The Prairie Pothole Region (PPR) is a large area in the northern Great Plains that contains thousands of shallow wetlands called potholes. These potholes were formed by glacier activity during the Wisconsin glaciation, which ended about 10,000 years ago. As the ice melted, it left behind depressions in the ground, created by uneven layers of soil and rock. These depressions are also called glacial potholes, kettles, or kettle lakes. In the spring, these depressions fill with water, forming wetlands that can last from a few weeks to many years. The PPR covers about 800,000 square kilometers and spans three Canadian provinces—Saskatchewan, Manitoba, and Alberta—and five U.S. states—Minnesota, Iowa, North Dakota, South Dakota, and Montana. The water movement in these wetlands varies, which supports long-term productivity and a wide variety of plant and animal life. The PPR is an important place for millions of migrating waterfowl to breed and nest.

Hydrology

Pothole wetlands in the region are not connected by streams, so they do not rely on natural water flow systems. Most of their water comes from melted snow in the spring and rain. Some wetlands also get water from underground sources, which helps them stay wet longer during the year. Wetlands that only receive water from rain usually dry up faster and help add water back into the ground. The way water moves in pothole wetlands changes based on how much rain falls and how much groundwater is available, causing regular cycles of wet and dry periods.

Vegetation

The vegetation in the Prairie Pothole Region (PPR) includes plants that grow above the water, such as tall grasses, and the surrounding prairie has thick grasslands. The types of plants in an area depend greatly on how much water is available. In wetlands that stay wet during the summer, the most common plant is hard-stem bulrush, along with soft-stem bulrush and common threesquare in slightly drier parts of the wetlands. In wetlands that are always flooded, the plants are more aquatic, such as duckweeds, pondweeds, aquatic buttercups, and aquatic smartweeds. In drier wetlands of the PPR, plants vary: spikerush grows in the wetter parts, while foxtail barley and wheatgrass are found near the edges. The amount of water in the PPR changes, but a large seed bank under the soil helps plants survive. During droughts, shortgrass plants grow more, and during wetter times, tallgrass and mixed prairie plants become more common.

Wildlife

The Prairie Pothole Region is home to important habitats for migratory waterfowl and other wildlife. It helps support more than half of North America's migratory waterfowl. This area is one of the most important places in North America where ducks breed. Even though the region covers only about one-tenth of the continent's habitat for breeding waterfowl, about half of the main types of ducks that are hunted on the continent breed there. More than 60% of the breeding populations of mallard, gadwall, blue-winged teal, northern shoveler, northern pintail, redhead, and canvasback ducks live in this region.

Threats

Conversion of land for farming is a major reason for the loss of wetlands in the PPR. More than half of the wetlands have been drained to grow crops. In the Minnesota River basin, 90% of prairie wetlands have been lost as homes for wildlife. The wetlands that remain, which are surrounded by farmland, also face problems. Chemicals, soil, and nutrients from farms flow into these wetlands, causing harm.

Climate change is a serious challenge for the future of PPR wetlands that support ducks and other birds. Without action, severe droughts and higher temperatures will cause many small wetlands called potholes to dry up earlier in spring. Because waterfowl migrate at specific times, these dried wetlands will not provide good places for birds to breed. Droughts linked to warming may affect up to 90% of the PPR's remaining wetlands. Studies show that climate change may move the most productive wetlands from the center of the region (southeastern Saskatchewan and the Dakotas) to the edges in the east and north. However, research also shows that the effects of increased farming and wetland drainage are more important than those of climate change.