Land Use Change and the Chesapeake Bay Ecosystem

The Chesapeake Bay watershed.

The Chesapeake Bay is the largest estuary in North America, encompassing a 168,000 sq. kilometer watershed that covers parts of six states and the District of Columbia. The mixing of salt and freshwater in the Bay creates a diverse and complex ecosystem, which historically has supported thousands of migratory and resident species, including oysters, blue crabs, shad, herring, and waterfowl. The numbers of fish and wildlife that the Bay once supported has diminished drastically due in part to overharvesting and disease, but pollution from urban runoff, agriculture, and inadequate sewage treatment has caused a serious decline in water quality.

Abundance of blue crab reached a historic low in 2002 (Chesapeake Bay Stock Assessment Committee).

Restoration of the Bay has been the focus of a two-decade regional partnership of local, state, and federal agencies, including a network of scientists, politicians and political activists interacting through various committees, working groups, and advisory panels within the Chesapeake Bay Program.  The overall health of the Bay has not declined since the restoration was initiated in 1983, but many of the advances have been offset by the pressure of increasing population and exurban sprawl across the watershed.

The needs of the Chesapeake Bay Program are many, but the greatest is accurate information on land cover and land use change, primarily to assess the implications for water quality, examine various restoration scenarios, and to calibrate spatial models of the urbanization process.  In addition to developing map products to help meet these needs, we conduct applications oriented research to support resource management and decision making in the mid-Atlantic region and the Chesapeake Bay watershed.

We estimate that 504 square kilometers of forest and 1,246 square kilometers of agricultural lands have been lost to development between 1990 and 2000 in the Chesapeake Bay watershed.

Using satellite imagery, we have developed maps of the built environment in the Chesapeake Bay watershed for 1990 and 2000, and land cover/land use maps for 1990 and 2000.  In addition, we have calibrated a model of urban land use change for the Baltimore-Washington, DC area and have produced forecasts of future development out to 2030 under different policy scenarios.  Forecasts of development for Maryland have allowed us to evaluate the threat that development poses to important forest resources.

©Woods Hole Research Center, 2007