Arctic ecology is the scientific study of the relationships between biotic and abiotic factors in the arctic, the region north of the Arctic Circle (66° 33'N). This region is characterized by two biomes: taiga (or boreal forest) and tundra. While the taiga has a more moderate climate and permits a diversity of both non-vascular and vascular plants, the tundra has a limited growing season and stressful growing conditions due to intense cold, low precipitation, and a lack of sunlight throughout the winter. Sensitive ecosystems exist throughout the Arctic region, which are being impacted dramatically by global warming.

The earliest hominid inhabitants of the Arctic were the Neanderthal sub-species. Since then, many indigenous populations have inhabited the region and continue to do so to this day.

The Arctic is a valued area for ecological research. During the Cold War, the Arctic became a place where the United States, Canada, and the Soviet Union performed significant research that has been essential to the study of climate change in recent years. A major reason why research in the Arctic is valuable for the study of climate change is that the effects of climate change will be felt more quickly and more drastically at higher latitudes of the world as above average temperatures are predicted for Northwest Canada and Alaska.Berkes, Fikret and Dyanna Jolly. "Adapting to Climate Change: Social- Ecological Resilience in a Canadian Western Arctic Community." Conservation Ecology 5 (2001). Accessed on February 23, 2014.Bocking, Stephen. "Science and Spaces in the Northern Environment." Environmental History 12 (2007): 867-94. Accessed on February 23, 2014.

Early human history and ecology in the Arctic Current evidence of woolly mammoth death due to hunting dates hominid presence in the Arctic to as early as 45,000 years ago, while other evidence has indicated hominid presence near the Arctic Circle at an even earlier time period. It has been speculated that the hunting abilities and advanced tools of these early populations could have contributed to their ability to become established in the Arctic. A subject of debate in current Arctic ecological research is whether these Arctic inhabitants belonged to the species Homo neanderthalensis, or whether they were early members of the species Homo sapiens sapiens, or modern-day humans. This debate stems from a current lack of knowledge of the processes which led to the replacement of Neanderthal populations by Homo sapiens sapiens, but there is agreement that evidence of tool-use and hunting in the Arctic suggests some form of hominid presence in this region.

About 40,000 years ago, Neanderthals were globally replaced by modern humans, Homo sapiens sapiens.

There has been evidence found of the presence of populations Homo sapiens sapiens that utilized "leaf point" tools in the Arctic region of Siberia as early as 13,000 years ago. Paleo-arctic populations of Homo sapiens sapiens occupied northern Alaska between 13,000 and 8,000 years ago, during the transition between the Pleistocene era and the Holocene era. Research has inferred from the discovery of alternate types of tool technology in the Arctic dated to a similar period that these populations "supplant[ed], amalgamat[ed] with, or acculturat[ed]" the peoples of the "northern Cordilleran tradition".

Consideration of known historical environmental change and dates of human presence has indicated a potential link between the prey population cycles caused by environmental disturbance and Paleo-arctic residence in Arctic habitats. Mann et al. suggest that the resulting dependence of Paleo-arctic hunters on disturbance, along with the spreading of inhospitable habitats (tussock-tundra) and pests such as mosquitoes, could have resulted in the decrease of Paleo-arctic populations in Arctic regions following the end of the Pleistocene. There is still uncertainty related to determining the presence or absence of specific Arctic groups during this period.

Paleo-Eskimos followed the Paleo-arctic populations between 5,000 and 6,000 years ago, and research has suggested that they were a more widespread and lingering population with an ancestral relationship to modern-day indigenous Arctic inhabitants. Genetic evidence has given rise to the theory that the Paleo-Eskimos were a singular people which resided in Alaska, Canada, and Greenland and subsisted by hunting large terrestrial mammals and seals. Research also suggests shared genetic and cultural ancestry between this group and more Southern indigenous peoples.

Dating back to a similar time period as the Paleo-Eskimos, evidence has been found of the Arctic Small Tool tradition (ASTt) culture. This culture is a conceptual linkage between the similar tool-usage of multiple Arctic cultures, including Saqqaq and Pre-Dorset peoples. The Arctic Small Tool tradition was directly ancestral to the Dorset culture, which occupied the North American Arctic from 2700 to 1200 years ago.

The migration of the early Inuit (Thule) peoples to the Arctic replaced Paleo-Eskimo populations from 700 to 800 years ago. The use of the term 'Thule' to describe these peoples has been debated due to its "unrelated" use by the Nazi party. The Thule peoples likely descended from Arctic Small Tool tradition and Dorset populations and are known to have given rise modern-day Inuit, one indigenous group currently residing in the North-American Arctic. According to a University of Lapland publication, the Inuit are one of "over 40 different ethnic groups living in the Arctic".

The rapid cooling the earliest inhabitants felt signaled an early onset of the Little Ice Age of the 1300s. This caused the sea ice to expand, which made traveling through Greenland and Iceland impossible to manage, trapped the people in their homes and settlements, and caused trade come to a stop.

In the late eighteenth and early nineteenth centuries, as European trade interests among the North West Company and the Hudson's Bay Company expanded into northern Canada, Arctic indigenous peoples began to become more involved in the trade process. Increasing numbers of European goods, including kettles, iron tools, tobacco, alcohol, and guns, were bought and traded by the indigenous peoples within their communities. Indigenous societies in the early eighteenth century also began to buy guns from European traders; these guns increased hunting efficiency and led to a scarcity of resources in the region, a version of what American human ecologist Garrett Hardin called "the tragedy of the commons."Wynn, Graeme. Canada and Arctic North America: An Environmental History. Santa Barbara, Calif.: ABC-CLIO, 2007. pgs. 64-72.

The lifestyles of indigenous Arctic populations reflect simultaneously spiritual and scientific understandings of their environments.UNESCO. Climate Change and Arctic Sustainable Development: scientific, social, cultural and educational challenges. Paris: UNESCO, 2009. pgs. 73-75.

Arctic environment Both the terrestrial and oceanic aspects of the Arctic region influence Arctic ecology. Two influential environmental factors are sea ice and permafrost.

Sea ice is frozen seawater that moves with oceanic currents. It is a common habitat and resting place for animals, particularly during the winter months. Over time, small pockets of seawater get trapped in the ice, and the salt is squeezed out. This causes the ice to become progressively less salty. Sea ice persists throughout the year, but there is less ice available during summer months.

Large portions of the land are also frozen during the year. Permafrost is substrate that has been frozen for a minimum of 2 years. There are two types of permafrost: discontinuous and continuous. Discontinuous permafrost is found in areas where the mean annual air temperature is only slightly below freezing (); this forms in sheltered locations. In areas where the mean annual soil surface temperature is below , continuous permafrost forms. This is not limited to sheltered areas and ranges from a few inches below the surface to over deep. The top layer is called the active layer. It thaws in the summer and is critical to plant life.

Biomes Moisture and temperature are major physical drivers of natural ecosystems. The more arid and colder conditions found at higher northern latitudes (and high elevations elsewhere) support tundra and boreal forests. The water in this region is generally frozen and evaporation rates are very low. Species diversity, nutrient availability, precipitation, and average temperatures increase as the landscape progresses from the tundra to boreal forests and then to deciduous temperate ecosystems, which are found south of the Arctic biomes.

Tundra

Tundra is found north of 70° N latitude in North America, Eurasia and Greenland. It can be found at lower latitudes at high elevations as well. The average temperature is ; during the summer it is less than . Average precipitation ranges from , and the permafrost can be "several hundred meters" thick. Plant species supported by tundra are generally short, lacking stems due to threats posed to vascular structure by frozen temperatures, and much of their growing matter is found below the soil. They are composed mainly of perennial forbs, dwarf shrubs, grasses, lichens, and mosses.Alaska Department of Fish and Game. 2006. Our Wealth Maintained: A Strategy for Conserving Alaska's Diverse Wildlife and Fish Resources. Alaska Department of Fish and Game, Juneau, Alaska. xviii+824 p.

Boreal

Compared to the tundra, boreal forest has a longer and warmer growing season and supports increased species diversity, canopy height, vegetation density, and biomass. Unlike the tundra, which is characterized by a lack of trees and tall vegetation, boreal forests support a number of different tree species. Boreal conditions can be found across northern North America, Europe and Eurasia. The boreal forests in the interior of the continents grow on top of permafrost due to very cold winters (see drunken trees), though much of the boreal forest biome has patchy permafrost or lacks permafrost completely. The short (3–4 month) growing season in boreal forests is sustained by greater levels of rainfall than the tundra receives (between per year). This biome is dominated by closed canopy forests of evergreen conifers, especially spruces, fir, pine and tamarack with some diffuse-porous hardwoods. Shrubs, herbs, ferns, mosses, and lichens are also important species. Stand-replacing crown fires have been indicated to be important to this biome, though other research suggests that stand-replacing crown fires may be more harmful to forest biodiversity than ground fires. Recent research demonstrates that alterations in the frequency of fires and droughts in this region due to climate change may be potentially damaging to biodiversity.

Sea ice

Adaptations to conditions

Humans Humans living in the Arctic region rely on acclimatization along with physical, metabolic, and behavioral adaptations to tolerate the extreme cold in the Arctic. There is evidence that modern Inuit populations have a high prevalence of specific genes that code for fat to aid in thermal regulation and that Arctic indigenous populations have significantly higher basal metabolic rates (BMRs) than non-indigenous populations. BMR is defined as "the rate of oxygen uptake at rest in the fasting and thermo-neutral state" by W.P.T. James. Research by Keestra et al. has also suggested a link between adaptations to cold climates and mitochondrial responses to thyroid hormones which "enhance" "metabolic heat production".

Other animals