40 * Technologies To Maintain Biological Diversity 



example, increase precipitation, often substan- 

 tially (38). Watershed forests generally reduce 

 soil erosion and thereby help protect down- 

 stream reservoirs, irrigation systems, harbors, 

 and waterways from siltation (45). Coral reefs 

 are productive oases in otherwise unproductive 

 tropical waters. Algae living inside coral polyps 

 enable the corals to build the reefs (8,49). The 

 reefs, in turn, support local fisheries and pro- 

 tect coastlines. 



Wetlands are another example of an ecosys- 

 tem with protective processes linked to eco- 

 nomic output. Millions of waterfowl and other 

 birds of great economic value depend on the 

 diverse North American wetlands — coastal tun- 

 dra wetlands, inland freshwater marshes, prai- 

 rie potholes, coastal saltwater marshes, and 

 mangrove swamps — for breeding, feeding, mi- 

 grating, and overwintering. 



These wetlands also support most commer- 

 cial and recreational fisheries in the United 

 States. About two-thirds of the major U.S. 

 commercial fish, crustacean, and mollusk spe- 

 cies depend on estuaries and salt marshes for 

 spawning and nursery habitat (88,90). Other 

 wetland services include water purification (by 

 removing nutrients, processing organic wastes, 

 and reducing sediment loads), riverbank and 

 shoreline protection, and flood assimilation. 

 Wetlands temporarily store flood waters, reduc- 

 ing flow rates and protecting people and prop- 

 erty downstream from flood and storm damage. 



For example, the U.S. Army Corps of Engi- 

 neers chose protection of 8,500 acres of wet- 

 lands over construction of a reservoir or ex- 

 tensive walls and dikes as the least-cost solution 

 to flooding problems in the Charles River ba- 

 sin in Massachusetts. It was estimated that loss 



,-,•;„,„ ^,t,ji( US. Fish and Wildlife Service— L. Childers 



Ecosystems such as these wetlands have protective and productive functions linked to economic output. 



