Lifeline for a landscape.

The Baltimore-Washington area is plagued by overdevelopment and sprawl. An ongoing AMERICAN FORESTS study shows just how much.

Thirty years ago, Washington and Baltimore were two distinct cities separated by miles of farms and woodland and scattered pockets of development. Though a navy town and Maryland's seat of government, Annapolis was a relatively sleepy backwater. Today, these cities have all but merged into a single megalopolis. In fact, the U.S. Census Bureau has considered the Baltimore-Washington corridor a single metropolitan area since 1983. Driving south on Interstate 95, it's hard to say where suburban Baltimore ends and suburban Washington begins.

It comes as no surprise then that urban sprawl has reduced the amount of tree cover in the Chesapeake Bay watershed's largest metropolitan area. To find out just how much, AMERICAN FORESTS conducted an ecosystem analysis of the Baltimore-Washington corridor as the first part of an ambitious Regional Ecosystem Analysis. By analyzing satellite images from 1973, 1986, and 1997 using GIS technology, we discovered average tree cover has dropped from 51 percent to 37 percent. But the results also show the impact of that change on the 1.5 million-acre area to be far more significant than a 14 percent loss would indicate.

Less than 30 years ago heavily forested land (areas at least 50 percent covered by tree canopy) comprised 55 percent of the landscape; today that number has dropped to 37 percent (from 820,569 acres to 555,090). More startling is the dramatic increase in developed land (that with less than 20 percent tree cover) from 31 percent to 49 percent (from 462,025 to 732,392 acres).

"The dominant ecological feature here just 30 years ago was heavy forests. Today it is development and lands sparsely covered with trees," says Gary Moll, vice president of AMERICAN FORESTS' Urban Forest Center. "These changes are so large they threaten to undermine many important natural functions performed by forest ecosystems."

Moll expected this trend to be more pronounced in the Baltimore-Washington corridor than in the rest of the region. However, his first look at data from the 11.42 million-acre southeast portion of the Chesapeake watershed (see map insert, below), an area eight times larger than the Baltimore-Washington corridor, shows development and tree-loss trends of a similar magnitude across the region.

The satellite image data show that in 1973 heavily forested land accounted for 55 percent of that land, which includes all of Delaware and a large portion of Maryland and Virginia; today it's dropped to 38 percent. Developed land and land in agriculture have increased from 35 percent to 50 percent.

Next, AMERICAN FORESTS will use CITYgreen software to quantify the dollar benefits of services provided by trees in the area. Those numbers aren't in yet, but they're expected to rival those from last summer's analysis of Washington state's Puget Sound. In that study, AMERICAN FORESTS found the trees lost over a similar period were valued at about $2.4 billion in stormwater management alone. The work they did each year removing pollutants from the air was worth an estimated $95 million (see "In a Land of Water, Dwindling Trees," Autumn 1998).

The change in tree cover has serious implications not only for urban areas and the land but especially for the health of the Chesapeake Bay. Here as throughout the country, polluted runoff from developed areas and from agricultural lands is the primary threat to water quality. Many species of waterfowl and fish - including economically valuable species such as oysters and blue crabs - have declined until they are at or near the lowest populations

In fact, restoring tree cover has been identified by the Chesapeake Bay Program, a project of the US Environmental Protection Agency and state governments, as one of the most cost-effective ways to clean up the Bay. As the implications of AMERICAN FORESTS' analysis are better known, preserving existing tree cover may become even more important.

What's next in our study? In addition to calculating dollar values for trees in the Baltimore-Washington corridor and the larger study region, AMERICAN FORESTS will analyze the changes in tree cover in various parts of the watershed Local analyses are also being conducted in Washington, DC, Virginia's Fairfax County, and in smaller watersheds, including that of the Anacostia River in and around the nation's capital. The larger goal is to analyze the entire Chesapeake Bay watershed, including more than half of Pennsylvania and part of south-central New York. The project is being conducted with the support and cooperation of the U.S. Forest Service and several local partners.

The data can help the nearly 1,000 municipalities in the watershed better incorporate trees in their planning processes. AMERICAN FORESTS is using its CITYgreen software, aerial photographs, and extensive ground-truthing to conduct more detailed analyses at the city block level of some 60 to 80 sites. The Forest Service and AMERICAN FORESTS are planning workshops, training sessions, and software grants to help local governments expand this work into communities. These powerful GIS tools can help determine where strategic tree planting could improve the environment and quality of life throughout the watershed.

A better understanding of tree cover trends will guide AMERICAN FORESTS' Global ReLeaf for the Chesapeake Bay tree-planting campaign. The goal is to plant 1 million trees in the 64,000-square-mile watershed as part of the larger Global ReLeaf 2000 campaign to plant 20 million trees for the new millennium (see Help Your Habitat!). So far, nearly 800,000 trees have been planted with private and public partners, including the National Park Service, Chesapeake Bay Program, Eddie Bauer, Deer Park Spring Water, Mobil, and Exxon.

The bottom line, says Moll: "We've got to do a better job of understanding what changes we have made on the landscape and how we can revitalize it."

To find out how your community can benefit from AMERICAN FORESTS, Chesapeake analysis, contact Alice Ewen at 202/955-4500, ext. 227. For more on the study, visit www.americanforests.org.

HELP YOUR HABITAT!

Drive or live along the Baltimore-Washington corridor and want to help make it a cleaner, greener place to live and drive? Help AMERICAN FORESTS plant trees in one of the following Global ReLeaf Forest ecosystem restoration sites. Every dollar plants a tree and you can specify where you want your trees planted. Call 800/545-TREE or plant trees online at www.americanforests.org:

* Gunpowder Falls State Park: 2 projects to reestablish wildlife habitat.

* Hart-Miller Island: Create habitat for migratory birds and other wildlife.

* Long Green Valley Conservancy: Improve water quality and aquatic habitat, and provide shelter for migrating songbirds.

* Senaca Creek State Park: Decrease stormwater runoff, provide homes for wildlife, and reduce fragmentation that threatens wider-ranging species.

Craig Noble is a contributing editor for American Forests.