The Prairie Pothole Region (PPR; french: Région des cuvettes/fondrières des prairies) is an expansive area of the northern Great Plains that contains thousands of shallow

wetland A wetland is a distinct ecosystem that is flooded or saturated by water, either permanently (for years or decades) or seasonally (for weeks or months). Flooding results in oxygen-free (anoxic) processes prevailing, especially in the soils. The p ...

s known as

potholes A pothole is a depression in a road surface, usually asphalt pavement, where traffic has removed broken pieces of the pavement. It is usually the result of water in the underlying soil structure and traffic passing over the affected area. Water ...

. These potholes are the result of

glacier A glacier (; ) is a persistent body of dense ice that is constantly moving under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. It acquires distinguishing features, such as ...

activity in the

Wisconsin glaciation The Wisconsin Glacial Episode, also called the Wisconsin glaciation, was the most recent glacial period of the North American ice sheet complex. This advance included the Cordilleran Ice Sheet, which nucleated in the northern North American Cord ...

, which ended about 10,000 years ago. The decaying ice sheet left behind depressions formed by the uneven deposition of

till image:Geschiebemergel.JPG, Closeup of glacial till. Note that the larger grains (pebbles and gravel) in the till are completely surrounded by the matrix of finer material (silt and sand), and this characteristic, known as ''matrix support'', is d ...

in ground moraines. These depressions are called potholes, glacial potholes, kettles, or kettle lakes. They fill with water in the spring, creating wetlands, which range in duration from temporary to semi-permanent. The region covers an area of about 800,000 sq. km and expands across three Canadian provinces (

Saskatchewan Saskatchewan ( ; ) is a province in western Canada, bordered on the west by Alberta, on the north by the Northwest Territories, on the east by Manitoba, to the northeast by Nunavut, and on the south by the U.S. states of Montana and North Dak ...

Manitoba , image_map = Manitoba in Canada 2.svg , map_alt = Map showing Manitoba's location in the centre of Southern Canada , Label_map = yes , coordinates = , capital = Winn ...

, and

Alberta Alberta ( ) is one of the thirteen provinces and territories of Canada. It is part of Western Canada and is one of the three prairie provinces. Alberta is bordered by British Columbia to the west, Saskatchewan to the east, the Northwest Ter ...

) and five U.S. states (

Minnesota Minnesota () is a state in the upper midwestern region of the United States. It is the 12th largest U.S. state in area and the 22nd most populous, with over 5.75 million residents. Minnesota is home to western prairies, now given over to ...

Iowa Iowa () is a state in the Midwestern region of the United States, bordered by the Mississippi River to the east and the Missouri River and Big Sioux River to the west. It is bordered by six states: Wisconsin to the northeast, Illinois to th ...

North North is one of the four compass points or cardinal directions. It is the opposite of south and is perpendicular to east and west. ''North'' is a noun, adjective, or adverb indicating direction or geography. Etymology The word ''north ...

and

South Dakota South Dakota (; Sioux: , ) is a U.S. state in the North Central region of the United States. It is also part of the Great Plains. South Dakota is named after the Lakota and Dakota Sioux Native American tribes, who comprise a large porti ...

, and

Montana Montana () is a state in the Mountain West division of the Western United States. It is bordered by Idaho to the west, North Dakota and South Dakota to the east, Wyoming to the south, and the Canadian provinces of Alberta, British Columb ...

). The hydrology of the wetlands is variable, which results in long term productivity and biodiversity. The PPR is a prime spot during breeding and nesting season for millions of migrating waterfowl.

Hydrology

Few natural surface water drainage systems occur in the region as pothole wetlands are not connected by surface streams. They receive most of their water from spring

snowmelt In hydrology, snowmelt is surface runoff produced from melting snow. It can also be used to describe the period or season during which such runoff is produced. Water produced by snowmelt is an important part of the annual water cycle in many par ...

and precipitation. Some pothole wetlands also receive

groundwater Groundwater is the water present beneath Earth's surface in rock and soil pore spaces and in the fractures of rock formations. About 30 percent of all readily available freshwater in the world is groundwater. A unit of rock or an unconsolidated ...

inflow, so they typically last longer each year than those that only receive water from precipitation. Shorter-duration wetlands fed only by precipitation typically are sources of

groundwater recharge Groundwater recharge or deep drainage or deep percolation is a hydrologic process, where water moves downward from surface water to groundwater. Recharge is the primary method through which water enters an aquifer. This process usually occurs ...

. The hydrology of the potholes is very variable, responding to changes in precipitation and groundwater, and results in regular wet-and-dry cycles.

Vegetation

The vegetation of the PPR consists of emergent plants and tall grasses, while the prairie surrounding the region has dense grassland vegetation. The composition of a local plant community is heavily affected by the amount of water available. In wetter wetlands that retain water through the summer, the common plant is hard-stem bulrush, along with soft-stem bulrush and common threesquare in slightly drier regions of the wetlands. The vegetation in permanently flooded wetlands is more aquatic;

duckweeds Lemnoideae is a subfamily of flowering aquatic plants, known as duckweeds, water lentils, or water lenses. They float on or just beneath the surface of still or slow-moving bodies of fresh water and wetlands. Also known as bayroot, they arose ...

, pondweeds, aquatic buttercups, and aquatic smartweeds are some of the most common. In drier wetlands of the PPR, the vegetation varies from spikerush, which is found in the wetter areas of the wetland, to foxtail barley and wheatgrass on the outer edges of the wetland. The variable availability of water in the Prairie Pothole Region is buffered by an abundant seed bank under the soil, comprising species that thrive under different water regimes. During times of drought, shortgrass species increase and expand their range, while during wetter periods, tallgrass and mixed prairie communities become more common.

Wildlife

The Prairie Pothole Region provides important habitats for migratory waterfowl and other wildlife, supporting more than 50% of North America's migratory waterfowl. In particular, the region is one of North America's most important breeding areas for

duck Duck is the common name for numerous species of waterfowl in the family Anatidae. Ducks are generally smaller and shorter-necked than swans and geese, which are members of the same family. Divided among several subfamilies, they are a form ...

s. Although the region contains only about one-tenth of the continent's habitat area for breeding of waterfowl, roughly half the primary species of game ducks on the continent breed there. The region accounts for more than 60% of the breeding populations of mallard, gadwall,

blue-winged teal The blue-winged teal (''Spatula discors'') is a species of bird in the duck, goose, and swan family Anatidae. One of the smaller members of the dabbling duck group, it occurs in North America, where it breeds from southern Alaska to Nova Scoti ...

northern shoveler The northern shoveler (; ''Spatula clypeata''), known simply in Britain as the shoveler, is a common and widespread duck. It breeds in northern areas of Europe and across the Palearctic and across most of North America, wintering in southern E ...

northern pintail The pintail or northern pintail (''Anas acuta'') is a duck species with wide geographic distribution that breeds in the northern areas of Europe and across the Palearctic and North America. It is migratory and winters south of its breeding ...

redhead Red hair (also known as orange hair and ginger hair) is a hair color found in one to two percent of the human population, appearing with greater frequency (two to six percent) among people of Northern or Northwestern European ancestry and ...

, and

canvasback The canvasback (''Aythya valisineria'') is a species of diving duck, the largest found in North America. Taxonomy Scottish-American naturalist Alexander Wilson described the canvasback in 1814. The genus name is derived from Greek ''aithuia'', ...

ducks.

Threats

Conversion of land for

agriculture Agriculture or farming is the practice of cultivating plants and livestock. Agriculture was the key development in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that enabled people t ...

is a significant factor in the loss of wetlands in the PPR. More than half of the wetlands have been drained for farming. In particular, 90% of the prairie wetlands of the Minnesota River basin have been lost as habitat. The wetlands that do persist, surrounded as they are by agricultural lands, are also affected. Chemical runoff, sedimentation, and nutrient flow into the wetlands have adverse impacts.

Climate change In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to ...

is an adverse factor in the long-term viability of PPR wetlands for breeding ducks and other birds. Without mitigation, severe droughts and rising temperatures will cause many pothole wetlands to dry up sooner in the spring. In turn, due to the timing of waterfowl migrations, these dried wetlands will not present suitable breeding habitat. Warming-related drought may affect as much as 90 percent of the PPR's remaining wetlands. Simulations suggest that climate change will shift the most productive wetlands from the center of the region (southeastern Saskatchewan and the Dakotas) to edges of the PPR in the east and north. However, research has suggested that the effect of global warming is overshadowed by that of intensified land use and drainage of wetlands.

References

External links

* * *
America’s Grasslands: A Threatened National Treasure
Documentary produced by

Prairie Public Television Prairie Public Television is a state network of public television stations operated primarily by Prairie Public Broadcasting. It comprises all of the PBS member stations in the U.S. state of North Dakota. The state network is available via fla ...

Land-use Change, Economics, and Rural Well-being in the Prairie Pothole Region of the United States

United States Geological Survey The United States Geological Survey (USGS), formerly simply known as the Geological Survey, is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, ...

{{Regions of the United States Regions of the Western United States Prairies Regions of North Dakota Regions of South Dakota Geography of Alberta Geography of Manitoba Geography of Saskatchewan Geography of Iowa Geography of Minnesota Geography of Montana

Hydrology

Vegetation

Wildlife

Threats

See also

References

External links