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Restoration of Aquatic Ecosystems: Science, Technology, and Public Policy
years ago. Certain aquatic organisms, such as grass shrimp and mummichog, are now thriving in vast numbers, and some species of waterfowl and fish have returned. However, as this committee has pointed out elsewhere, ecosystem restoration involves more than water quality improvement and increased wildlife use.
native, marsh soils, as well as broken glass and other buried trash. Within San Diego Bay and in San Diego County as a whole, only about 10 percent of the natural salt marsh acreage has escaped urban development. The Hackensack Meadowlands site is a second example of restoration efforts undertaken in an extremely disturbed urban setting (see Box 6.3) characterized by widespread changes in tidal flow patterns, extensive deposits of toxic materials, human disturbances, and invasions of undesirable species (Phragmites) . In both these cases, the sites have experienced great damage both locally and to their biological support systems.
SITES WITH INTERMEDIATE DISTURBANCE
Systems with an intermediate degree of disturbance (Figure 6.3) also exist, where either the site or the landscape (but not both) is still intact. Several examples illustrate the variety of challenges facing restoration projects in such sites. Carolina Bay wetlands of the southeastern United States are abundant throughout the southeastern Atlantic Coastal Plain (Prouty, 1952). These isolated elliptical wetlands range in size from less than 50 m to more than 8 km in diameter and may be either only temporarily inundated or permanently flooded. Although they occupy a small areal portion of the landscape, their ecological importance to wetland and semiaquatic organisms is great (Sharitz and Gibbons, 1982). Most of these wetlands have been disturbed, chiefly through ditching and draining to support agricultural usage. Many have been repeatedly plowed and planted or continually grazed by livestock; permanent ponds have been dug in others. Most of these bays are surrounded by agricultural land or managed forests; very few are physically connected with other wetlands (Sharitz and Gibbons, 1982). Reestablishing the hydroperiod by closing ditches or filling artificial ponds and cessation of agricultural use may allow these bays to resume their wetland function (Schalles et al., 1989).