Tundra Biome
The tundra is Earth's exposed edge — the treeless, wind-scoured plain that stretches between the last trees and the permanent ice. It is a biome of extremes and contradictions: one of the driest regions on Earth yet often waterlogged, almost devoid of trees yet home to hundreds of plant species, brutally cold for most of the year yet bursting with life in a brief, intense summer. The word tundra comes from the Finnish tuntura — an open, treeless plain — and it describes both the vast Arctic lowlands that encircle the North Pole and the high alpine zones found above the treeline on mountains worldwide.
- Area Coveredapprox. 20% of landArctic and alpine tundra combined
- LocationArctic + mountainsNorthern North America, Greenland, Russia; mountain tops globally
- Annual Rainfall200–600 mmLow — but permafrost traps meltwater at the surface
- Temperature−70°C to +12°CAverage annual temperature below 0°C in most areas
- Plant HeightCentimetresAll plants grow low to avoid the wind and cold
- TypesArctic + AlpineTwo distinct tundra types with shared characteristics
Where does tundra sit in the global rainfall spectrum?
Tundra is almost as dry as desert — yet it stays wet because of permafrost and frozen temperatures.
The tundra receives less precipitation than most people expect — comparable to many deserts. The crucial difference is temperature: cold conditions mean almost no water evaporates, and permafrost prevents drainage, so the landscape stays waterlogged despite minimal rain. In summer, the surface thaw creates thousands of lakes and boggy areas.
What is the Tundra Biome?
The tundra biome encompasses two distinct but ecologically similar environments: the Arctic Tundra and the Alpine Tundra. Arctic Tundra forms a vast circumpolar belt between the permanent polar ice cap and the boreal forest of the taiga, covering roughly 8 million square kilometres across northern Canada, Alaska, Greenland, Scandinavia and Siberia. Alpine Tundra forms above the treeline on mountains at all latitudes — from the Himalayas and the Alps to the Andes, the Rockies, Mount Kilimanjaro in Africa and even tropical mountain peaks close to the equator. Despite being geographically separated, the two types share the same defining characteristics: low temperatures, short growing seasons, strong winds, low plant diversity and the absence of trees.
The tundra is defined ecologically rather than climatically. A tundra is not simply cold or dry — it is a biome where conditions prevent trees from establishing. The critical factor in the Arctic is permafrost: permanently frozen subsoil that prevents tree roots from anchoring deeply and prevents water draining away. In alpine tundra, it is a combination of cold temperatures, thin soils, intense UV radiation and short growing seasons. Where trees cannot grow, the tundra community of grasses, sedges, mosses, lichens and dwarf shrubs takes over.
Arctic Tundra: location and landscape
The Arctic Tundra forms a nearly continuous ring around the North Pole, immediately south of the permanent sea ice and north of the taiga forest. Major Arctic Tundra regions include the North Slope of Alaska (home of the Arctic National Wildlife Refuge), the Canadian Arctic Archipelago and Hudson Bay lowlands, most of Greenland outside the central ice sheet, Svalbard (Norway), northern Scandinavia (the Scandinavian fell), and vast stretches of Siberia in Russia — the largest single tundra landmass on Earth. The Yamal and Gydan peninsulas of western Siberia, where permafrost is melting rapidly, have made international news as enormous craters — up to 30 metres across — have appeared suddenly where methane gas pressure built up beneath the thawing ground.
Alpine Tundra: mountains above the treeline
Alpine Tundra is found above the treeline on mountains worldwide, regardless of latitude. In the European Alps, the treeline sits at around 2,000–2,200 metres; above it lies alpine meadow and then bare rock and ice. In the Himalayas, the treeline reaches 3,500–4,000 metres; in the tropical Andes, it can be as high as 4,500 metres. Alpine Tundra supports its own distinctive communities: Himalayan blue poppies, Andean puna grasslands with vicuñas and Andean condors, Rocky Mountain fell-fields with pikas and marmots, and the snow leopard's domain in Central Asian ranges. Alpine ecosystems are equally threatened by climate change — the treeline is advancing upwards, squeezing alpine species into smaller and smaller zones of suitable habitat at the top of mountains from which there is literally nowhere higher to go.
Climate and the permafrost cycle
The Arctic Tundra climate is defined by the permafrost beneath it. Permafrost — ground that stays frozen year-round — extends to depths of up to 450 metres in parts of Siberia and is continuous beneath all of the Arctic Tundra. In summer, only the top 30–100 cm — the "active layer" — thaws. This thin layer is where all tundra life happens: where roots grow, where insects hatch, where birds nest, where meltwater pools. The freeze-thaw cycle of the active layer creates remarkable landscape features — frost polygons (geometric networks of ice-wedge ridges visible from above), pingos (ice-cored hills), thermokarst lakes (formed when ice melts below ground) and solifluction terraces (where waterlogged soil slowly flows downhill over the frozen layer below).
Winters last eight to nine months, temperatures plunge to −40°C to −70°C, and the sun does not rise at all for weeks around the winter solstice. Summer arrives abruptly, bringing almost continuous daylight for weeks around the summer solstice — the "midnight sun" — and temperatures briefly reaching 3–12°C. This intensity of summer light drives a burst of plant growth, insect activity and animal behaviour compressed into just 8–10 weeks.
Plants and animals of the Tundra
About 1,700 plant species survive on the Arctic Tundra, all adapted to grow low, fast and efficiently. Arctic mosses and lichens are the foundation, covering vast areas and providing the main food source for caribou. Sedges and cotton grasses grow in the wettest areas. Dwarf willows and dwarf birches creep along the ground — ancient trees in miniature, sometimes growing just 2–3 cm per year. In summer, the tundra bursts into colour with hundreds of flowering plants — saxifrages, Arctic poppies, mountain avens and purple saxifrage — that must complete their entire life cycle in weeks.
Tundra animals include some of the most specialised cold-adapted species on Earth: the polar bear with its hollow insulating fur and thick blubber; the Arctic fox that can survive −70°C with the world's most insulating coat; the musk ox, unchanged from the Ice Age, with underwool (qiviut) eight times warmer than sheep's wool; and the caribou, which migrates hundreds of kilometres following snowmelt and grazing. Lemmings drive population cycles that cascade through snowy owls, Arctic foxes and long-tailed skuas. Millions of migratory birds — geese, ducks, waders and terns — fly from every part of the world to breed on the tundra each summer.
Tundra food web
The tundra food web is one of the most studied in ecology because its relative simplicity makes the connections between species unusually clear. Producers — mosses, lichens, sedges, grasses and dwarf shrubs — form the base, converting the brief summer sunshine into plant material. Caribou are the dominant large herbivores of the Arctic Tundra, consuming lichens and grasses; a single herd may number in the hundreds of thousands and migrate over 1,000 km. Musk oxen graze year-round, digging through snow to reach buried vegetation. Lemmings and voles are the most important small herbivores, feeding on grasses and sedges under the snow in winter. These small rodents are the keystone of the tundra food web: when their populations peak (every 3–4 years), snowy owls raise broods of up to 11 chicks (instead of the usual 3–5), Arctic foxes have large litters, and rough-legged hawks breed successfully. When lemming populations crash, all these predators suffer. Snowy owls may erupt southward into Europe or North America in "irruption years" when northern prey fails. Wolves hunt caribou. Polar bears sit atop the marine-tundra food chain, hunting ringed and bearded seals on the sea ice; seals prey on Arctic cod and other fish, which in turn feed on copepods and krill, which feed on ice algae. Arctic terns and other seabirds feed on fish and invertebrates in the ocean and transport marine nutrients onto land as guano.
How animals adapt to the Tundra
Tundra animals have evolved some of the most extreme cold-weather adaptations of any creatures on Earth. The polar bear's fur is not actually white — it is translucent, appearing white by scattering light. Its skin beneath is black, absorbing solar radiation. Each hollow hair shaft traps warm air close to the body. A 10 cm layer of blubber provides further insulation and an energy reserve when food is scarce. Polar bear paws are covered in small bumps (papillae) that grip ice, and partially webbed for efficient swimming — they have been tracked swimming 100 km or more across open water. The musk ox grows qiviut — a downy underfur shed each spring — that is among the finest natural insulating fibres known, eight times warmer than sheep's wool by weight. During blizzards, musk oxen huddle facing outward in a circle, calves in the centre, presenting a wall of horns to any attacking wolf pack. Ptarmigan (tundra grouse) change plumage three times a year — brown in summer, white in winter, mottled in spring and autumn — and grow feathers on their feet in winter that act as snowshoes and add insulation. The Arctic ground squirrel achieves the deepest hibernation of any warm-blooded animal: its body temperature drops below 0°C (to around −2.9°C) for weeks at a time without ice crystals forming in its tissues, a feat made possible by a supercooling mechanism that prevents ice nucleation. Lemmings excavate elaborate tunnel systems beneath the snow where they breed throughout the winter in relative warmth.
Threats and conservation
The tundra is warming faster than almost any other biome — the Arctic is heating at nearly four times the global average rate. Permafrost thaw is destabilising coastlines, infrastructure and ecosystems; the release of stored carbon is amplifying warming in a runaway feedback. Polar bears face starvation as sea ice disappears. Caribou herds are declining as changing snowfall patterns make forage harder to reach in winter. Oil and gas development in Arctic regions — particularly in Alaska's North Slope and Russia's Yamal Peninsula — has created infrastructure that fragments habitat and poses pollution risks. Plastic pollution from distant human sources accumulates in Arctic food webs, concentrating in seabirds, seals and polar bears. Alpine tundra is being squeezed from below as the treeline rises with warming temperatures, reducing habitat for high-altitude specialists.
Deeper dive: permafrost feedback and the carbon time bomb
Permafrost is one of the most important — and most concerning — features of the tundra. It forms where the average annual temperature is below 0°C and has been accumulating for thousands to tens of thousands of years. The permafrost is not just frozen soil: it is a vast repository of partly decomposed plant and animal material preserved by freezing. In some areas of Siberia, woolly mammoths that died 40,000 years ago emerge perfectly preserved from eroding riverbanks.
As the Arctic warms, the active layer deepens each year, thawing more permafrost. The microbes that were frozen in the permafrost awaken and begin decomposing the ancient organic material. This releases carbon dioxide and — particularly in waterlogged, oxygen-poor conditions — methane. Methane is 80 times more potent than CO₂ as a greenhouse gas over a 20-year period. Scientists estimate the permafrost contains approx. 1.7 trillion tonnes of carbon. Climate models suggest that even under moderate warming scenarios, permafrost thaw could release the equivalent of 1.5 to 2.1 times the total carbon already emitted by all human activity in history by 2100. This "permafrost carbon feedback" is one of the most alarming potential tipping points in the Earth's climate system, and monitoring it is now a major priority of Arctic science.
The tundra is the most fragile of all biomes in the face of climate change — and possibly the one whose transformation will have the greatest consequences for the rest of the planet. The biome immediately south of it — the great coniferous forests of the Taiga Biome — faces similar threats but on a vaster scale.