The arctic tundra is a vast, treeless biome located in the high latitudes of the Northern Hemisphere. This landscape is defined by its exceptionally cold and harsh environment and is shaped by frost-molding processes. The region’s conditions place extreme constraints on the life that can survive there.
Geographic Location and Climate
The arctic tundra forms a continuous, circumpolar belt across the northern reaches of the globe. It stretches across northern North America, including Alaska and Canada, and extends through the coastal regions of Greenland, northern Scandinavia, and Siberia in Russia. This biome is situated north of the taiga, or boreal forest, and south of the permanent polar ice caps, creating a transitional zone between these two major ecosystems.
The climate is characterized by long, intensely cold winters and short, cool summers. Winter temperatures average around -34° C (-30° F), while summer temperatures are milder, ranging from 3° to 12° C (37° to 54° F). These cool summer temperatures are just enough to thaw the very surface of the soil. Despite the presence of water from melted snow and ice, the tundra is considered a cold desert because its annual precipitation is very low, between 15 to 25 centimeters (6 to 10 inches), mostly falling as snow.
These climatic conditions result in a brief growing season of only 50 to 60 days, the only time when vegetation can actively grow and reproduce. The sun can remain below the horizon for weeks during the winter, and in the summer, it can be present for 24 hours a day, providing continuous but low-angle sunlight.
The Role of Permafrost
A defining feature of the arctic tundra is the presence of permafrost, a thick layer of soil, gravel, and finer materials that remains frozen year-round. This permanently frozen ground can extend hundreds of meters deep, acting as an impermeable barrier beneath the surface. Permafrost dictates much of the tundra’s physical and biological characteristics. It is a relic of the last ice age.
Above the permafrost lies the active layer, a thin stratum of soil that thaws during the brief summer and refreezes in the winter. Because the underlying permafrost prevents water from draining away, the thawed active layer becomes saturated. This poor drainage creates a waterlogged landscape dotted with numerous shallow lakes, ponds, bogs, and streams.
Permafrost is the primary reason why trees cannot grow in the tundra. Their roots are unable to penetrate the frozen ground to secure anchorage or access deeper nutrients. This limitation shapes the entire vegetation structure, favoring low-growing plants that can survive with shallow root systems. The constant freezing and thawing of the active layer also churns the soil in a process called cryoturbation, further disrupting root systems and creating unique surface patterns like hummocks and polygons.
Tundra Flora and Fauna
Tundra vegetation is adapted to survive high winds, low temperatures, and the shallow, nutrient-poor soil of the active layer. Plants are low-growing and often form mats or cushions to protect themselves from the cold and wind. Common flora includes dwarf shrubs like the arctic willow, sedges, grasses, mosses, and a wide variety of lichens, such as reindeer moss, which is a food source for caribou. These plants have developed adaptations like growing in clumps for warmth and having hairy stems to trap heat.
Animal life in the tundra has evolved strategies to cope with the extreme environment. Some animals are year-round residents, while others migrate to warmer climates during the winter. Herbivores include lemmings, voles, arctic hares, caribou (known as reindeer in Eurasia), and musk oxen. Predators such as arctic foxes, wolves, polar bears, and snowy owls prey on these animals.
The arctic fox and ptarmigan change their coat colors from brown in summer to white in winter to camouflage themselves from predators or prey. Many animals, like the musk ox, have thick, insulating coats of fur, while smaller mammals like lemmings burrow under the snow to escape the cold and find food. Caribou undertake long-distance migrations, moving south to the boreal forest for the winter to find food and returning to the tundra in the summer to calve.
Human Activity and Environmental Changes
The arctic tundra is experiencing rapid changes due to human activities, primarily global warming. Rising global temperatures are causing the permafrost to thaw at an accelerated rate. This thawing has profound consequences, as it releases vast stores of carbon dioxide and methane, potent greenhouse gases that have been locked in the frozen ground for millennia. The release of these gases contributes to a feedback loop that further accelerates warming.
Thawing permafrost also destabilizes the landscape, creating uneven ground known as thermokarst and causing damage to infrastructure like buildings, roads, and pipelines built upon it. The tundra is also affected by oil and gas exploration and extraction. These industrial activities can lead to habitat fragmentation, disrupting the migration patterns of animals like caribou. Spills and pollution from these operations also threaten the fragile ecosystem.