There are about 326,000 acres of forested or woody wetlands remaining in Maryland. Forested wetlands are highly productive and dynamic environments known as swamps, floodplain forests, riparian areas, bottomland forests, bogs, and pocosins. Characterized by the presence of woody vegetation at least 6 meters tall or taller (NWI), they are found in the eastern United States and in moist parts of the West, especially along rivers and in the mountains.
Forested wetlands are important because they contain a number of diverse habitats and support high numbers of plant and animal species. They filter nutrients (especially nitrogen and phosphorus), wastes, and sediments from water flowing within them. Forested wetlands also provide flood control by stabilizing soils with their extensive root systems and absorbing excessive water. Finally, forested uplands and wetlands sequester carbon dioxide and act as a sink for carbon. According to the most recent National Wetlands Report by the US Fish and Wildlife Service, forested wetlands experienced the greatest decline of all wetland types, with a loss of 1.2 million acres (2.4 percent change). For the first time in the Nation's history, there are fewer than 50 million acres of forested wetlands in the conterminous United States.
The indicator was developed by combining three wetland data sets with National Land Cover Data set (NLCD), to extract wetlands that were covered with forest. The three wetland data sets used were the National Wetlands Inventory (NWI), defined by the U.S. Fish and Wildlife Service and available in 7.5 minute by 7.5 minute blocks; a Department of Natural Resources data set, available in 3.75 minute by 3.75 minute blocks for the time period between 1989 and 1995; and more detailed data for the Nanticoke and Coastal Bays watersheds developed by Ralph Tiner et al in September of 2000.
Watersheds with higher values for this indicator are ones where particular care in forestry practices may be needed in order to maintain the ecological, public safety, and water quality benefits provided by forested wetlands. Because of the history of loss noted above, local land use decision-making may need to be particularly careful about potential impacts of urban types of development proposed in or near forested wetlands.