Wetlands Mapping and Monitoring in the Mid-Atlantic Region

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Wetlands in the Chesapeake Bay watershed perform crucial functions in terms of maintenance of water quality and provision of aquatic habitats, yet they are ecosystems that have been highly modified and are currently threatened by human activities and relative sea level rise. Wetlands, both tidal and non-tidal, are particularly important parts of the landscape, providing crucial incubators for fish and invertebrates, and playing a vital role as habitat for migratory waterfowl. They are, for example, home to approximately one-third of the United States' threatened or endangered plants and animals, and provide refuge to migrating and nesting habitats for over half of the nation's migratory bird species. Wetlands are one of the world's most biologically productive ecosystems and provide a vast economic resource. They are also important for filtering water flows within watersheds, which has implications not only for reducing nutrient and sediment losses but for flood protection, storm water control, maintaining and protecting water supplies, and soil conservation. Wetlands regulate hydrology, for example, by reducing the intensity of floods by holding and gradually releasing stormflows.

Despite these important ecosystem functions and economic benefits, large areas of wetlands have been lost. The conterminous United States has lost over half of its wetlands and Maryland has lost at least 64% (Dahl and Johnson 1991. Wetlands: Status and Trends in the Conterminous United States Mid-1970's to Mid-1980's, U.S Department of the Interior, Fish and Wildlife Service, 28 pages). Assessing the extent and health of wetlands is a mandate for a number of organizations, including the Chesapeake Bay Program , US Fish & Wildlife Service, Environmental Protection Agency, US Geological Survey, State governments encompassing the Chesapeake Bay watershed, the Army Corps of Engineers, and non-Governmental Organizations such as The Chesapeake Bay Foundation, The Nature Conservancy, and World Wildlife Fund, among others. The Chesapeake Bay Program is particularly interested in tracking the status of wetlands and their progress toward restoration. The management goal is not only to reverse the trends in loss, but also to restore wetlands on a net basis.

Mapping and monitoring of wetlands over large areas is greatly facilitated by the use of remotely-sensed imagery. A number of remote sensing applications are being developed by the Mid-Atlantic Regional Earth Science Applications Center, partly for this purpose. The Mid-Atlantic RESAC is analyzing multi-seasonal SAR imagery, in conjunction with Landsat and other data holdings, with the aim of assessing the potential for improved characterization and delineation of wetlands. This effort will be supported by a range of field measurements provided by various RESAC partners. These partners include Jug Bay Wetlands Sanctuary, the Smithsonian Environmental Research Center (SERC), Blackwater National Wildlife Refuge, the Maryland Department of Natural Resources, and Montgomery County, Maryland.

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A substantial amount of SAR imagery is available in the mid-Atlantic region, including JERS and RADARSAT data. Field measurements from study sites shown in this figure are being used to advance research on the utility of SAR data for mapping and monitoring various types of wetlands.