DC green - News from the World of Trees - Brief Article

American Forests, Spring, 2002

The results are in on a study of tree canopy in a 634-square-mile area in and around Washington, DC. AMERICAN FORESTS used high-resolution satellite imagery and its CITYgreen desktop Geographic Information System software to calculate the tree cover and its overall benefits. The analysis and a "green infrastructure" data layer were created for use by decisionmakers in 103 area communities, including the District of Columbia.

The data show that about 48 percent (177,832 acres) of the DC Metro area is covered by trees (45 percent when federal lands such as national parks are excluded). Impervious surfaces such as buildings, streets, or parking lots make up about 28 percent (108,151 acres), about 17 percent is open space (68,401 acres), 7 percent is bare soil (26,788 acres), and 3 percent is water (10,217 acres).

The District had a 31 percent tree cover when federal lands were included, 22 percent when they were not.

The DC area's urban forest is able to provide 998 million cubic feet in avoided storage of stormwater, a value of $1.96 billion, and remove 19.13 million pounds of pollutants annually, a value of $47.2 million.

The National Capital Planning Commission, U.S. Forest Service, and Casey Trees Endowment Fund sponsored the study, which can be downloaded at www.americanforests.org.

AMERICAN FORESTS will use the high-resolution satellite data and the forthcoming version 5.0 of its CITYgreen software to conduct Urban Ecosystem Analyses this year in: Knox County, Tennessee; San Juan, Puerto Rico; Fayetteville, Arkansas; Philadelphia, Pennsylvania; Roswell, Georgia; San Antonio, Texas; and Roanoke, Virginia.

CITYgreen 5.0 rewrites the product's software code to allow it to analyze larger areas such as watersheds, political boundaries within cities, or entire cities. The new version will run faster, operate more efficiently, and allow users to access other ESRI products such as ArcPad and Spatial Analyst. It also will process a wider variety of images, including aerial photographs and high-resolution satellite images. For info, contact Mike Lehman at 202/955-4500 ext. 212; mlehman@amfor.org.