One of the reasons for the decline in the Bay's productivity is due to changes that have occurred in land use - in particular, the destruction of wetlands. Historically, wetlands have been viewed as unappealing and useless ecosystems infested with insects, snakes and rodents. As a result of this perception, the Bay watershed experienced substantial losses of wetlands between the mid 1950s and the late 1970s with annual losses averaging over 2,800 acres. In agricultural areas, many wetlands were drained, cleared and put into crop production. In urban areas, other wetlands were filled for houses, industrial facilities, office buildings and sanitary landfills.
Wetlands are the link between the water and the land.
Although most wetlands have standing or flowing water, many are dry for part of the year. For example, estuarine wetlands that are influenced by the tides may be dry twice a day. Several wetland types occur throughout the Chesapeake watershed due to its variability in typography, climate, soil, hydrology, salinity, vegetation, and other factors. Estuarine wetlands are tidally flooded by salt or brackish water and are found chiefly along the shores of the Bay and its tidal rivers. In contrast, palustrine wetlands are freshwater.