High Arctic Tundra

• Category: Grassland, Tundra, and Human Biomes.
• Geographic Location: Arctic.
• Summary: At the top of the world rests the high-Arctic tundra. This fortress of snow and ice is home to only the most resilient species.

The high-Arctic tundra is the northernmost terrain in the world. It is characterized by a harsh polar climate, permafrost, and little vegetation, but is home to an array of herbivores, carnivores, and migratory birds. Moss and lichen speckle the desolate landscape, where snowy owls and polar bears roam. Long winters and fleeting summers mark the year. Much of this ecosystem is being lost, however. Global climate change is altering the Arctic, and its species are faced with the loss of their homes and their lives. The high Arctic is not a contiguous land mass; rather, it is composed of islands with similar environmental and biological features. All lands above the 75-degrees north latitude line are high-Arctic tundra, symbolized by places like Spitsbergen, situated in the Arctic Ocean between Norway and the North Pole, and a few southward locations, such as the Canadian Prince of Wales Island.

These northernmost places are not only characteristically cold but also have an extraordinarily dry climate. Interestingly, the high Arctic has as little precipitation as the Sonoran and Chihuahuan deserts. Due to this dry climate and lack of vegetation, much of the high-Arctic tundra can technically be considered a polar desert. As such, the zone experiences large swings in temperature. The winters are long and devoid of sun, in contrast to the conspicuously short summers with continuous daylight. The temperature can remain below 32 degrees F (0 degrees C) for 9 months, and the freeze subsides only for two to eight weeks in the summer. Unlike temperate ecoregions, the high-Arctic tundra does not have a spring or autumn. Instead, the transition from summer to winter is punctuated by the freezing of ice on coastal shores. Likewise, the period between winter and summer is aptly named “the thaw” to portray the ice retreat.

Flora and Fauna

The austere environment dictates which organisms can survive: only the hardiest plants and animals. The flora and fauna of the high-Arctic tundra differ considerably from that of its southern counterparts. There are no trees and relatively few plants; those plants that have adapted to this environment generally are no more than a few centimeters tall. There is little plant diversity. Patches of cushion plants, sedges, grasses, moss, and lichen are interlaced among large areas with little to no flora. Vegetative areas are dominated by moss and lichen, with the former thriving in moist settings and the latter being the only vegetation in dry tracts of land.

One condition limiting which plants survive in the Arctic is the ever-present frozen ground: permafrost. The permafrost can reach its deepest extent, as much as 984 feet (300 meters) thick in the high-Arctic tundra; it also contains massive pieces of ice here. A slice of the top layer melts in the summer, allowing phototrophic plants to establish shallow roots while taking advantage of the perpetual summer sunlight. The surge of new greenery during the summer growing season is the sustenance for herbivore populations. Herbivores residing in the high tundra include lemmings, Arctic hare, caribou, and musk oxen. These land mammals must deal with two unique situations: their food sources are available only during the summer, and they must cope with temperatures as low as minus 58 degrees F (minus 50 degrees C) in winter.

None of the high-Arctic herbivores hibernate. They have behavioral, physiological, and physical adaptations that allow them to handle severe conditions. One common physiological adaptation is the storage of brown fat. This type of fat is the metabolic equivalent of a furnace, so energy-rich that it generates sufficient heat to keep the animal warm in the harshest external conditions. In addition to brown fat, many Arctic mammals use snow for warmth. Temperatures under the snow are much higher than those in the open air, and resourceful Arctic residents take advantage of this fact. Lemmings, for example, use snow to insulate their underground burrows and shelter themselves from icy winds.

In addition to the mammalian herbivores, the tundra is home to several carnivores, including polar bears, Arctic foxes, and wolverines. Polar bears are unique cases because they don't spend much time on land. They occupy much of the winter hunting seals while wandering atop the ice covering the Arctic Ocean. When the ice melts in the summer, they move onto land, where they forage berries. In addition to taking advantage of the bountiful summer plant life, pregnant females den on land to hibernate and give birth.

Like the polar bear, the Arctic fox is a definitive Arctic species. The primary prey of these foxes are lemmings; they also scavenge marine-mammal carrion and actively hunt Arctic hares and ptarmigans.

The avian inhabitants of the high-Arctic tundra are adorned with snowy-white plumage. They include the snowy owl; rock ptarmigan; snow goose; snow bunting; and the largest falcon in the world, the gyrfalcon. Some of these birds are year-round residents; others call the Arctic their summer home. Like all high-Arctic fauna, the birds have notably differentiated characteristics. Ptarmigan, for example, grow feathers on the soles of their feet and their toes. These feathers effectively act as snowshoes and allow them to scamper upon deep snowdrifts. How much longer deep winter snowdrifts will occur in the Arctic is an open question, however.

Climate Change

Arctic snows are melting earlier each year, and the accumulation of snow is delayed by increasingly late freezes. Global climate change is taking a great toll on the Arctic; the fragility of this wilderness is a glaring issue that has sparked international concern. The seriousness of the threat of climate change was exemplified by the 2008 listing of polar bears as a threatened species. The reduction of snow cover, sea ice extent, and ice thickness, along with the melting of glaciers and permafrost, are leading to the degradation of the Arctic ecosystem. The warming temperatures increase the melting of permafrost, which in turn increases the release of methane. The higher temperatures of the region and less harsh environment have also brought about the growth of shrubs and other foreign flora. These invasive shrubs threaten lichen growth by crowding lichen out, which threatens the stability of animals that depend on lichen. Only time will tell whether the Arctic of the future bears in-depth resemblance to the ecosystem we know today.

Bibliography

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Hobbie, John E., et al. "Ecosystem Responses to Climate Change at a Low Arctic and a High Arctic Long-Term Research Site." Ambio, vol. 46, 2017, pp. 160-73.

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