Nature · Earth Science
Earth’s frozen frontiers, treeless and vast
The tundra is a cold, treeless biome where the ground stays frozen for most — or all — of the year. Spanning the northern edges of continents and the highest mountains, and merging into the true polar deserts of the Arctic and Antarctic, these are the coldest, harshest and most fragile landscapes on Earth.
Long, dark winters and brief, cool summers keep temperatures too low for trees to grow. Beneath a thin surface layer that thaws each summer lies permafrost — permanently frozen ground — which traps water at the surface, creating boggy pools, patterned ground and a delicate ecosystem adapted to extreme cold.
A thin summer "active layer" thaws above permanently frozen permafrost, shaping pools, patterned ground and hardy low plants.
The frozen rim of the north
Ringing the Arctic Ocean, this tundra bursts briefly into life each summer as the active layer thaws, drawing vast herds and millions of nesting birds before the long freeze returns.
Tundra above the treeline
On high mountains everywhere, even near the equator, cold and wind keep trees out. Alpine tundra plants hug the ground in cushions to survive fierce wind and nightly frost.
Where almost nothing grows
The interiors of Greenland and Antarctica are true cold deserts — bone-dry, buried under kilometres of ancient ice, and among the most lifeless places on the planet.
Ground sculpted by freeze and thaw
Repeated freezing and thawing sorts stones and cracks the surface into eerie geometric polygons and mounds. The frozen soil locks away vast carbon, making it a key player in the climate system.