The vast arctic tundra is a circumpolar region in the far Northern Hemisphere, north of the boreal forest belt. It is here defined as comprising parts of northern coastal Scandinavia, northern coastal Russia, northern coastal Alaska, the Canadian High Arctic, and the islands of Greenland and Iceland. The word ‘tundra’ usually refers only to areas where the subsoil is permanently frozen (‘permafrost’). The lands within this region are typified by cold winters and cool summers, low precipitation, and an absence of trees. Biodiversity in the tundra is low, with the few plants and animals that manage to survive there being adapted to short growing seasons with long periods of sunlight, as well as to extreme cold, dark, snow and ice-covered winter conditions. Today they are essentially climax communities, with lichens serving as a basis for the existence of the large herds of reindeer or caribou (Rangifer tarandus), which in their turn are the staple winter food of the grey wolf (Canis lupus).
Species and subspecies
During prehistoric times the muskox (Ovibos moschatus) occurred throughout the Siberian and North American Arctic from the Urals east to Greenland and south as far as the ice sheets extended. It appears to have died out in Europe around 9000 years ago, and in Siberia around 2000 years ago. In the nineteenth century it was still to be found from Point Barrow, Alaska east across Canada to north-eastern Greenland and south to north-eastern Manitoba. By the early twentieth century it had been wiped out in Alaska by excessive hunting, but has made a considerable recovery in other areas. In the Canadian arctic they now inhabit most large islands (with the exception of Baffin Island) and the mainland tundra of the Northwest Territories and Nunavut from the coast of Hudson Bay west to almost the Mackenzie River, south to the tree line. They still occur naturally over the entire north of Greenland, in addition to several introduced populations further south. The species has also been reintroduced to parts of Alaska (beginning with Nunivak Island as early as 1935), Norway, and the Taimyr Peninsula and Wrangel Island in Russia. Taken together the species appears to be safe.
The reindeer (Rangifer tarandus), also known as the caribou in North America, is a type of deer found, as a species, both in the northernmost regions of North America and Greenland as well as in northern Eurasia. Despite this wide range many subspecies are threatened, and a few have already gone extinct. The Barren Ground caribou (R. t. groenlandicus) is found in the Canadian High Arctic islands (Nunavut and Northwest Territories) and western Greenland. The Peary caribou (R. t. pearyi) is found in the Canadian High Arctic islands (Nunavut and Northwest Territories). The Labrador caribou (R. t. caboti) occurs in the tundra regions of Quebec and Labrador. The Porcupine caribou (R. t. granti), so-named for the Porcupine River which runs through much of its range, lives in northern Alaska and adjacent north-western Canada (Yukon). The single herd of around 200,000 animals migrates some 2400 km each year between their winter range and their calving grounds near the Beaufort Sea, the longest land migration route of any mammal. It is highly vulnerable to climatic factors, and the population fluctuates greatly as a result. The Siberian tundra reindeer (R. t. sibiricus) is still found across much of northern Eurasia, but has been supplanted almost everywhere by domesticated reindeer. The largest remaining population of wild reindeer in the Old World lives in the Pyasina River drainage on the Taimyr Peninsula in northcentral Siberia, where the number of individuals exceeds 100,000 as a result of partial protection.
The snowy owl (Bubo scandiacus) still has a considerable range across predominantly open tundra regions from western Scandinavia through northern Russia to Alaska, northern Canada, and Greenland. It has also bred occasionally in Iceland and in the United Kingdom. During the winter the birds move further south into the mainland United States, northern Europe, and northern Asia. The species appears to be undergoing a considerable decline in population, however, and is now thought to number less than 30,000.
The Siberian crane (Leucogeranus leucogeranus) is a large and spectacular snow-white species historically spread over an immense area from the Ural River in the south-east to the coast of the Arctic Ocean in north-eastern Siberia, where it favours bogs in conifer forests and steppes. Although long protected by law over most of its range, it was much persecuted and disturbed by hunters over its long migration routes and, like the more famous whooping crane (Grus americana) of North America, had difficulty maintaining its numbers. By the mid-twentieth century it was already reduced to two widely separated groups, known as the Eastern Flyway and Western/Central Flyway populations. The vast majority, the Eastern Flyway population, breed in the Yakutia region of northeastern Arctic Russia between the Kolyma and Yana rivers and south to the Morma Mountains. Younger, non-breeding birds summer in Dauria on the border between Russia, Mongolia, and China, and occasionally in central Mongolia as well. The main wintering sites were formerly in the middle to lower reaches of the Yangtze River, although today almost all winter at or near Lake Poyang in China. The birds rely on a network of important wetlands along their migration route, which follows the Yana, Indigirka, and Kolyma rivers before continuing along the Aldan River and its tributaries and south into China. The other, remnant population of Siberian cranes (less than 20 birds) breeds in West Siberia and is divided into two further subpopulations, the Western Asian Flyway and Central Asian Flyway flocks. The Central Asian flock breeds in the Kunovat River drainage in Russia, and historically wintered in Keladeo National Park, north-western India. None have been seen at Keoladeo since the early 2000s, although unconfirmed but credible reports of passing birds continue from Russia, Uzbekistan, Kazakhstan, Pakistan, and India. The Western Asian flock breeds in the Konda and Alymka river drainages of West Siberia, and winters in Fereydoonkenar in Iran. It uses the Volga River delta as a migration stopover, and passes over Azerbaijan during its migration. Captive-breeding and reintroduction efforts have recently begun in Iran. Currently, the total population for the species as a whole is about 3750, up from less than 2000 in 1965.
The red-breasted goose (Branta ruficollis) breeds on the Taimyr, Gydan, and Yamal peninsulas of north-central Russia. Prior to the 1950s much of the population wintered along the western coast of the Caspian Sea, primarily in Azerbaijan, and in Iran and Iraq, although the wintering grounds thereafter rapidly shifted to the western Black Sea coast. The total number is small and prone to dramatic fluctuations for reasons that are not fully understood.
The lesser white-fronted goose (Anser erythropus) historically bred across much of subarctic Eurasia but is now confined to four main areas of northern Scandinavia and the northern coast of Siberia, from where it migrates in winter to Europe, the Middle East, and southern Asia. It has undergone a significant decline due to by-catch mortality in gillnets, oil pollution, disease, and hunting.
The long-tailed duck (Clangula hyemalis) has a circumpolar distribution, breeding along the arctic coasts of North America, Greenland, Iceland, Europe, and Asia, from where it winters in the north-eastern United States, north-western Europe, and in central and western coastal Asia. It is threatened by hunting, fisheries by-catch, pollution, and disease.
Steller’s eider (Polysticta stelleri) is a small sea duck that breeds patchily along the northern coasts of Siberia and Alaska, from where it winters in Novaya Zemlya, Norway, south-western Alaska, and northern Japan. It has undergone a significant decline, particularly in Alaska, due to hunting, habitat destruction, and possibly the effects of climate change.
The Eskimo curlew (Numenius borealis) was historically abundant in its breeding grounds on the barren tundra of Canada north of the Arctic Circle, roughly between the Bathurst Peninsula and Point Lake and perhaps extending into Alaska. It migrated southward across Hudson Bay to Labrador and New England, whence it started its non-stop flight over the Atlantic Ocean and the Caribbean Sea to winter in southernmost South America. The spring flight followed a more westerly route, because there are records indicating a flyway passing over Yucatán, Texas, and west of the Great Lakes to north-western Canada. Hence, it flew twice a year across both Americas. Excessive shooting during the migration in eastern Canada and New England is thought to account for the tragic decline of this species. In 1863 over 7000 birds were killed in one day on Nantucket Island. As late as the period between 1856 and 1875 immense flocks used to rest in Texas, but by 1905 only three birds were seen there. Hecatombs of these curlews were shot as they migrated across the United States. Hunters sent wagonloads of birds back from the shooting grounds. They were very easy to kill, because they fed close together and were trustful of humans. In 1929 A. C. Bent, in his Life Histories of North American Shore Birds, declared of the curlew: ‘It is now but a memory of the past.’ However, in 1932 an individual was taken in Newfoundland, and a week later four were seen on Long Island. It was last confirmed from its wintering grounds in South America in 1939. Sporadic sight records followed elsewhere at long intervals: 1945, 1946, 1950, 1959, 1960, 1962, 1963, and 1970 on the coast of Texas and Louisiana as well as on the Atlantic coast. Some of these are doubtful, but in 1963 one bird was shot with certainty in Barbados. While there have been several unconfirmed reports in the decades since, with the latest alleged sighting occurring in Barbados as recently as 2012, the species is now almost certainly extinct.
A related species, the bristle-thighed curlew (N. tahitiensis), breeds in the tundra on the lower Yukon River and the central Seward Peninsula of western Alaska, wintering on various islands in the South Pacific. The total population is estimated at around 10,000.
Two migratory wading birds of the genus Calidris are threatened by coastal development in their wintering grounds. The spoon-billed sandpiper (C. pygmaea) breeds in northeastern Russia and winters in South East Asia, where it has declined dramatically since the 1970s. The current total population is believed to be around 500. The great knot (C. tenuirostris) breeds in north-eastern Siberia and winters mainly in Australia, but also patchily throughout the coastal areas of South and South East Asia and the Arabian Peninsula.