioning technology to inventory the trees. Kevin Heatly is one of the trainers. He says it's important to know where certain species are so that officials can ensure a high level of diversity when planting new trees.

"We see quite frequently that there's an over-reliance on one or two species," he said. "People look for a magic bullet, and they find something that seems to do well in urban conditions, they plant it, they plant it again, they plant it again, and it does fine, but then geez, twenty years down the line, we find out that these things split easily during storms when they get to be twenty years old, or some new exotic pathogen is brought over from outside the North American area, and we end up with trees dying by entire cities."

Dutch Elm Disease, which basically wiped out the American Elm in the 1940s, is a classic example of why organizers want an inventory of existing trees, before they'll begin planting new ones. They don't want to replace trees destroyed by development with ones that will easily be destroyed by the forces of nature. By the end of this summer, Casey Trees Endowment will have compiled the first, comprehensive tree inventory of a major, American city. Organizers will then present that inventory to officials in Washington, and begin hammering out a plan to replace the city's lost trees with ones that will grow and thrive in an urban environment.