The sun does not rise at all in the northern reaches of the Arctic from mid-November to late January, contrasting with the almost constant sunlight received in the summer months (5). This dramatic variation in light levels means that the growing season for plants in the Arctic is highly variable, ranging from as little as 60 days, up to 200 days (6).
Despite the extreme conditions, many parts of this remarkable region support an array of plant life (5). In late winter and spring, ice algae blooms along the edge of the retreating sea ice, forming an important part of the Arctic marine ecosystem (1).
There are around 3,000 species of flowering plant found in the Arctic, including 96 rare, endemic species (1). Cottongrass grows in distinctive clumps, along with wildflowers such as moss campion (Silene acaulis), Arctic avens (Dryas integrifolia) and the rare Arctic poppy (Papaver laestadianum) (1) (5). The Arctic willow (Salix arctica) is one of the taller plants of the tundra, growing up to a couple of metres in height (5).
The diversity of mosses is high in the Arctic, with the 1,100 species of moss found in the region comprising 11 percent of the global number of known species (1).
Around 130 species of mammal inhabit the Arctic region, including the aptly named Arctic fox (Vulpes lagopus) and Arctic hare (Lepus arcticus), which are both superbly adapted for life at sub-zero temperatures, with their dense fur providing excellent insulation (7) (8). Herds of muskox (Ovibos moschatus) and reindeer (Rangifer tarandus) also roam the Arctic landscape. Undoubtedly, one of the most iconic mammals of the Arctic region is the polar bear (Ursus maritimus). At up to 2.6 metres long, this magnificent species is the world’s largest land carnivore (9).
The Arctic is also home to a number of marine-dwelling mammal species, including the main prey of the polar bear, the ringed seal (Pusa hispida) (10). The walrus (Odobenus rosmarus) with its enormous tusks, the mysterious narwhal (Monodon monoceros) and the snow-white beluga whale (Delphinapterus leucas) also inhabit the waters of the Arctic (3). Each of these species is equipped with a thick layer of fat to insulate them against the cold Arctic waters (3).
There are an estimated 280 species of bird that occur in the Arctic region (1). Some of these breed exclusively in the Arctic, including the brent goose (Branta bernicla), the ivory gull (Pagophila eburnea) and 17 of the 24 species of sandpiper (1) (11). Of the 206 shorebird species known worldwide, 69 of these occur in the Arctic, with many species undertaking long migrations to reach the region (1).
There are also predatory species of bird that inhabit the Arctic, including the snowy owl (Bubo scandiaca), which breeds and hunts on the Arctic tundra (12).
In spite of popular misconception, there are no species of penguin found in the Arctic, with these charismatic birds only occurring in the southern hemisphere (13).
Reptiles and amphibians
Due to the harsh conditions of the Arctic, reptiles and amphibians are generally poorly represented (1). Just four species of lizard occur in the Arctic region, with the viviparous lizard (Lacerta vivipara) being the most northerly occurring reptile species (1) (14).
Amphibians of the Arctic region include the Siberian salamander (Salamandrella keyserlingii), the Endangered Semirechensk salamander (Ranodon sibiricus) and the wood frog (Rana sylvatica) (1) (15).
Fish and invertebrates
There is no shortage of invertebrates in the Arctic, with an estimated 3,000 species of insect found in the region. By far the most common group of terrestrial invertebrates found there are in the Order Diptera, or flies (16). Many of the terrestrial species emerge only in the brief Arctic summer, remaining dormant for the rest of the year (16). The larvae of the Gynaephora groenlandica moth can take up to 14 years to mature, surviving the winter in a frozen state (16). Other invertebrates, such as mosquitoes, can complete their development in a single season (16).
In the Arctic Ocean, zooplankton, such as copepods, form an important part of the marine community (3). A number of species of krill also occur in the Arctic, and these provide a plentiful and important food source for fish, seabirds and whales (3).
In total, there are around 450 species of fish that live in the Arctic (1). The most northerly ranging of these is the Arctic charr (Salvelinus alpinus), which occurs in both the marine and freshwater systems of the Arctic (17). The Arctic cod (Boreogadus saida) forms vast shoals, and is specially adapted for a life in the icy waters by having proteins in its blood that act as antifreeze (1) (18).