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Prairie Potholes
The prairie potholes of Canada, Minnesota and North and South Dakota were formed by glaciers scraping over the landscape during the Pleistocene.
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Description
Prairie potholes are depressional wetlands (primarily
freshwater marshes)
found most often in the Upper Midwest, especially
North Dakota, South Dakota, Wisconsin, and Minnesota. This formerly glaciated
landscape is pockmarked with an immense number of potholes, which fill with
snowmelt and rain in the spring. Some prairie pothole marshes are temporary,
while others may be essentially permanent. Here a pattern of rough
concentric circles develops. Submerged and floating aquatic plants take over
the deeper water in the middle of the pothole while bulrushes and cattails grow closer to shore.
Wet, sedgy marshes lie next to the upland.
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Western Grebe (Aechmophorus occidentalis)
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Functions & Values
The Upper Midwest, because of its numerous shallow lakes and marshes, rich
soils, and warm summers, is described as being one of the most important
wetland regions in the world. The area is home to more than 50 percent of
North American migratory waterfowl, with many species dependent on the potholes
for breeding and feeding.
In addition to supporting waterfowl hunting and
birding, prairie potholes also absorb surges of rain, snow melt, and floodwaters
thereby reducing the risk and severity of downstream flooding.
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Giant Burreed; Map of prairie pothole region
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More than half of all prairie potholes have been drained or altered for agricultural use.
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Status
Many of these important and highly productive communities have been altered or
destroyed due to increased agricultural and commercial development. As a
result, only an estimated 40 to 50 percent of the region's original prairie
pothole wetlands remain undrained today.
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