The Prairie Pothole Region (PPR; french: Région des cuvettes/fondrières des prairies) is an expansive area of the northern
Great Plains
The Great Plains (french: Grandes Plaines), sometimes simply "the Plains", is a broad expanse of flatland in North America. It is located west of the Mississippi River and east of the Rocky Mountains, much of it covered in prairie, steppe, an ...
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 ...
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#Glaciology, ablation over many years, often Century, centuries. It acquires dis ...
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 Cor ...
, 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
A moraine is any accumulation of unconsolidated debris (regolith and rock), sometimes referred to as glacial till, that occurs in both currently and formerly glaciated regions, and that has been previously carried along by a glacier or ice shee ...
. These depressions are called potholes, glacial potholes,
kettles, or kettle lakes. They fill with water in the
spring
Spring(s) may refer to:
Common uses
* Spring (season)
Spring, also known as springtime, is one of the four temperate seasons, succeeding winter and preceding summer. There are various technical definitions of spring, but local usage of ...
, 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 Provinces and territories of Canada, province in Western Canada, 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 t ...
,
Manitoba
Manitoba ( ) is a Provinces and territories of Canada, province of Canada at the Centre of Canada, longitudinal centre of the country. It is Canada's Population of Canada by province and territory, fifth-most populous province, with a population o ...
, 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 the ...
,
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 (geometry), direction or geography.
Etymology
T ...
and
South Dakota
South Dakota (; Sioux language, Sioux: , ) is a U.S. state in the West North Central states, North Central region of the United States. It is also part of the Great Plains. South Dakota is named after the Lakota people, Lakota and Dakota peo ...
, 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 Columbi ...
). 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
Surface water is water located on top of land forming terrestrial (inland) waterbodies, and may also be referred to as ''blue water'', opposed to the seawater and waterbodies like the ocean.
The vast majority of surface water is produced by prec ...
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 part ...
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 unconsolidate ...
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 in ...
.
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
''Ranunculus'' is a large genus of about almost 1700 to more than 1800 species of flowering plants in the family Ranunculaceae. Members of the genus are known as buttercups, spearworts and water crowfoots.
The genus is distributed in Europe, ...
, and aquatic
smartweeds are some of the most common. In drier wetlands of the PPR, the vegetation varies from
spikerush
''Eleocharis'' is a virtually cosmopolitan genus of 250 or more species of flowering plants in the sedge family, Cyperaceae. The name is derived from the Greek words ἕλειος (''heleios''), meaning "marsh dweller," and χάρις (''charis' ...
, which is found in the wetter areas of the wetland, to
foxtail barley and
wheatgrass
Wheatgrass is the freshly sprouted first leaves of the common wheat plant (''Triticum aestivum''), used as a food, drink, or dietary supplement. Wheatgrass is served freeze dried or fresh, and so it differs from wheat malt, which is convecti ...
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
North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...
'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 t ...
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
The mallard () or wild duck (''Anas platyrhynchos'') is a dabbling duck that breeds throughout the temperate and subtropical Americas, Eurasia, and North Africa, and has been introduced to New Zealand, Australia, Peru, Brazil, Uruguay, Arge ...
,
gadwall
The gadwall (''Mareca strepera'') is a common and widespread dabbling duck in the family Anatidae.
Taxonomy
The gadwall was first described by Carl Linnaeus in his landmark 1758 10th edition of ''Systema Naturae''. DNA studies have shown that ...
,
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 Scotia ...
,
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 Euro ...
,
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 to ...
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
The Minnesota River ( dak, Mnísota Wakpá) is a tributary of the Mississippi River, approximately 332 miles (534 km) long, in the U.S. state of Minnesota. It drains a watershed of in Minnesota and about in South Dakota and Iowa.
It ris ...
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 E ...
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.
See also
*
Geography of Alberta
Alberta is one of the thirteen provinces and territories of Canada. Located in Western Canada, the province has an area of and is bounded to the south by the United States state of Montana along 49° north for ; to the east at 110° west by t ...
*
Geography of Saskatchewan
The geography of Saskatchewan is unique among the provinces and territories of Canada in some respects. It is one of only two landlocked regions (Alberta is the other) and it is the only region whose borders are not based on natural features li ...
*
Geography of Manitoba
The geography of Manitoba addresses the easternmost of the three prairie Canadian provinces, located in the longitudinal centre of Canada. Manitoba borders on Saskatchewan to the west, Ontario to the east, Nunavut to the north, and the American sta ...
*
Geography of Montana
Montana is one of the eight Mountain States, located in the north of the region known as the Western United States. It borders North Dakota and South Dakota to the east. Wyoming is to the south, Idaho is to the west and southwest, and the Canadia ...
*
Geography of North Dakota
The Geography of North Dakota consists of three major geographic regions: in the east is the Red River Valley, west of this, the Missouri Plateau. The southwestern part of North Dakota is covered by the Great Plains, accentuated by the Badlands. ...
*
Geography of South Dakota
South Dakota is a state located in the north-central United States. It is usually considered to be in the Midwestern region of the country. The state can generally be divided into three geographic regions: eastern South Dakota, western South Dak ...
*
Geography of Minnesota
The U.S. State of Minnesota is the northernmost state outside Alaska; its isolated Northwest Angle in Lake of the Woods is the only part of the 48 contiguous states lying north of the 49th parallel north. Minnesota is in the U.S. region known ...
*
Geography of Iowa
The geography of Iowa includes the study of bedrock, landforms, rivers, geology, paleontology and urbanisation of the U.S. state of Iowa. The state covers an area of 56,272.81 sq mi (145,746 km2).
Bedrock features
Iowa's bedrock geology ge ...
References
External links
*
*
*
America’s Grasslands: A Threatened National TreasureDocumentary 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 StatesUnited 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