42 



Prairie Pothole Region's Emergent Wetlands 



Prairie potholes are the most valuable inland marshes 

 for waterfowl production in North America (Figure 39). 

 Although the Pothole Region accounts for only 10% of 

 the continent's waterfowl breeding area, it produces 50% 

 of the duck crop in an average year and more than that in 

 wet years (Smith, et al. 1964). The Prairie Pothole Re- 

 gion extends from south-central Canada to north-central 

 United States, covering about 300,000 square miles with 

 roughly one-third in the United States. Due to glaciation 

 thousands of years ago, the landscape is pock-marked 

 with millions of pothole depressions, mostly less than 

 two feet deep. These pothole wetlands serve as primary 

 breeding grounds for many kinds of ducks including: 

 mallard, pintail, wigeon, gadwall, shoveler, teal, canvas- 

 back, and redhead. For example, in a study area in north- 

 eastern South Dakota, researchers found an average of 

 140 ducks produced per square mile per year (Evans and 

 Black 1956). 



In North and South Dakota, pothole wetlands original- 

 ly covered 7 million acres. Today, only slightly more 

 than 3 million acres remain. Over half have been de- 

 stroyed by agriculture, irrigation and flood control pro- 

 jects (Elliott pers. comm.). Iowa has lost more than 99% 



of its natural marshes (Bishop pers. comm.). Approxi- 

 mately 9 million acres of potholes have been drained in 

 Minnesota (Figures 40 and 41). Since pothole wetlands 

 are surrounded by farmland, they have been drained to 

 create additional cropland, mostly for wheat in the west 

 and com in the east. Drainage in the Dakotas is largely 

 done by open ditching in contrast to both open ditching 

 and tile drainage in Minnesota and Iowa. These ditches 

 drain into intermittent streams or highway right-of-way 

 ditches. Highway ditches have been heavily used by local 

 farmers to help drain wetlands. In western Minnesota 

 alone, nearly 100,000 acres of wetland have been lost in 

 this way (U.S. Fish and Wildlife Service 1975). In addi- 

 tion, stream channelization sponsored by Federal flood 

 control projects, such as the small watershed protection 

 and flood prevention program (P.L. 83-566), have led to 

 accelerated wetland drainage in the Pothole Region as 

 they have elsewhere in the U.S. (Erickson, et al. 1979). 

 Drainage data for the Dakotas and Minnesota obtained 

 from the U.S. Department of Agriculture's Production 

 and Marketing Administration show that 188,000 acres 

 were drained with Federal assistance in 1949 and 1950 

 alone. Countless other acres were privately drained at the 

 same time (Figure 42). Pothole wetland losses are esti- 

 mated at more than 33,000 acres yeariy (Haddock and 

 DeBates 1969). Among the remaining wetlands, the drier 



Fig. 39. Prairie pothole wetlands are the Nation's most valuable waterfowl production areas, (a) aerial view of potholes and fb) blue-winged teal. 



