Largely underlain by permafrost, much of the Arctic consists of the tundra – a biome1 characterised by low temperatures, a short growing season, low precipitation, and little tree growth. Containing less than 1 percent of the world’s flora, the tundra is home to low-growing plants with shallow roots such as shrubs, lichens, and mosses.
While the High Arctic tundra, i.e. lands above 75 degrees latitude, are largely devoid of vegetation, territories below the Arctic treeline – an ecological transition zone above which trees are incapable of growing – are much lusher. Even so, because of the harshness of its climate, the Arctic region has low plant diversity overall, despite its high floristic integrity (this means that plants found in any given part of the Arctic are usually found across the region as a whole).
Species richness, i.e. diversity, tends to increase as latitude decreases, whereas complexity of vegetation decreases as latitude increases. This extends beyond vegetation, affecting the food web as a whole due to the region’s extreme climatic conditions that are hard to adapt to. Plant and animal species living in the Arctic have learned to survive and reproduce in its unique environment, where temperatures can fall as low as -50° Celsius and extremes of solar radiation can plunge the sky into prolonged darkness (i.e. polar nights). Some species of animals have shown an exceptional capacity to adapt to the Arctic: great cormorants have been found to dive for fish daily and do so with great success even in the darkness of polar nights, while the Arctic ground squirrel was found to hibernate longer than any other mammal (for eight months) while relying both on its fat for energy and on supercooling to prevent body fluids from freezing. Reindeer, one of the Arctic’s main grazers, eat a variety of plant species in spring and summer and forage for lichens buried under snow when plants become rare in winter.
1 a region of the Earth's surface and the particular combination of weather conditions, plants, and animals that are found in it.
The Arctic is home to some of the world’s longest rivers, largest and deepest lakes, and other diverse freshwater ecosystems such as ponds, streams, wetlands, highlands, glaciers, etc., which can cover more than 80 percent of land in some parts of the Arctic. These bodies of water support a range of permanent and transitory organisms, from bacteria to large fish. Less than 1 percent of the world’s freshwater fish and anadromous fish (i.e. fish born in freshwater, but who live largely in saltwater, returning to freshwater only to spawn offspring) can be found in the freshwater systems of the Arctic.
With a total area of about 14 million square kilometres, the Arctic Ocean is the world’s smallest. Its perimeter is bordered by numerous seas, amongst them the Barents Sea, the Kara Sea, the Laptev Sea, the East Siberian Sea, the Chukchi Sea, the Beaufort Sea, and the Greenland Sea. The Arctic’s marine environment comprises diverse ecosystems, namely 17 out of the world’s 64 Large Marine Ecosystems (LMEs), some of which correspond to traditional Arctic seas or shelves. These LMEs can contain smaller domains that support higher levels of biodiversity due to their unique characteristics, one such example being the Pribilof Islands in the Bering Sea. The Arctic’s marine ecosystem has a wide breadth of living organisms – tens of thousands of species of microbes, over 2,000 species of algae, over 5,000 animal species, and many more – that too have adapted to the unique climatic conditions. The Arctic’s frozen water structure, from sea ice to iceberg to glaciers, are also habitats for a diversity of species.
Despite its particularities, the Arctic ecosystem is closely integrated with ecosystems across the world: Arctic animals – birds, fish, and even mammals – migrate to warmer southern regions in the winter, making the Arctic subject to high fluctuations in animal populations; the Arctic air carries cold air to the south in winter, while winds currents from the south carry warm air back to the Arctic; warm sea water cools as it is carried towards the Arctic by water currents, while cold fresh water from melting snow and ice crafts both sea conditions and climate on land through the thermohaline circulation system.
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