Nature’s Sponges: The Importance of Forests in the Bay Watershed

(July 2006) -- Last month's rainfall illustrated how impervious surfaces (such as paved roads, driveways and parking lots) contribute to excess runoff into the Bay. On the other hand, forests play an important role in reducing runoff and nutrient pollution, and this role is being recognized today more than ever.

When Europeans first set foot on the shores of the Bay in the 17 th century, they found diverse, extensive forests covering about 95 percent of the watershed. Today, that number has dropped to about 60 percent, and continues to decline. Since 1982, more than 750,000 acres of forest—equal to the size of 20 Washington, D.C.s—have been lost to new development.

Forests can be compared to sponges; during rainfall events, they:

• Absorb and slowly release the rain, contributing to the majority of the water in our streams and groundwater.
• Hold soil in place with the trees' deep root systems, which stabilize streambanks and reduce erosion.

Forests can also reduce the amount of nutrient pollution that enters the Bay by retaining more than 85 percent of the nitrogen deposited on them from the air. Nitrogen is one of the main nutrients that pollutes the Bay, and scientists have made a direct connection between forestland loss and an increase in nitrogen loads to the water.

This fall the U.S. Forest Service and The Conservation Fund will release the State of the Chesapeake Forests report, which will be a guide to forest conservation efforts in the watershed. Forests are important to the future health of the Bay watershed, and this report will show citizens, governments and environmental groups how best to keep forests thriving in our backyards and beyond.