Prairie Potholes – natural depressions formed by glaciers

Natural wetlands in the upper U.S. and Canada – known as prairie potholes.

Prairie Potholes - natural depressions formed by glaciers 1

These natural depressions formed thousands of years ago by glaciers that scraped over that part of North America. The potholes themselves come in a variety of shapes and sizes. When viewed from above, they look like a mosiac of moon craters.

Like giant sponge, the prairie pothole region soaks up snow melt and rain in the spring and dries out in late summer and fall. So it recycles nutrients very quickly — and that’s why these nutrient-rich wetlands are ideal for the breeding of waterfowl. This region has the highest density of waterfowl breeding pairs in the world for such a large area — only rivaled by dense areas in Alaska.

In the last century, agriculture took its toll on prairie potholes. Here’s Ron Reynolds of the U.S. Fish and Wildlife Services Refuge Program in Bismark, North Dakota.

Reynolds: It’s estimated that about half of the small, shallow wetlands in North and South Dakota have been drained for agricultural production. And when you get over to Minnesota and Iowa, upwards of 95 percent plus of the small, shallow wetlands have been drained.

Praire Pothole Reserves

It’s a myriad of crater-like wetlands that are crucial for the food and cover of waterfowl and other birds. In the last century, many potholes were drained or altered for agricultural or commercial development. It’s estimated that only about half of the original potholes now remain. Dr. Reynolds and his group used waterfowl surveys taken in the 1980s and 1990s to model the impact of the remaining wetlands in terms of the carrying capacity of waterfowl.

Reynolds: We’ve also been involved in studying some farm programs, such as the Conservation Reserve Program, which basically pays land owners a kind of standard rental rate to convert cropland back to grassland.

The Conservation Reserve Program lets up to 36 million acres of farmland nationwide return to wetland. About 7 million of those acres are in the prairie pothole region. Reynolds’ group found that, as a result of this program, about 2 million additional breeding ducks have been raised in the prairie pothole region over what would have been raised otherwise.

Interview about prairie potholes with Ron Reynolds


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