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Beringia is defined today as the land and maritime area bounded on the west by the in ; on the east by the in ; on the north by 72 degrees north latitude in the ; and on the south by the tip of the Kamchatka Peninsula. It includes the , the , the , the Chukchi and Kamchatka Peninsulas in as well as in the .

The area includes land lying on the North American Plate and Siberian land east of the . Historically, it formed a that was up to wide at its greatest extent and which covered an area as large as and together, totaling approximately . Today, the only land that is visible from the central part of the Bering land bridge are the , the of St. Paul and St. George, St. Lawrence Island, and King Island.

The term Beringia was coined by the Swedish botanist Eric Hultén in 1937.

(2007). 9780231130608, I have no energy Columbia University Press. .
During the ice ages, Beringia, like most of and all of and , was not because .
(1973). 9789004035515, Brill Archive. .
It was a grassland , including the land bridge, that stretched for hundreds of kilometres into the continents on either side.

It is believed that a small human population of at most a few thousand arrived in Beringia from eastern Siberia during the Last Glacial Maximum before expanding into the settlement of the Americas sometime after 16,500 years . This would have occurred as the American glaciers blocking the way southward melted, but before the bridge was covered by the sea about 11,000 years BP.

Before European colonization, Beringia was inhabited by the on both sides of the straits. This culture remains in the region today along with others. In 2012, the governments of Russia and the United States announced a plan to formally establish "a transboundary area of shared Beringian heritage". Among other things this agreement would establish close ties between the Bering Land Bridge National Preserve and the Cape Krusenstern National Monument in the United States and Beringia National Park in Russia.


Geography
The remains of mammals that had been discovered on the and islands in the at the close of the nineteenth century indicated that a past land connection might lie beneath the shallow waters between and Chukotka. The underlying mechanism was first thought to be tectonics, but by 1930 changes in the icemass balance, leading to global sea-level fluctuations, were viewed as the cause of the Bering Land Bridge.Hopkins DM. 1967. Introduction. In: Hopkins DM, editor. The Bering land bridge. Stanford: Stanford University Press. pp. 1–6. In 1937, Eric Hultén proposed that around the Aleutians and the Bering Strait region were tundra plants that had originally dispersed from a now-submerged plain between Alaska and Chukotka, which he named Beringia after who had sailed into the strait in 1728.Hultén E. 1937. Outline of the history of arctic and boreal biota during the Quaternary Period. New York: Lehre J. Cramer. The American arctic geologist David Hopkins redefined Beringia to include portions of Alaska and Northeast Asia. Beringia was later regarded as extending from the Verkhoyansk Mountains in the west to the in the east. The distribution of plants in the genera and are good examples of this, as very similar genera members are found in Asia and the Americas.

During the Pleistocene epoch, global cooling led periodically to the expansion of glaciers and lowering of sea levels. This created land connections in various regions around the globe.[Lowe JJ, Walker M. 1997 Reconstructing quaternary environments, 2nd edn. Harlow, UK: Prentice Hall. Today, the average water depth of the Bering Strait is , therefore the land bridge opened when the sea level dropped more than below the current level. A reconstruction of the sea-level history of the region indicated that a seaway existed from  BP, a land bridge from  BP, intermittent connection from  BP, a land bridge from  BP, followed by a Holocene sea-level rise that reopened the strait. Post-glacial rebound has continued to raise some sections of coast.

During the last glacial period, enough of the earth's water became frozen in the great covering and to cause a drop in . For thousands of years the sea floors of many shallow seas were exposed, including those of the , the to the north, and the to the south. Other around the world have emerged and disappeared in the same way. Around 14,000 years ago, mainland was linked to both and , the became an extension of continental via the dry beds of the and , and the dry bed of the South China Sea linked , , and to .


Beringian refugium
The last glacial period, commonly referred to as the "Ice Age", spanned 125,000–14,500 and was the most recent within the current ice age, which occurred during the last years of the Pleistocene era. The Ice Age reached its peak during the Last Glacial Maximum, when began advancing from 33,000YBP and reached their maximum limits 26,500YBP. Deglaciation commenced in the Northern Hemisphere approximately 19,000YBP and in Antarctica approximately 14,500 yearsYBP, which is consistent with evidence that glacial meltwater was the primary source for an abrupt rise in sea level 14,500YBP and the bridge was finally inundated around 11,000 YBP. The fossil evidence from many continents points to the extinction of large animals, termed Pleistocene megafauna, near the end of the last glaciation.

During the Ice Age a vast, cold and dry stretched from the arctic islands southwards to China, and from Spain eastwards across Eurasia and over the Bering land bridge into Alaska and the Yukon where it was blocked by the Wisconsin glaciation. The land bridge existed because sea-levels were lower because more of the planet's water than today was locked up in glaciers. Therefore, the flora and fauna of Beringia were more related to those of Eurasia rather than North America. Beringia received more moisture and intermittent maritime cloud cover from the north Pacific Ocean than the rest of the Mammoth steppe, including the dry environments on either side of it. This moisture supported a shrub-tundra habitat that provided an ecological refugium for plants and animals. In East Beringia 35,000 YBP, the northern arctic areas experienced temperatures 1.5 C degrees warmer than today but the southern sub-Arctic regions were 2 C degrees cooler. During the LGM 22,000 YBP the average summer temperature was 3–5 C degrees cooler than today, with variations of 2.9 C degrees cooler on the to 7.5 C cooler in the Yukon. In the driest and coldest periods of the Late Pleistocene, and possibly during the entire Pleistocene, moisture occurred along a north-south gradient with the south receiving the most cloud cover and moisture due to the air-flow from the North Pacific.

In the Late Pleistocene, Beringia was a mosaic of biological communities.Hoffecker JF, Elias SA. 2007 Human ecology of Beringia. New York, NY: Columbia University Press.Elias SA, Crocker B. 2008 The Bering land bridge: a moisture barrier to the dispersal of steppe-tundra biota? Q. Sci. Rev. 27, 2473–2483Brigham-Grette J, Lozhkin AV, Anderson PM, Glushkova OY. 2004 Paleoenvironmental conditions in Western Beringia before and during the Last Glacial Maximim. In Entering America, northeast Asia and Beringia before the last glacial maximum (ed. Madsen DB), pp. 29–61. Salt Lake City, UT: University of Utah Press Commencing from  BP (MIS 3), steppe–tundra vegetation dominated large parts of Beringia with a rich diversity of grasses and herbs.Sher AV, Kuzmina SA, Kuznetsova TV, Sulerzhitsky LD . 2005 New insights into the Weichselian environment and climate of the East Siberian Arctic, derived from fossil insects, plants, and mammals. Q. Sci. Rev. 24, 533–569. There were patches of shrub tundra with isolated refugia of ( Larix) and ( Picea) forests with ( Betula) and ( Alnus) trees.Anderson PH, Lozhkin AV. 2001 The Stage 3 interstadial complex (Karginskii/middle Wisconsinan interval) of Beringia: variations in paleoenvironments and implications for paleoclimatic interpretations. Q. Sci. Rev. 20, 93–125 It has been proposed that the largest and most diverse megafaunal community residing in Beringia at this time could only have been sustained in a highly diverse and productive environment.Guthrie RD. 1982 Mammals of the mammoth steppe as paleoenvironmental indicators. In Paleoecology of Beringia (eds Hopkins DM, Matthews JV, Schweger CE, Young SB), pp. 307–324. New York, NY: Academic Press Analysis at Chukotka on the Siberian edge of the land bridge indicated that from  BP (MIS 3 to MIS 2) the environment was wetter and colder than the steppe–tundra to the east and west, with warming in parts of Beringia from  BP.Kuzmina SA, Sher AV, Edwards ME, Haile J, Yan EV, Kotov AV, Willerslev E. 2011 The late Pleistocene environment of the Eastern West Beringia based on the principal section at the Main River, Chukotka. Q. Sci. Rev. 30, 2091–2106 These changes provided the most likely explanation for mammal migrations after  BP, as the warming provided increased forage for browsers and mixed feeders. Beringia did not block the movement of most dry steppe-adapted large species such as saiga antelope, woolly mammoth, and caballid horses. However, from the west the went no further east than the , and from the east North American camels, the American -like equids, the short-faced bear, bonnet-headed muskoxen, and did not travel west. At the beginning of the Holocene, some -adapted species left the refugium and spread westward into what had become tundra-vegetated northern Asia and eastward into northern North America.

The latest emergence of the land bridge was years ago. However, from  BP the Laurentide ice sheet fused with the Cordilleran ice sheet, which blocked gene flow between Beringia (and Eurasia) and continental North America.Gowan, E.J. (2013) An assessment of the minimum timing of ice free conditions of the western Laurentide ice sheet. Quaternary Science Review, 75, 100–113. The Yukon corridor opened between the receding ice sheets  BP, and this once again allowed gene flow between Eurasia and continental North America until the land bridge was finally closed by rising sea levels  BP. During the Holocene, many mesic-adapted species left the refugium and spread eastward and westward, while at the same time the forest-adapted species spread with the forests up from the south. The arid adapted species were reduced to minor habitats or became extinct.

Beringia constantly transformed its as the changing climate affected the environment, determining which plants and animals were able to survive. The land mass could be a barrier as well as a bridge: during colder periods, glaciers advanced and precipitation levels dropped. During warmer intervals, clouds, rain and snow altered and drainage patterns. remains show that , and once grew beyond their northernmost range today, indicating that there were periods when the climate was warmer and wetter. The environmental conditions were not homogenous in Beringia. Recent studies of bone demonstrate that western Beringia () was colder and drier than eastern Beringia ( and ), which was more ecologically diverse. , which depended on shrubs for food, were uncommon in the open dry landscape characteristic of Beringia during the colder periods. In this tundra, flourished instead.

The extinct pine species has been described from Pliocene sediments in the Yukon areas of the refugium.

The paleo-environment changed across time. Below is a gallery of some of the plants that inhabited eastern Beringia before the beginning of the .

File:ArtemisiaVulgaris.jpg|Artemisia File:Carex halleriana.jpg| () File:Grassflowers.jpg| () File:Salix-lanata-total.JPG| ()


Human habitation
The Bering land bridge is a postulated route of to the Americas from Asia about 20,000 years ago. An open corridor through the ice-covered North American Arctic was too barren to support human migrations before around 12,600 BP. Humans may have taken different path into Americas than thought Arctic passage wouldn't have provided enough food for the earliest Americans' journey by Thomas Summer, published in "Science News" on August 10, 2016 A study has indicated that the genetic imprints of only 70 of all the individuals who settled and traveled the land bridge into North America are visible in modern descendants. This genetic bottleneck finding is an example of the and does not imply that only 70 individuals crossed into North America at the time; rather, the genetic material of these individuals became amplified in North America following isolation from other Asian populations.

Seagoing coastal settlers may also have crossed much earlier, but there is no scientific consensus on this point, and the coastal sites that would offer further information now lie submerged in up to a hundred metres of water offshore. Land animals migrated through Beringia as well, introducing to species that had evolved in Asia, like such as and , which into now-extinct North American species. Meanwhile, and that had evolved in North America (and later became extinct there) migrated into Asia as well at this time.

A 2007 analysis of mtDNA found evidence that a human population lived in genetic isolation on the exposed Beringian landmass during the Last Glacial Maximum for approximately 5,000 years. This population is often referred to as the Beringian Standstill population. A number of other studies, relying on more extensive genomic data, have come to the same conclusion. Genetic and linguistic data demonstrate that at the end of the Last Glacial Maximum, as sea levels rose, some members of the Beringian Standstill Population migrated back into eastern Asia while others migrated into the Western Hemisphere, where they became the ancestors of the indigenous people of the Western Hemisphere. Environmental selection on this Beringian Standstilll Population has been suggested for genetic variation in the Fatty Acid Desaturase gene cluster and the ectodysplasin A receptor gene.


Previous connections
evidence demonstrates previous connections between North America and Asia. Similar fossils occur both in and in . For instance the dinosaur was found in both Mongolia and western North America. Relatives of , , and even rex all came from Asia.

Fossils in demonstrate a diffusion of Asian mammals into North America around 55 million years ago. By 20 million years ago, evidence in North America shows a further interchange of mammalian species. Some, like the ancient saber-toothed cats, have a recurring geographical range: Europe, Africa, Asia, and North America. The only way they could reach the was by the Bering land bridge. Had this bridge not existed at that time, the fauna of the world would be very different.


See also
  • Ancient Beringian
  • Bering Strait crossing
  • Little John (archeological site)
  • Geologic time scale
  • Last glacial period
  • Yukon Beringia Interpretive Centre


Further reading
  • (2018). 9780231130608, Columbia University Press. .
  • Pielou, E. C., After the Ice Age: The Return of Life to Glaciated North America (Chicago: University of Chicago Press) 1992


External links

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