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Wednesday, March 15, 2023

Great Plains

From Wikipedia, the free encyclopedia
https://en.wikipedia.org/wiki/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, and grassland. It is the southern and main part of the Interior Plains, which also include the tallgrass prairie between the Great Lakes and Appalachian Plateau, and the Taiga Plains and Boreal Plains ecozones in Northern Canada. The term Western Plains is used to describe the ecoregion of the Great Plains, or alternatively the western portion of the Great Plains.

The Great Plains lies across both Central United States and Western Canada, encompassing:

The term "Great Plains" usually refers specifically to the United States portion of the ecozone while the Canadian portion is known as the Canadian Prairies. In Canada it covers southeastern Alberta, southern Saskatchewan and a narrow band of southwestern Manitoba, these three provinces collectively known as the "Prairie Provinces". The entire region is known for supporting extensive cattle-ranching and dryland farming.

Grasslands are among the least protected biomes with vast areas having been converted for agricultural purposes and pastures.

Usage

The term "Great Plains" is used in the United States to describe a sub-section of the even more vast Interior Plains physiographic division, which covers much of the interior of North America. It also has currency as a region of human geography, referring to the Plains Indians or the Plains states.[citation needed]

In Canada the term is rarely used; Natural Resources Canada, the government department responsible for official mapping, treats the Interior Plains as one unit consisting of several related plateaus and plains. There is no region referred to as the "Great Plains" in the Atlas of Canada. In terms of human geography, the term prairie is more commonly used in Canada, and the region is known as the Canadian Prairies, Prairie Provinces or simply "the Prairies".

The North American Environmental Atlas, produced by the Commission for Environmental Cooperation, a NAFTA agency composed of the geographical agencies of the Mexican, American, and Canadian governments, uses the "Great Plains" as an ecoregion synonymous with predominant prairies and grasslands rather than as physiographic region defined by topography. The Great Plains ecoregion includes five sub-regions: Temperate Prairies, West-Central Semi-Arid Prairies, South-Central Semi-Arid Prairies, Texas Louisiana Coastal Plains, and Tamaulipas-Texas Semi-Arid Plain, which overlap or expand upon other Great Plains designations.

Extent

The Great Plains near a farming community in central Kansas

The region is about 500 mi (800 km) east to west and 2,000 mi (3,200 km) north to south. Much of the region was home to American bison herds until they were hunted to near extinction during the mid/late-19th century. It has an area of approximately 500,000 sq mi (1,300,000 km2). Current thinking regarding the geographic boundaries of the Great Plains is shown by this map at the Center for Great Plains Studies, University of Nebraska–Lincoln. This definition, however, is primarily ecological, not physiographic. The Boreal Plains of Western Canada are physiographically the same, but differentiated by their tundra and forest (rather than grassland) appearance.

The term "Great Plains", for the region west of about the 96th meridian west and east of the Rocky Mountains, was not generally used before the early 20th century. Nevin Fenneman's 1916 study Physiographic Subdivision of the United States brought the term Great Plains into more widespread usage. Before that the region was almost invariably called the High Plains, in contrast to the lower Prairie Plains of the Midwestern states. Today the term "High Plains" is used for a subregion of the Great Plains. The term still remains little-used in Canada compared to the more common, "prairie".

Geography

Farmland in Sioux and Lyon Counties, Iowa (2013)
 
Dust cloud moving across the Llano Estacado near Ransom Canyon, Texas

The Great Plains are the westernmost portion of the vast North American Interior Plains, which extend east to the Appalachian Plateau. The United States Geological Survey divides the Great Plains in the United States into ten physiographic subdivisions:

Further to this can be added Canadian physiographic sub-regions such as the Alberta Plain, Cypress Hills, Manitoba Escarpment (eastward), Manitoba Plain, Missouri Coteau (shared), Rocky Mountain Foothills (eastward), and Saskatchewan Plain.

The Great Plains consist of a broad stretch of country underlain by nearly horizontal strata extending westward from the 97th meridian west to the base of the Rocky Mountains, a distance of 300 to 500 miles (480 to 800 km). It extends northward from the Mexican boundary far into Canada. Although the altitude of the plains increases gradually from 600 or 1,200 ft (370 m) on the east to 4,000–5,000 or 6,000 feet (1,800 m) near the mountains, the local relief is generally small. The semi-arid climate excludes tree growth and opens far-reaching views.

The plains are by no means a simple unit. They are of diverse structure and of various stages of erosional development. They are occasionally interrupted by buttes and escarpments. They are frequently broken by valleys. Yet on the whole, a broadly extended surface of moderate relief so often prevails that the name, Great Plains, for the region as a whole is well-deserved.

The western boundary of the plains is usually well-defined by the abrupt ascent of the mountains. The eastern boundary of the plains (in the United States) is more climatic than topographic. The line of 20 inches (51 cm) of annual rainfall trends a little east of northward near the 97th meridian. If a boundary must be drawn where nature presents only a gradual transition, this rainfall line may be taken to divide the drier plains from the moister prairies. However, in Canada the eastern boundary of the plains is well defined by the presence of the Canadian Shield to the northeast.

The plains (within the United States) may be described in northern, intermediate, central and southern sections, in relation to certain peculiar features. In Canada, no such division is used: the climatic and vegetation regions are more impactful on human settlement than mere topography, and therefore the region is split into (from north to south), the taiga plains, boreal plains, aspen parkland, and prairie ecoregion regions.

Northern Great Plains

Herd of Plains Bison of various ages resting in Elk Island Park, Alberta
 
The Great Plains as seen in Minnesota's upland prairie at Glacial Lakes State Park

The northern section of the Great Plains, north of latitude 44°, includes eastern Montana, eastern Wyoming, most of North Dakota and South Dakota, southwestern Minnesota and portions of the Canadian provinces including southeastern Alberta, southern Saskatchewan and southwestern Manitoba. The strata here are Cretaceous or early Tertiary, lying nearly horizontal. The surface is shown to be a plain of degradation by a gradual ascent here and there to the crest of a ragged escarpment, the escarpment-remnant of a resistant stratum. There are also the occasional lava-capped mesas and dike formed ridges, surmounting the general level by 500 ft (150 m) or more and manifestly demonstrating the widespread erosion of the surrounding plains. All these reliefs are more plentiful towards the mountains in central Montana. The peneplain is no longer in the cycle of erosion that witnessed its production. It appears to have suffered a regional uplift or increase in elevation, for the upper Missouri River and its branches no longer flow on the surface of the plain, but in well graded, maturely opened valleys, several hundred feet below the general level. A significant exception to the rule of mature valleys occurs, however, in the case of the Missouri, the largest river, which is broken by several falls on hard sandstones about 50 miles (80 km) east of the mountains. This peculiar feature is explained as the result of displacement of the river from a better graded preglacial valley by the Pleistocene ice sheet. Here, the ice sheet overspread the plains from the moderately elevated Canadian highlands far on the north-east, instead of from the much higher mountains nearby on the west. The present altitude of the plains near the mountain base is 4,000 ft (1,200 m).

The northern plains are interrupted by several small mountain areas. The Black Hills, chiefly in western South Dakota, are the largest group. They rise like a large island from the sea, occupying an oval area of about 100 miles (160 km) north-south by 50 miles (80 km) east-west. At Black Elk Peak, they reach an altitude of 7,216 feet (2,199 m) and have an effective relief over the plains of 2000 or 3,000 ft (910 m) This mountain mass is of flat-arched, dome-like structure, now well dissected by radiating consequent streams. The weaker uppermost strata have been eroded down to the level of the plains where their upturned edges are evenly truncated. The next following harder strata have been sufficiently eroded to disclose the core of underlying igneous and metamorphic crystalline rocks in about half of the domed area.

Intermediate Great Plains

In the intermediate section of the plains, between latitudes 44° and 42°, including southern South Dakota and northern Nebraska, the erosion of certain large districts is peculiarly elaborate. Known as the Badlands, it is a minutely dissected form with a relief of a few hundred feet. This is due to several causes:

  • the dry climate, which prevents the growth of a grassy turf
  • the fine texture of the Tertiary strata in the badland districts
  • every little rill, at times of rain, carves its own little valley.

Central Great Plains

The High Plains of Kansas, in the Smoky Hills near Nicodemus

The central section of the Great Plains, between latitudes 42° and 36°, occupying eastern Colorado and western Kansas, is mostly a dissected fluviatile plain. That is, this section was once smoothly covered with a gently sloping plain of gravel and sand that had been spread far forward on a broad denuded area as a piedmont deposit by the rivers which issued from the mountains. Since then, it has been more or less dissected by the erosion of valleys. The central section of the plains thus presents a marked contrast to the northern section.

While the northern section owes its smoothness to the removal of local gravels and sands from a formerly uneven surface by the action of degrading rivers and their inflowing tributaries, the southern section owes its smoothness to the deposition of imported gravels and sands upon a previously uneven surface by the action of aggrading rivers and their outgoing distributaries. The two sections are also alike in that residual eminences still here and there surmount the peneplain of the northern section, while the fluviatile plain of the central section completely buried the pre-existent relief. An exception to this statement must be made for the southwest, close to the mountains in southern Colorado, where some lava-capped mesas (Mesa de Maya, Raton Mesa) stand several thousand feet above the general plain level, and thus testify to the widespread erosion of this region before it was aggraded.

Southern Great Plains

Short-grass prairie near the front range of the Rockies in Colorado
 
View of Lake Lawtonka and wind turbines from Mount Scott, Oklahoma

The southern section of the Great Plains, between latitudes 35.5° and 25.5°, lies in western Texas, eastern New Mexico, and western Oklahoma. Like the central section, it is for the most part a dissected fluviatile plain. However, the lower lands which surround it on all sides place it in such strong relief that it stands up as a table-land, known from the time of Mexican occupation as the Llano Estacado. It measures roughly 150 miles (240 km) east-west and 400 miles (640 km) north-south. It is of very irregular outline, narrowing to the south. Its altitude is 5,500 feet (1,700 m) at the highest western point, nearest the mountains whence its gravels were supplied. From there, it slopes southeastward at a decreasing rate, first about 12 ft (3.7 m), then about 7 ft per mile (1.3 m/km), to its eastern and southern borders, where it is 2,000 feet (610 m) in altitude. Like the High Plains farther north, it is extraordinarily smooth.

It is very dry, except for occasional shallow and temporary water sheets after rains. Llano is separated from the plains on the north by the mature consequent valley of the Canadian River, and from the mountains on the west by the broad and probably mature valley of the Pecos River. On the east, it is strongly undercut by the retrogressive erosion of the headwaters of the Red, Brazos, and Colorado rivers of Texas and presents a ragged escarpment approximately 500 to 800 ft (150 to 240 m) high, overlooking the central denuded area of that state. There, between the Brazos and Colorado rivers, occurs a series of isolated outliers capped by limestone that underlies both the Llano Uplift on the west and the Grand Prairies escarpment on the east. The southern and narrow part of the table-land, called the Edwards Plateau, is more dissected than the rest, and falls off to the south in a frayed-out fault scarp. This scarp overlooks the coastal plain of the Rio Grande embayment. The central denuded area, east of the Llano, resembles the east-central section of the plains in exposing older rocks. Between these two similar areas, in the space limited by the Canadian and Red Rivers, rise the subdued forms of the Wichita Mountains in Oklahoma, the westernmost member of the Ouachita system.

Other terminology

The term "Western Plains" is used to describe the ecoregion of the Great Plains, or alternatively the western portion of the Great Plains.

Natural history

Climate

A tornado touching down in Park County, Colorado, July 23, 2018

In general, the Great Plains have a wide range of weather, with very cold and harsh winters and very hot and humid summers. Wind speeds are often very high, especially in winter.

The 100th meridian roughly corresponds with the line that divides the Great Plains into an area that receives 20 in (510 mm) or more of rainfall per year and an area that receives less than 20 in (510 mm). In this context, the High Plains, as well as Southern Alberta, south-western Saskatchewan and Eastern Montana are mainly semi arid steppe land and are generally characterised by rangeland or marginal farmland. The region (especially the High Plains) is periodically subjected to extended periods of drought; high winds in the region may then generate devastating dust storms. The eastern Great Plains near the eastern boundary falls in the humid subtropical climate zone in the southern areas, and the northern and central areas fall in the humid continental climate.

Many thunderstorms occur in the plains in the spring through summer. The southeastern portion of the Great Plains is the most tornado active area in the world and is sometimes referred to as Tornado Alley.

Flora

The Great Plains are part of the floristic North American Prairies Province, which extends from the Rocky Mountains to the Appalachians.

Fauna

American bison (Bison bison), Wichita Mountain Wildlife Refuge, Oklahoma

Mammals: Although the American bison (Bison bison) historically ranged throughout much of North America (from New York to Oregon and Canada to northern Mexico), they are strongly associated with the Great Plains where they once roamed in immense herds. Pronghorn (Antilocapra americana) range into western areas of the region. The black-tailed prairie dog (Cynomys ludovicianus) is another iconic species among several rodents that are linked to the region including the thirteen-lined ground squirrel (Ictidomys tridecemlineatus), spotted ground squirrel (Xerospermophilus spilosoma), Franklin's ground squirrel (Poliocitellus franklinii), plains pocket gopher (Geomys bursarius), hispid pocket mouse (Chaetodipus hispidus), olive-backed pocket mouse (Perognathus fasciatus), plains pocket mouse (Perognathus flavescens), and plains harvest mouse (Reithrodontomys montanus), Two carnivores associated with the Great Plains include the swift fox (Vulpes velox) and the endangered black-footed ferret (Mustela nigripes).

Birds: The lesser prairie chicken (Tympanuchus pallidicinctus) is endemic to the Great Plains and the distribution of the greater prairie chicken (Tympanuchus cupido) predominantly occurs in the region, although the latter historically ranged further eastward. The Harris's sparrow (Zonotrichia querula) spends winter months in southern areas of the region. Other species migrate from the south in the spring and spend their breeding season on the plains, including the white-faced ibis (Plegadis chihi), mountain plover (Charadrius montanus), marbled godwit (Limosa fedoa), Sprague's pipit (Anthus spragueii), Cassin's sparrow (Peucaea cassinii), Baird's sparrow (Centronyx bairdii), lark bunting (Calamospiza melanocorys), chestnut-collared longspur (Calcarius ornatus), thick-billed longspur or McCown's longspur (Rhynchophanes mccownii), and dickcissel (Spiza americana).

Reptiles: The prairie rattlesnake (Crotalus viridis) ranges throughout much of the Great Plains and into the valleys and lower elevations of the eastern Rocky Mountains and portions of the American southwest. Other snakes include the plains hog-nosed snake (Heterodon nasicus), western milksnake (Lampropeltis gentilis), great plains ratsnake (Pantherophis emoryi), bullsnake (Pituophis catenifer sayi), plains black-headed snake (Tantilla nigriceps), plains gartersnake (Thamnophis radix), and lined snake (Tropidoclonion lineatum). Reptile diversity increases significantly in southern regions of the Great Plains. The ornate box turtle (Terrapene ornata) and great plains skink (Plestiodon obsoletus) occur in southern areas.

Amphibians: Although few salamanders are strongly associated with region, the western tiger salamander (Ambystoma mavortium) ranges through much of the Great Plains and the Rocky Mountains, as does the Rocky Mountain toad (Anaxyrus w. woodhousi). Other anurans related to region include the Great Plains toad (Anaxyrus cognatus), plains leopard frog (Lithobates blairi), and plains spadefoot toad (Spea bombifrons).

Fish: Some species predominately associated with various river basins in the Great Plains include sturgeon chub (Macrhybopsis gelida), peppered chub (Macrhybopsis tetranema), prairie chub (Macrhybopsis australis), western silvery minnow (Hybognathus argyritis), plains minnow (Hybognathus placitus), smalleye shiner (Notropis buccula), Arkansas River shiner (Notropis girardi), Red River shiner (Notropis bairdi), Topeka shiner (Notropis topeka), plains topminnow (Fundulus sciadicus), plains killifish (Fundulus zebrinus), Red River pupfish (Cyprinodon rubrofluviatilis), and Arkansas darter (Etheostoma cragini).

  • Black-footed ferret (Mustela nigripes) National Black-footed Ferret Conservation Center, Colorado

    Black-footed ferret (Mustela nigripes) National Black-footed Ferret Conservation Center, Colorado

  • Swift fox (Vulpes velox), Colorado

    Swift fox (Vulpes velox), Colorado

  • Lesser prairie-chicken (Tympanuchus pallidicinctus) on a lek in the Red Hills of Kansas

    Lesser prairie-chicken (Tympanuchus pallidicinctus) on a lek in the Red Hills of Kansas

  • Great Plains ratsnake (Pantherophis emoryi), Missouri

    Great Plains ratsnake (Pantherophis emoryi), Missouri

  • Great Plains toad (Anaxyrus cognatus)

    Great Plains toad (Anaxyrus cognatus)

Paleontology

Excavation of a fossil Daemonelix burrow at Agate Fossil Beds National Monument.

During the Cretaceous Period (145–66 million years ago), the Great Plains were covered by a shallow inland sea called the Western Interior Seaway. However, during the Late Cretaceous to the Paleocene (65–55 million years ago), the seaway had begun to recede, leaving behind thick marine deposits and a relatively flat terrain which the seaway had once occupied.

During the Cenozoic era, specifically about 25 million years ago during the Miocene and Pliocene epochs, the continental climate became favorable to the evolution of grasslands. Existing forest biomes declined and grasslands became much more widespread. The grasslands provided a new niche for mammals, including many ungulates and glires, that switched from browsing diets to grazing diets. Traditionally, the spread of grasslands and the development of grazers have been strongly linked. However, an examination of mammalian teeth suggests that it is the open, gritty habitat and not the grass itself which is linked to diet changes in mammals, giving rise to the "grit, not grass" hypothesis.

Paleontological finds in the area have yielded bones of mammoths, saber-toothed cats and other ancient animals, as well as dozens of other megafauna (large animals over 100 lb [45 kg]) – such as giant sloths, horses, mastodons, and American lion – that dominated the area of the ancient Great Plains for thousands to millions of years. The vast majority of these animals became extinct in North America at the end of the Pleistocene (around 13,000 years ago).

A number of significant fossil sites are located in the Great Plains including Agate Fossil Beds National Monument (Nebraska), Ashfall Fossil Beds (Nebraska), Clayton Lake State Park (New Mexico), Dinosaur Valley State Park (Texas), Hudson-Meng Bison Kill (Nebraska), Makoshika State Park (Montana), and The Mammoth Site (South Dakota).

Public and protected lands

Scotts Bluff National Monument, Nebraska

Public and protected lands in the Great Plains include National Parks and National Monuments, administers by the National Park Service with the responsibility of preserving ecological and historical places and making them available to the public. The U.S. Fish & Wildlife Service manages the National Wildlife Refuges, with the primary responsibility of conserving and protecting fish, wildlife, plants, and habitat in the public trust. Both are agencies of the Department of the Interior.

In contrast, U.S. Forest Service, an agency of the U. S. Department of Agriculture, administers the National Forests and National Grasslands, under a multiple-use concept. By law, the U.S. Forest Service must consider all resources, with no single resource emphasized to the detriment of others, including water, soil, grazing, timber harvesting, and minerals (mining and drilling), as well as recreation and conservation of fish and wildlife. Each individual state also administers state lands, typically smaller areas, for various purposes including conservation and recreation.

Grasslands are among the least protected biomes. Humans have converted much of the prairies for agricultural purposes or to create pastures. Several of the protected lands in the region are centered around aberrant and uncharacteristic features of the region, such as mountains, outcrops, and canyons (e.g. Devil's Tower National Monument, Wind Cave National Park, Scotts Bluff National Monument), and as splendid and worthy as they are, they are not primarily focused on conserving the plains and prairies.

History

Original American contact

Main article: Plains Indians
See also: Paleo-Indians
 
Buffalo hunt under the wolf-skin mask, George Catlin, 1832–33.

The first Peoples (Paleo-Indians) arrived on the Great Plains thousands of years ago. Historically, the Great Plains were the range of the Blackfoot, Crow, Sioux, Cheyenne, Arapaho, Comanche, and others. Eastern portions of the Great Plains were inhabited by tribes who lived at Etzanoa and in semi-permanent villages of earth lodges, such as the Arikara, Mandan, Pawnee, and Wichita. The introduction of corn around 800 CE allowed the development of the mound-building Mississippian culture along rivers that crossed the Great Plains and that included trade networks west to the Rocky Mountains. Mississippians settled the Great Plains at sites now in Oklahoma and South Dakota.

Siouan language speakers may have originated in the lower Mississippi River region. They were agriculturalists and may have been part of the Mound Builder civilization during the 9th–12th centuries. Wars with the Ojibwe and Cree peoples pushed the Lakota (Teton Sioux) west onto the Great Plains in the mid- to late-17th century. The Shoshone originated in the western Great Basin and spread north and east into present-day Idaho and Wyoming. By 1500, some Eastern Shoshone had crossed the Rocky Mountains into the Great Plains. After 1750, warfare and pressure from the Blackfoot, Crow, Lakota, Cheyenne, and Arapaho pushed Eastern Shoshone south and westward. Some of them moved as far south as Texas, emerging as the Comanche by 1700.

Arrival of horses

Indian family alarmed at the approach of a prairie fire, George Catlin, c. 1846

The first known contact between Europeans and Indians in the Great Plains occurred in what is now Texas, Kansas, and Nebraska from 1540 to 1542 with the arrival of Francisco Vázquez de Coronado, a Spanish conquistador. In that same period, Hernando de Soto crossed a west-northwest direction in what is now Oklahoma and Texas which is now known as the De Soto Trail. The Spanish thought that the Great Plains were the location of the mythological Quivira and Cíbola, a place said to be rich in gold.

People in the southwest began to acquire horses in the 16th century by trading or stealing them from Spanish colonists in New Mexico. As horse culture moved northward, the Comanche were among the first to commit to a fully mounted nomadic lifestyle. This occurred by the 1730s, when they had acquired enough horses to put all their people on horseback.

The real beginning of the horse culture of the plains began with the Pueblo Revolt of 1680 in New Mexico and the capture of thousands of horses and other livestock. In 1683 a Spanish expedition into Texas found horses among Native people. In 1690, a few horses were found by the Spanish among the Indians living at the mouth of the Colorado River of Texas and the Caddo of eastern Texas had a sizeable number.

The French explorer Claude Charles Du Tisne found 300 horses among the Wichita on the Verdigris River in 1719, but they were still not plentiful. Another Frenchman, Bourgmont, could only buy seven at a high price from the Kaw in 1724, indicating that horses were still scarce among tribes in Kansas. By 1770, that Plains Indians culture was mature, consisting of mounted buffalo-hunting nomads from Saskatchewan and Alberta southward nearly to the Rio Grande.

This painting by Alfred Jacob Miller is a portrayal of Plains Indians chasing buffalo over a small cliff. The Walters Art Museum.

The milder winters of the southern Plains favored a pastoral economy by the Indians. On the northeastern Plains of Canada, the Indians were less favored, with families owning fewer horses, remaining more dependent upon dogs for transporting goods, and hunting bison on foot. The scarcity of horses in the north encouraged raiding and warfare in competition for the relatively small number of horses that survived the severe winters.

Comanche power peaked in the 1840s when they conducted large-scale raids hundreds of miles into Mexico proper, while also warring against the Anglo-Americans and Tejanos who had settled in independent Texas.

Fur trade

The fur trade brought thousands of colonial settlers into the Great Plains over the next 100 years. Fur trappers made their way across much of the region, making regular contacts with Indians. The United States acquired the Louisiana Purchase in 1803 and conducted the Lewis and Clark Expedition in 1804–1806, and more information became available concerning the Plains, and various pioneers entered the areas. Fur trading posts were often the basis of later settlements. Through the 19th century, more settlers migrated to the Great Plains as part of a vast westward expansion of population, and new settlements became dotted across the Great Plains.

The settlers also brought diseases against which the Indians had no resistance. Between a half and two-thirds of the Plains Indians are thought to have died of smallpox by the time of the Louisiana Purchase. The 1837 Great Plains smallpox epidemic spread across the Great Plains, killing many thousands between 1837 and 1840. In the end, it is estimated that two-thirds of the Blackfoot population died, along with half of the Assiniboines and Arikaras, a third of the Crows, and a quarter of the Pawnees.

Great Plains in North Dakota c. 2007, where communities began settling in the 1870s.

Pioneer settlement

See also: Cattle drives in the United States
 
Fort William, the first Fort Laramie, as it looked prior to 1840. Painting from memory by Alfred Jacob Miller

Beginning in 1821, the Santa Fe Trail ran from the Missouri River to New Mexico, skirting north of Comancheria. Beginning in the 1830s, the Oregon Trail led from the Missouri River across the Great Plains.

After 1870, the new railroads across the Plains brought hunters who killed off almost all the bison for their hides. The railroads offered attractive packages of land and transportation to American farmers, who rushed to settle the land. They also took advantage of the homestead laws to obtain farms. Land speculators and local boosters identified many potential towns, and those reached by the railroad had a chance, while the others became ghost towns. Towns flourished if they were favored by proximity to the railroad.

Much of the Great Plains became open range where cattle roamed free, hosting ranching operations where anyone was free to run cattle. In the spring and fall, ranchers held roundups where their cowboys branded new calves, treated animals, and sorted the cattle for sale. Such ranching began in Texas and gradually moved northward. Between 1866 and 1895, cowboys herded 10 million cattle north to rail heads such as Dodge City, Kansas and Ogallala, Nebraska; from there, cattle were shipped east.

The U.S. passed the Homestead Acts of 1862 to encourage agricultural development of the Great Plains and house a growing population. It allowed a settler to claim up to 160 acres (65 hectares) of land, provided that he lived on it for a period of five years and cultivated it. The provisions were expanded under the Kinkaid Act of 1904 to include a homestead of an entire section. Hundreds of thousands of people claimed such homesteads, sometimes building houses out of the very turf of the land. Many of them were not skilled farmers, and failures were frequent. The Canadian Dominion Lands Act of 1871 served a similar function for establishing homesteads on the prairies in Canada.

Social life

Grange in session, 1873

The railroads opened up the Great Plains for settlement, making it possible to ship wheat and other crops at low cost to the urban markets in the East and overseas. Homestead land was free for American settlers. Railroads sold their land at cheap rates to immigrants in the expectation that they would generate traffic as soon as farms were established. Immigrants poured in, especially from Germany and Scandinavia. On the plains, very few single men attempted to operate a farm or ranch by themselves; they understood the need for a hard-working wife and numerous children to handle the many responsibilities. During the early years of settlement, farm women played an integral role in assuring family survival by working outdoors. After approximately one generation, women increasingly left the fields, thus redefining their roles within the family. New technology encouraged women to turn to domestic roles, including sewing and washing machines. Media and government extension agents promoted the "scientific housekeeping" movement, along with county fairs which featured achievements in home cookery and canning, advice columns for women regarding farm book keeping, and home economics courses in the schools.

The eastern image of farm life in the prairies emphasized the isolation of the lonely farmer and wife, yet plains residents created busy social lives for themselves. They often sponsored activities which combined work, food, and entertainment, such as barn raisings, corn huskings, quilting bees, Grange meetings, church activities and school functions. Women organized shared meals and potluck events, as well as extended visits among families.

20th century

Withdrawal rates from the Ogallala Aquifer

The region roughly centered on the Oklahoma Panhandle was known as the Dust Bowl during the late 1920s and early 1930s, including southeastern Colorado, southwestern Kansas, the Texas Panhandle, and extreme northeastern New Mexico. The effects of an extended drought, inappropriate cultivation, and financial crises of the Great Depression forced many farmers off the land throughout the Great Plains.

From the 1950s on, many areas of the Great Plains have become productive crop-growing areas because of extensive irrigation on large land-holdings. The United States is a major exporter of agricultural products. The southern portion of the Great Plains lies over the Ogallala Aquifer, a huge underground layer of water-bearing strata. Center pivot irrigation is used extensively in drier sections of the Great Plains, resulting in aquifer depletion at a rate that is greater than the ground's ability to recharge.

Population decline

Main article: Depopulation of the Great Plains
 
Wind farm in the plains of West Texas

The rural Plains have lost a third of their population since 1920. Several hundred thousand square miles of the Great Plains have fewer than 6 inhabitants per square mile (2.3 inhabitants per square kilometer), the density standard that Frederick Jackson Turner used to declare the American frontier "closed" in 1893. Many have fewer than 2 inhabitants per square mile (0.77 inhabitants per square kilometer). There are more than 6,000 ghost towns in Kansas alone, according to Kansas historian Daniel Fitzgerald. This problem is often exacerbated by the consolidation of farms and the difficulty of attracting modern industry to the region. In addition, the smaller school-age population has forced the consolidation of school districts and the closure of high schools in some communities. The continuing population loss has led some to suggest that the current use of the drier parts of the Great Plains is not sustainable, and there has been a proposal to return approximately 139,000 sq mi (360,000 km2) of these drier parts to native prairie land as a Buffalo Commons.

Wind power

The Great Plains contributes substantially to wind power in the United States. T. Boone Pickens developed wind farms after a career as a petroleum executive, and he called for the U.S. to invest $1 trillion to build an additional 200,000 MW of wind power in the Plains as part of his Pickens Plan. He cited Sweetwater, Texas, as an example of economic revitalization driven by wind power development.

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Mammoth steppe

From Wikipedia, the free encyclopedia

Ukok Plateau, one of the last remnants of the mammoth steppe

During the Last Glacial Maximum, the mammoth steppe, also known as steppe-tundra, was the Earth's most extensive biome. It spanned from Spain eastward across Eurasia to Canada and from the arctic islands southward to China. The mammoth steppe was cold and dry. The vegetation was dominated by palatable high-productivity grasses, herbs and willow shrubs. The animal biomass was dominated by reindeer, bison, horses, and woolly mammoth. This ecosystem covered wide areas of the northern part of the globe, thrived for approximately 100,000 years without major changes, but then diminished to small regions around 12,000 years ago.

Naming

At the end of the 19th century, Alfred Nehring (1890) and Jan Czerski (Iwan Dementjewitsch Chersky, 1891) proposed that during the last glacial period a major part of northern Europe had been populated by large herbivores and that a steppe climate had prevailed there. In 1982, the scientist R. Dale Guthrie coined the term "mammoth steppe" for this paleoregion.

Origin

The last glacial period, commonly referred to as the 'Ice Age', spanned from 126,000 YBP–11,700 YBP and was the most recent glacial period within the current ice age which occurred during the last years of the Pleistocene epoch. This arctic environment was very cold and dry and probably dusty, resembling mountaintop environments (alpine tundra), and was very different from today's swampy tundra. It reached its peak during the last glacial maximum, when ice sheets commenced advancing from 33,000 years BP and reached their maximum positions 26,500 years BP. Deglaciation commenced in the Northern Hemisphere approximately 19,000 years BP, and in Antarctica approximately 14,500 years BP, which is consistent with evidence that it was the primary source for an abrupt rise in the sea level at that time.

During the peak of the last glacial maximum, a vast mammoth steppe stretched from the Iberian Peninsula across Eurasia and over the Bering land bridge into Alaska and the Yukon where it was stopped by the Wisconsin glaciation. This land bridge existed because more of the planet's water was locked up in ice than now, hence sea levels were lower. When the sea levels began to rise this bridge was inundated around 11,000 years BP.

During glacial periods, there is clear evidence for intense aridity due to water being held in glaciers and their associated effects on climate. The mammoth steppe was like a huge 'inner court' that was surrounded on all sides by moisture-blocking features: massive continental glaciers, high mountains, and frozen seas. These kept rainfall low and created more days with clear skies than are seen today, which increased evaporation in the summer leading to aridity, and radiation of warmth from the ground into the night sky in winter leading to cold. This is thought to have been caused by seven factors:

  1. The driving force for the core Asian steppe was an enormous and stable high-pressure system north of the Tibetan Plateau.
  2. Deflection of the larger portion of the Gulf Stream southward, past southern Spain onto the coast of Africa, reduced temperatures (hence moisture and cloud cover) that the North Atlantic Current brings to Western Europe.
  3. Growth of the Scandinavian ice sheet created a barrier to North Atlantic moisture.
  4. Icing over of the North Atlantic sea surface with reduced flow of moisture from the east.
  5. The winter (January) storm track seems to have swept across Eurasia on this axis.
  6. Lowered sea levels exposed a large continental shelf to the north and east producing a vast northern plain which increased the size of the continent to the north.
  7. North American glaciers shielded interior Alaska and the Yukon Territory from moisture flow.

These physical barriers to moisture flow created a vast arid basin spanning three continents.

Environment (or biota)

Climatic suitability for the woolly mammoths in the Late Pleistocene and Holocene. Increasing intensities of red represent increasing suitability of the climate and increasing intensities of green represent decreasing suitability. Black points are the records of mammoth presence for each of the periods. Black lines represent the northern limit of modern humans and black dotted lines indicate uncertainty in the limit of modern humans (D. Nogués-Bravo et al. 2008).

Animal biomass and plant productivity of the mammoth steppe were similar to today's African savanna. There is no comparison to it today.

Plants

The paleo-environment changed across time, a proposal that is supported from mammoth dung samples found in northern Yakutia. During Pleniglacial interstadials, alder, birch, and pine trees survived in northern Siberia, however during the Last Glacial Maximum only a treeless steppe vegetation existed. At the onset of the Late Glacial Interstadial (15,000–11,000 BP), global warming resulted in shrub and dwarf birch in northeastern Siberia, which was then colonized by open woodland with birch and spruce during the Younger Dryas (12,900–11,700 YBP). By the Holocene (10,000 YBP), patches of closed larch and pine forests developed. Researchers had previously concluded that the mammoth steppe must have been very unproductive because they assumed that its soils had a very low carbon content; however, these soils (yedoma) were preserved in the permafrost of Siberia and Alaska and are the largest reservoir of organic carbon known. It was a highly productive environment. The vegetation was dominated by palatable high-productivity grasses, herbs and willow shrubs. Herbs were far more widespread than they are today, and were the main food source of the large plant eating mammals.

  • Artemisia, Taymyr lowlands 24,000–10,300 YBP,[25] Yakutia 22,500 YBP,[22] Alaska and the Yukon 15,000-11,500 YBP[21][6]

    Artemisia, Taymyr lowlands 24,000–10,300 YBP, Yakutia 22,500 YBP, Alaska and the Yukon 15,000-11,500 YBP

  • Cyperaceae (sedges), Yakutia 22,500 YBP,[22] Alaska and the Yukon 15,000-11,500 YBP[21][6]

    Cyperaceae (sedges), Yakutia 22,500 YBP, Alaska and the Yukon 15,000-11,500 YBP

  • Gramineae (grasses), Taymyr lowlands 24,000–10,300 YBP,[25] Yakutia 22,500 YBP,[22] Alaska and the Yukon 15,000-11,500 YBP[21][6]

    Gramineae (grasses), Taymyr lowlands 24,000–10,300 YBP, Yakutia 22,500 YBP, Alaska and the Yukon 15,000-11,500 YBP

  • Salix (willow), Taymyr lowlands 24,000–10,300 YBP,[25] Yakutia 22,500 YBP,[22] Alaska and the Yukon 15,000-11,500 YBP[21][6]

    Salix (willow), Taymyr lowlands 24,000–10,300 YBP, Yakutia 22,500 YBP, Alaska and the Yukon 15,000-11,500 YBP

  • Rubus chamaemorus (cloudberry) Yakutia 22,500 YBP[22]

    Rubus chamaemorus (cloudberry) Yakutia 22,500 YBP

  • Potentilla (cinquefoil) Yakutia 22,500 YBP[22]

    Potentilla (cinquefoil) Yakutia 22,500 YBP

  • Larch Taymyr lowlands 48,000–25,000 YBP, then later 9,400-2,900 YBP[25]

    Larch Taymyr lowlands 48,000–25,000 YBP, then later 9,400-2,900 YBP

  • Betula nana (dwarf birch) Taymyr lowlands 48,000–25,000 YBP[25]

    Betula nana (dwarf birch) Taymyr lowlands 48,000–25,000 YBP

Animals

Further information: Woolly mammoth and Woolly rhinoceros
 
Many giant mammals such as woolly mammoths, woolly rhinoceroses, and cave lions inhabited the mammoth steppe during the Pleistocene.

The mammoth steppe was dominated in biomass by reindeer, bison, horse, and the woolly mammoth, and was the center for the evolution of the Pleistocene woolly fauna. Megaloceros, saiga antelope and musk ox also lived on the mammoth steppe (the first one not in the northernmost parts). In the Siberian parts were animals like the argali, Snow sheep and the Mongolian gazelle. Not so far before the last glacial maximum (roughly 40.000 years ago), an extinct paleospecies of argali (Ovis argaloides) lived also in Europe. Notable carnivores found across the whole range of the mammoth steppe included Panthera spelaea, the Wolverine, the wolf Canis lupus and the brown bear Ursus arctos. While the cave hyena was part of mammoth steppe faunas in Europe, it did not extend into the core high latitude north Asian range of the biome. Bird remains are rare because of their fragile structure, but there is some evidence for snowy owl, willow ptarmigan, gyrfalcon, common raven and great bustard. Other bird species are white-tailed eagle and golden eagle. Vultures like griffon vulture and cinereous vulture are not known but they were likely common scavengers on the mammoth steppe, following the large herds and scavenging on dead animals. On Wrangel Island, the remains of woolly mammoth, woolly rhinoceros, horse, bison and musk ox have been found. Reindeer and small animal remains do not preserve, but reindeer excrement has been found in sediment. Small animals on the mammoth steppe were, for example, steppe pika, ground squirrels and alpine marmot. In the most arid regions of the mammoth steppe that were to the south of Central Siberia and Mongolia, woolly rhinoceros were common but woolly mammoths were rare. Reindeer live in the far north of Mongolia today and historically their southern boundary passed through Germany and along the steppes of eastern Europe, indicating they once covered much of the mammoth steppe.

Mammoths survived on the Taimyr Peninsula until the Holocene. A small population of mammoths survived on St. Paul Island, Alaska, up until 3750 BC, and the small mammoths of Wrangel Island survived until 1650 BC. Bison in Alaska and the Yukon, and horses and muskox in northern Siberia, have survived the loss of the mammoth steppe. One study has proposed that a change of suitable climate caused a significant drop in the mammoth population size, which made them vulnerable to hunting from expanding human populations. The coincidence of both of these impacts in the Holocene most likely set the place and time for the extinction of the woolly mammoth.

Decline of the mammoth steppe

The mammoth steppe had a cold, dry climate. During the past interglacial warmings, forests of trees and shrubs expanded northward into the mammoth steppe, when northern Siberia, Alaska and the Yukon (Beringia) would have formed a mammoth steppe refugium. When the planet grew colder again, the mammoth steppe expanded. This ecosystem covered wide areas of the northern part of the globe, thrived for approximately 100,000 years without major changes, but then diminished to small regions around 12,000 years ago.

There are two theories about the decline of the mammoth steppe.

Climate change

The Climatic Hypothesis assumes that the vast mammoth ecosystem could have only existed within a certain range of climatic parameters. At the beginning of the Holocene 10,000 years ago, mossy forests, tundra, lakes and wetlands displaced mammoth steppe. It has been assumed that in contrast to other previous interglacials the cold dry climate switched to a warmer wetter climate that, in turn, caused the disappearance of the grasslands and their dependent megafauna.

The extinct steppe bison (Bison priscus) survived across the northern region of central eastern Siberia until 8000 years ago. A study of the frozen mummy of a steppe bison found in northern Yakutia, Russia indicated that it was a pasture grazer in a habitat that was becoming dominated by shrub and tundra vegetation. Higher temperature and rainfall led to a decrease in its previous habitat during the early Holocene, and this led to population fragmentation followed by extinction.

The mammoth steppe was covered all winter with snow, which reflected sunlight back up into space and thus delayed the spring warming. With no more mammoths left to push trees down to get at their leaves to eat, the area became covered in tall forest sticking up above the snow all winter and catching the early sunlight and thus causing an early spring warming.

In 2017 a study looked at the environmental conditions across Europe, Siberia and the Americas from 25,000 to 10,000 YBP. The study found that prolonged warming events leading to deglaciation and maximum rainfall occurred just before the transformation of the rangelands that supported megaherbivores into widespread wetlands that supported herbivore-resistant plants. The study proposes that moisture-driven environmental change led to the megafaunal extinctions, and that Africa's trans-equatorial position allowed rangeland to continue to exist between the deserts and the central forests; therefore fewer megafauna species became extinct there.

Human predation

The Ecosystem Hypothesis assumes that the vast mammoth ecosystem extended over a range of many regional climates and was not affected by climate fluctuations. Its highly productive grasslands were maintained by animals trampling any mosses and shrubs, and actively transpiring grasses and herbs dominated. At the beginning of the Holocene the rise in precipitation was accompanied by increased temperature, and so its climatic aridity did not change substantially. As a result of human hunting, the decreasing density of the mammoth ecosystem animals was not enough to stop forest from spreading over the grasslands, leading to an increase in forests, shrubs and mosses with further animal reduction due to loss of feed. The mammoth continued to exist on isolated Wrangel Island until a few thousand years ago, and some of the other megafauna from that time still exist today, which indicates that something other than climate change was responsible for megafaunal extinctions.

Remains of mammoth that had been hunted by humans 45,000 YBP have been found at Yenisei Bay in the central Siberian Arctic. Two other sites in the Maksunuokha River valley to the south of the Shirokostan Peninsula, northeast Siberia, dated between 14,900 and 13,600 years ago showed the remains of mammoth hunting and the production of micro-blades similar to those found in northwest North America, suggesting a cultural connection.

Last remnants

Ubsunur Hollow Biosphere Reserve located on the border of Mongolia and the Republic of Tuva is one of the last remnants of the mammoth steppe

During the Holocene, the arid-adapted species became extinct or were reduced to minor habitats. Cold and dry conditions similar to the last glacial period are found today in the eastern Altai-Sayan mountains of Central Eurasia, with no significant changes occurring between the cold phase of the Pleistocene and the Holocene. Recent paleo-biome reconstruction and pollen analysis suggest that some present-day Altai-Sayan areas could be considered the closest analogy to the mammoth steppe environment. The environment of this region is considered to have been stable for the past 40,000 years. The Eastern part of the Altai-Sayan region forms a Last Glacial refugium. In both the Last Glacial and modern times, the eastern Altai-Sayan region has supported large herbivore and predator species adapted to the steppe, desert and alpine biomes where these biomes have not been separated by forest belts. None of the surviving Pleistocene mammals live in temperate forest, taiga, or tundra biomes. The areas of Ukok-Sailiugem in the southern Altai Republic, and Khar Us Nuur and Uvs Nuur (Ubsunur Hollow) in western Mongolia, have supported reindeer and saiga antelope since the glacial period.

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Tundra

From Wikipedia, the free encyclopedia
https://en.wikipedia.org/wiki/Tundra

Tundra
Greenland scoresby-sydkapp2 hg.jpg
Tundra in Greenland
 
800px-Map-Tundra.png
Map showing Arctic tundra
 
Geography
Area11,563,300 km2 (4,464,600 sq mi)
Climate typeET

In physical geography, tundra (/ˈtʌndrə, ˈtʊn-/) is a type of biome where tree growth is hindered by frigid temperatures and short growing seasons. The term tundra comes through Russian тундра (tundra) from the Kildin Sámi word тӯндар (tūndâr) meaning "uplands", "treeless mountain tract". There are three regions and associated types of tundra: Arctic tundra, alpine tundra, and Antarctic tundra.

Tundra vegetation is composed of dwarf shrubs, sedges, grasses, mosses, and lichens. Scattered trees grow in some tundra regions. The ecotone (or ecological boundary region) between the tundra and the forest is known as the tree line or timberline. The tundra soil is rich in nitrogen and phosphorus. The soil also contains large amounts of biomass and decomposed biomass that has been stored as methane and carbon dioxide in the permafrost, making the tundra soil a carbon sink. As global warming heats the ecosystem and causes soil thawing, the permafrost carbon cycle accelerates and releases much of these soil-contained greenhouse gases into the atmosphere, creating a feedback cycle that increases climate change.

Arctic

See also: Arctic vegetation

Arctic tundra occurs in the far Northern Hemisphere, north of the taiga belt. The word "tundra" usually refers only to the areas where the subsoil is permafrost, or permanently frozen soil. (It may also refer to the treeless plain in general so that northern Sápmi would be included.) Permafrost tundra includes vast areas of northern Russia and Canada. The polar tundra is home to several peoples who are mostly nomadic reindeer herders, such as the Nganasan and Nenets in the permafrost area (and the Sami in Sápmi).

Tundra in Siberia

Arctic tundra contains areas of stark landscape and is frozen for much of the year. The soil there is frozen from 25 to 90 cm (10 to 35 in) down, making it impossible for trees to grow. Instead, bare and sometimes rocky land can only support certain kinds of Arctic vegetation, low-growing plants such as moss, heath (Ericaceae varieties such as crowberry and black bearberry), and lichen.

There are two main seasons, winter and summer, in the polar tundra areas. During the winter it is very cold, dark, and windy with the average temperature around −28 °C (−18 °F), sometimes dipping as low as −50 °C (−58 °F). However, extreme cold temperatures on the tundra do not drop as low as those experienced in taiga areas further south (for example, Russia's and Canada's lowest temperatures were recorded in locations south of the tree line). During the summer, temperatures rise somewhat, and the top layer of seasonally-frozen soil melts, leaving the ground very soggy. The tundra is covered in marshes, lakes, bogs, and streams during the warm months. Generally daytime temperatures during the summer rise to about 12 °C (54 °F) but can often drop to 3 °C (37 °F) or even below freezing. Arctic tundras are sometimes the subject of habitat conservation programs. In Canada and Russia, many of these areas are protected through a national Biodiversity Action Plan.

Vuntut National Park in Canada

Tundra tends to be windy, with winds often blowing upwards of 50–100 km/h (30–60 mph). However, it is desert-like, with only about 150–250 mm (6–10 in) of precipitation falling per year (the summer is typically the season of maximum precipitation). Although precipitation is light, evaporation is also relatively minimal. During the summer, the permafrost thaws just enough to let plants grow and reproduce, but because the ground below this is frozen, the water cannot sink any lower, so the water forms the lakes and marshes found during the summer months. There is a natural pattern of accumulation of fuel and wildfire which varies depending on the nature of vegetation and terrain. Research in Alaska has shown fire-event return intervals (FRIs) that typically vary from 150 to 200 years, with dryer lowland areas burning more frequently than wetter highland areas.

A group of muskoxen in Alaska

The biodiversity of tundra is low: 1,700 species of vascular plants and only 48 species of land mammals can be found, although millions of birds migrate there each year for the marshes. There are also a few fish species. There are few species with large populations. Notable plants in the Arctic tundra include blueberry (Vaccinium uliginosum), crowberry (Empetrum nigrum), reindeer lichen (Cladonia rangiferina), lingonberry (Vaccinium vitis-idaea), and Labrador tea (Rhododendron groenlandicum). Notable animals include reindeer (caribou), musk ox, Arctic hare, Arctic fox, snowy owl, ptarmigan, northern red-backed voles, lemmings, the mosquito, and even polar bears near the ocean. Tundra is largely devoid of poikilotherms such as frogs or lizards.

Due to the harsh climate of Arctic tundra, regions of this kind have seen little human activity, even though they are sometimes rich in natural resources such as petroleum, natural gas, and uranium. In recent times this has begun to change in Alaska, Russia, and some other parts of the world: for example, the Yamalo-Nenets Autonomous Okrug produces 90% of Russia's natural gas.

Relationship to global warming

A severe threat to tundra is global warming, which causes permafrost to thaw. The thawing of the permafrost in a given area on human time scales (decades or centuries) could radically change which species can survive there. It also represents a significant risk to infrastructure built on top of permafrost, such as roads and pipelines.

In locations where dead vegetation and peat have accumulated, there is a risk of wildfire, such as the 1,039 km2 (401 sq mi) of tundra which burned in 2007 on the north slope of the Brooks Range in Alaska. Such events may both result from and contribute to global warming.

Greenhouse gas emissions

Carbon emissions from permafrost thaw contribute to the same warming which facilitates the thaw, making it a positive climate change feedback. The warming also intensifies Arctic water cycle, and the increased amounts of warmer rain are another factor which increases permafrost thaw depths. The amount of carbon that will be released from warming conditions depends on depth of thaw, carbon content within the thawed soil, physical changes to the environment and microbial and vegetation activity in the soil. Microbial respiration is the primary process through which old permafrost carbon is re-activated and enters the atmosphere. The rate of microbial decomposition within organic soils, including thawed permafrost, depends on environmental controls, such as soil temperature, moisture availability, nutrient availability, and oxygen availability. In particular, sufficient concentrations of iron oxides in some permafrost soils can inhibit microbial respiration and prevent carbon mobilization: however, this protection only lasts until carbon is separated from the iron oxides by Fe-reducing bacteria, which is only a matter of time under the typical conditions. Depending on the soil type, Iron(III) oxide can boost oxidation of methane to carbon dioxide in the soil, but it can also amplify methane production by acetotrophs: these soil processes are not yet fully understood.

Altogether, the likelihood of the entire carbon pool mobilizing and entering the atmosphere is low despite the large volumes stored in the soil. Although temperatures will increase, this does not imply complete loss of permafrost and mobilization of the entire carbon pool. Much of the ground underlain by permafrost will remain frozen even if warming temperatures increase the thaw depth or increase thermokarsting and permafrost degradation. Moreover, other elements such as iron and aluminum can adsorb some of the mobilized soil carbon before it reaches the atmosphere, and they are particularly prominent in the mineral sand layers which often overlay permafrost. On the other hand, once the permafrost area thaws, it will not go back to being permafrost for centuries even if the temperature increase reversed, making it one of the best-known examples of tipping points in the climate system.

In 2011, preliminary computer analyses suggested that permafrost emissions could be equivalent to around 15% of anthropogenic emissions.

A 2018 perspectives article discussing tipping points in the climate system activated around 2 degrees Celsius of global warming suggested that at this threshold, permafrost thaw would add a further 0.09 °C to global temperatures by 2100, with a range between 0.04 °C and 0.16 °C In 2021, another study estimated that in a future where zero emissions were reached following a emission of a further 1000 Pg C into the atmosphere (a scenario where temperatures ordinarily stay stable after the last emission, or start to decline slowly) permafrost carbon would add 0.06 °C (with a range between 0.02 °C and 0.14 °C) 50 years after the last anthropogenic emission, 0.09 °C (with a range between 0.04 °C to 0.21 °C) 100 years later and 0.27 °C (ranging between 0.12 to 0.49 °C) 500 years later. However, neither study was able to take abrupt thaw into account.

In 2020, a study of the northern permafrost peatlands (a smaller subset of the entire permafrost area, covering 3.7 million km2 out of the estimated 18 million km2) would amount to ∼1% of anthropogenic radiative forcing by 2100, and that this proportion remains the same in all warming scenarios considered, from 1.5 °C to 6 °C. It had further suggested that after 200 more years, those peatlands would have absorbed more carbon than what they had emitted into the atmosphere.

The IPCC Sixth Assessment Report estimates that carbon dioxide and methane released from permafrost could amount to the equivalent of 14–175 billion tonnes of carbon dioxide per 1 ºC of warming.  For comparison, by 2019 the anthropogenic emission of all carbon dioxide into the atmosphere stood around 40 billion tonnes.

A 2021 assessment of the economic impact of climate tipping points estimated that permafrost carbon emissions would increase the social cost of carbon by about 8.4%  However, the methods of that assessment have attracted controversy: when researchers like Steve Keen and Timothy Lenton had accused it of underestimating the overall impact of tipping points and of higher levels of warming in general, the authors have conceded some of their points.

In 2021, a group of prominent permafrost researchers like Merritt Turetsky had presented their collective estimate of permafrost emissions, including the abrupt thaw processes, as part of an effort to advocate for a 50% reduction in anthropogenic emissions by 2030 as a necessary milestone to help reach net zero by 2050. Their figures for combined permafrost emissions by 2100 amounted to 150–200 billion tonnes of carbon dioxide equivalent under 1.5 degrees of warming, 220–300 billion tonnes under 2 degrees and 400–500 billion tonnes if the warming was allowed to exceed 4 degrees. They compared those figures to the extrapolated present-day emissions of Canada, the European Union and the United States or China, respectively. The 400–500 billion tonnes figure would also be equivalent to the today's remaining budget for staying within a 1.5 degrees target. One of the scientists involved in that effort, Susan M. Natali of Woods Hole Research Centre, had also led the publication of a complementary estimate in a PNAS paper that year, which suggested that when the amplification of permafrost emissions by abrupt thaw and wildfires is combined with the foreseeable range of near-future anthropogenic emissions, avoiding the exceedance (or "overshoot") of 1.5 degrees warming is already implausible, and the efforts to attain it may have to rely on negative emissions to force the temperature back down.

An updated 2022 assessment of climate tipping points concluded that abrupt permafrost thaw would add 50% to gradual thaw rates, and would add 14 billion tons of carbon dioxide equivalent emissions by 2100 and 35 by 2300 per every degree of warming. This would have a warming impact of 0.04 °C per every full degree of warming by 2100, and 0.11 °C per every full degree of warming by 2300. It also suggested that at between 3 and 6 degrees of warming (with the most likely figure around 4 degrees) a large-scale collapse of permafrost areas could become irreversible, adding between 175 and 350 billion tons of CO2 equivalent emissions, or 0.2–0.4 degrees, over about 50 years (with a range between 10 and 300 years).

Antarctic

Tundra on the Kerguelen Islands.

Antarctic tundra occurs on Antarctica and on several Antarctic and subantarctic islands, including South Georgia and the South Sandwich Islands and the Kerguelen Islands. Most of Antarctica is too cold and dry to support vegetation, and most of the continent is covered by ice fields. However, some portions of the continent, particularly the Antarctic Peninsula, have areas of rocky soil that support plant life. The flora presently consists of around 300–400 species of lichens, 100 mosses, 25 liverworts, and around 700 terrestrial and aquatic algae species, which live on the areas of exposed rock and soil around the shore of the continent. Antarctica's two flowering plant species, the Antarctic hair grass (Deschampsia antarctica) and Antarctic pearlwort (Colobanthus quitensis), are found on the northern and western parts of the Antarctic Peninsula. In contrast with the Arctic tundra, the Antarctic tundra lacks a large mammal fauna, mostly due to its physical isolation from the other continents. Sea mammals and sea birds, including seals and penguins, inhabit areas near the shore, and some small mammals, like rabbits and cats, have been introduced by humans to some of the subantarctic islands. The Antipodes Subantarctic Islands tundra ecoregion includes the Bounty Islands, Auckland Islands, Antipodes Islands, the Campbell Island group, and Macquarie Island. Species endemic to this ecoregion include Corybas dienemus and Corybas sulcatus, the only subantarctic orchids; the royal penguin; and the Antipodean albatross.

There is some ambiguity on whether Magellanic moorland, on the west coast of Patagonia, should be considered tundra or not. Phytogeographer Edmundo Pisano called it tundra (Spanish: tundra Magallánica) since he considered the low temperatures key to restrict plant growth.

The flora and fauna of Antarctica and the Antarctic Islands (south of 60° south latitude) are protected by the Antarctic Treaty.

Alpine

Main article: Alpine tundra
 
Alpine tundra in the North Cascades of Washington, United States

Alpine tundra does not contain trees because the climate and soils at high altitude block tree growth. The cold climate of the alpine tundra is caused by the low air temperatures, and is similar to polar climate. Alpine tundra is generally better drained than arctic soils. Alpine tundra transitions to subalpine forests below the tree line; stunted forests occurring at the forest-tundra ecotone (the treeline) are known as Krummholz.

Alpine tundra occurs in mountains worldwide. The flora of the alpine tundra is characterized by plants that grow close to the ground, including perennial grasses, sedges, forbs, cushion plants, mosses, and lichens. The flora is adapted to the harsh conditions of the alpine environment, which include low temperatures, dryness, ultraviolet radiation, and a short growing season.

Climatic classification

Main articles: Tundra climate and Alpine climate
 
Tundra region with fjords, glaciers and mountains. Kongsfjorden, Spitsbergen.

Tundra climates ordinarily fit the Köppen climate classification ET, signifying a local climate in which at least one month has an average temperature high enough to melt snow (0 °C (32 °F)), but no month with an average temperature in excess of 10 °C (50 °F). The cold limit generally meets the EF climates of permanent ice and snows; the warm-summer limit generally corresponds with the poleward or altitudinal limit of trees, where they grade into the subarctic climates designated Dfd, Dwd and Dsd (extreme winters as in parts of Siberia), Dfc typical in Alaska, Canada, mountain areas of Scandinavia, European Russia, and Western Siberia (cold winters with months of freezing).

Despite the potential diversity of climates in the ET category involving precipitation, extreme temperatures, and relative wet and dry seasons, this category is rarely subdivided. Rainfall and snowfall are generally slight due to the low vapor pressure of water in the chilly atmosphere, but as a rule potential evapotranspiration is extremely low, allowing soggy terrain of swamps and bogs even in places that get precipitation typical of deserts of lower and middle latitudes. The amount of native tundra biomass depends more on the local temperature than the amount of precipitation.

Places featuring a tundra climate

Alpine tundra
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