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Keeping Trees Thriving In Our Urban Jungle

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Every fall, a small army hits D.C. streets to dig trenches for trees. Environmentalists say trees in the District are important, and not because they make the city a prettier place, but because they clean the air and provide shade and water runoff. City officials aim to have 40 percent of the D.C. covered by tree canopy by 2035. But keeping trees thriving in the District's urban setting can be a real battle.

Environmental reporter Sabri Ben-Achour met with John Thomas, the associate director of the District's Urban Forestry Administration, to talk about the challenges of maintaining trees in the city. Following are highlights of the interview.

Thomas on the benefit of having trees in the city: "For us in an urban environment, there are probably three things that are most important. First is shade, especially in D.C. in the summer. Second is storm water control. They say about three-quarters of an inch of rain is captured in a mature tree, and that reduces the amount of water that ends up in our rivers, which is what is polluting our rivers. And the last thing is air quality. In D.C. we suffer very high asthma rates in kids, and so trees are one of the things that clean our air. And also beauty... trees are just something that we hold in awe."

Thomas on the survival rate of trees in the D.C. area: "Urban street trees, they say they live anywhere from 7 to 10 years or 8 to 15 years, on average. We have about a 9 to 11 percent mortality rate, if you count tree mortality - not things that have been hit by cars, knocked over by people, or stolen. If you take out all those factors, we're looking at about a 9 percent rate."

Thomas on who's responsible for caring for the trees: "In many cities, you're required to do all the work out to the curb, and plant the trees. The city doesn't do any [work]. In D.C., we put the trees in, we take requests, and we inspect the area and decide what's the best species that we know will survive and do well long-term. What we ask for in return is that for the first two years, people join our Canopy Keeper program."

Thomas on common tree-caring mistakes people make: "Mulching too much is bad. It changes the height of the soil, it doesn't allow water into the planting area, and planting too much soil near the truck can cause insects and disease to grow. Another thing is weed eaters. People continue to hit the trees with the weed eaters, and that damages the tree trunk, which reduces its ability to grow. The other thing is just general abuse: bikes being locked to the tree, car doors hitting the tree, piling of trash near the tree... all of those things really lead to the tree's decline."

[Music: "Tie a Yellow Ribbon Round the Old Oak Tree" by Various Artists from Twin Violin Vol. 5]


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