43 



ones (i.e., temporarily flooded) are often tilled during dry 

 periods of the natural hydrologic cycle. 



Drought in the Prairie Pothole Region is largely re- 

 sponsible for declines in waterfowl breeding populations. 

 Drainage of potholes may have a similar but more lasting 

 effect on breeding waterfowl. Each pothole drained leads 

 to a further concentration of the breeding waterfowl pop- 

 ulation. This could result in decreased productivity, re- 

 duced size of the breeding population, and/or increased 

 likelihood of diseases like avian cholera and botulism. 

 Wetland drainage also destroys habitats important to in- 

 vertebrates used as food by breeding waterfowl like pin- 

 tail and blue-winged teal (Krapu 1974: Swanson, et al. 

 1974). Moreover, drainage eliminates the flood storage 

 value of pothole depressions, thereby increasing flooding 

 problems as in the James River basin of North Dakota 

 (Sidle 1983). 



Agricultural activities on upland adjacent to potholes 

 have also adversely impacted waterfowl production. Up- 

 land grasses bordering wetlands provide valuable nesting 

 cover for mallard and other dabbling ducks. Conversion 

 of rangeland to cropland, which destroys these nesting 

 areas, has been accelerating. Between 1965 and 1975, 

 approximately one half of the rangeland in the Coteau du 

 Missouri counties of North Dakota were converted to 



cropland (U.S. Fish and Wildlife Service 1984). 



Excavation of ponds (dugouts) in pothole wetlands is 

 also a problem. Out of an estimated 55,855 dugouts in 

 eastern South Dakota in 1976, 77% were in wetland ba- 

 sins or streams (McPhillips, et al. 1983). Excavation and 

 spoil deposition alter wetland hydrology which may re- 

 duce waterfowl usage. More research is needed to evalu- 

 ate potential impacts. 



The Fish and Wildlife Service has been active in pre- 

 serving Prairie Pothole wetlands through acquisition, 

 easement, and other programs. Recently, wetland acqui- 

 sition in North Dakota was stopped for several years by 

 state law. Due to a U.S. Supreme Court ruling against the 

 state for this action, the Service's wetland acquisition is 

 being resumed. The Federal government generally regu- 

 lates filling of pothole wetlands 10 acres in size or larger, 

 yet smaller isolated wetlands are largely unprotected. A 

 1984 settlement agreement between the Corps of Engi- 

 neers and various environmental groups (National Wild- 

 life Federation v. Marsh) provides an opportunity to 

 improve regulation of agricultural conversion of pothole 

 wetlands. The Service's acquisition and easement pro- 

 gram and improved Federal regulation are needed to 

 maintain valuable waterfowl producing wetlands, since 

 pressures continue to convert such areas to agriculture. 



