23 



insured communities shall prohibit mangrove destruction 

 or lose Federal flood insurance. Extensive mangrove 

 stands protect many coastal communities in Florida. Past 

 destruction of these wetlands for resort housing develop- 

 ments has increased the potential for disaster. Other 

 coastal wetlands and forested wetlands along lakes and 

 large rivers may function similarly. 



Erosion Control 



Located between watercourses and uplands, wetlands 

 help protect uplands from erosion. Wetland vegetation 

 can reduce shoreline erosion in several ways, including: 

 { I ) increasing durability of the sediment through binding 

 with its roots, (2) dampening waves through friction and 

 (3) reducing current velocity through friction (Dean 

 1979). This process also helps reduce turbidity and there- 

 by improves water quality. 



Obviously, trees are good stabilizers of river banks. 

 Their roots bind the soil making it more resistant to ero- 

 sion, while their trunks and branches slow the flow of 

 flooding waters and dampen wave heights. The banks of 

 some rivers have not been eroded for 100 to 200 years due 

 to the presence of trees (Leopold and Wolman 1957; 

 Wolman and Leopold 1957; Sigafoos 1964). Among the 

 grass or grass-like plants, bulrushes and reed have been 

 regarded as the best at withstanding wave and current 

 action (Kadlec and Wentz 1974; Seibert 1968). While 

 most wetland plants need calm or sheltered water for 

 establishment, they will effectively control erosion once 

 established (Kadlec and Wentz 1974; Garbisch 1977). 



Wetland vegetation has been successfully planted to 

 reduce erosion along U.S. waters. Willows, alders, 

 ashes, cottonwoods, poplars, maples and elms are par- 

 ticularly good stabilizers (Allen 1979). Successful emer- 

 gent plants include reed canary grass, reed, cattail, and 

 bulrushes in freshwater areas (Hoffman 1977). Along the 

 Atlantic and Gulf coasts, smooth cordgrass and man- 

 groves have been quite effective (Woodhouse, et al. 

 1976; Lewis and Thomas 1974). 



Water Supply and Groundwater Recharge 



Most wetlands are areas of groundwater discharge and 

 some may provide sufficient quantities of water for public 

 use. In Massachusetts, 40% to 50% of wetlands may be 

 valuable potential sources of drinking water. At least 60 

 municipalities in the state have public wells in or very 

 near wetlands (Motts and Heeley 1973). Urban develop- 

 ment of wetlands and subsequent groundwater withdraw- 

 als have caused saltwater intrusion into aquifers in many 

 coastal areas. Prairie pothole wetlands store water which 

 is important for wildlife and may be used for irrigation 

 and livestock watering by farmers during droughts 

 (Leitch 1981). These situations may hold true for many 



other states and wetland protection could be instrumental 

 in solving current and future water supply problems. 



There is considerable debate over the role of wetlands 

 in groundwater recharge. Recharge potential of wetlands 

 varies according to numerous factors, including wetland 

 type, geographic location, season, soil type, water table 

 location and precipitation. Depressional wetlands like cy- 

 press domes in Florida and prairie potholes in the Dakotas 

 may contribute to groundwater recharge (Odum, et al. 

 1975; Stewart and Kantrud 1972; Winte'r and Carr 1980). 

 Floodplain wetlands also may do this through overbank 

 water storage (Mundorff 1950; Klopatek 1978). Marshes 

 and swamps along the Ipswich River in Massachusetts 

 occasionally operate as recharge areas (U.S. Department 

 of the Interior 1962). 



Harvest of Natural Products 



A variety of natural products are produced by wet- 

 lands, including timber, tish and shellfish, wildlife, peat, 

 cranberries, blueberries, and wild rice. Wetland grasses 

 are hayed in many places for winter livestock feed. Dur- 

 ing other seasons, livestock graze directly in wetlands 

 across the country. These and other products are harvest- 

 ed by man for his use and provide a livelihood for many 

 people. 



In the 49 continental states, an estimated 82 million 

 acres of commercial forested wetlands exist (Johnson 

 1979). These forests provide timber for such uses as 

 homes, furniture, newspapers and firewood. Most of 

 these forests lie east of the Rockies, where trees like oak, 

 gum, cypress, elm, ash and cottonwood are most impor- 

 tant. The standing value of southern wetland forests alone 

 is $8 billion. These southern forests have been harvested 

 for over 200 years without noticeable degradation, thus 

 they can be expected to produce timber for many years to 

 come, unless converted to other uses. Conversion of bot- 

 tomland forests in the Mississippi Delta to agricultural 

 fields (e.g., soybeans) has reduced these wetlands by 

 75% (Giulio 1978; MacDonald, et al. 1979; Frederickson 

 1979). 



Wetlands also produce fish and wildlife for man's use. 

 Commercial fishermen and trappers make a living from 

 these resources (Figure 22). From 1956 to 1975, about 

 60% of the U.S. commercial landings were fishes and 

 shellfishes that depend on wetlands (Peters, et al. 1979). 

 Major commercial species associated with wetlands are 

 menhaden, salmon, shrimp, blue crab and alewife from 

 coastal waters and catfish, carp and buffalo from inland 

 areas. Furs from beaver, muskrat, mink, nutria, and otter 

 yielded roughly $35.5 million in 1976 (Demms and Purs- 

 ley 1978). Louisiana is the largest fur-producing state and 

 nearly all furs come from wetland animals. Freshwater 

 wetlands provide a greater value of fur harvest per acre 

 than estuarine wetlands (Chabreck 1979). 



