Arctic tundra occurs in the far Northern Hemisphere, north of the taiga belt. The word "tundra" usually refers only to the areas where the subsoil is permafrost, which means permanently frozen soil. (It may also refer to the treeless plain in general, so that northern Lapland would be included.) Permafrost tundra includes vast areas of northern Russia and Canada •. The polar tundra is home to several peoples who are mostly nomadic reindeer herders, such as the Nganasan and Nenets in the permafrost area (and the Sami in Lapland).

The arctic tundra is a vast area of stark landscape, which is frozen for much of the year. The soil there is frozen from 25-90 cm (9.8-35.4 inches) down, and it is impossible for trees to grow. Instead, bare and sometimes rocky land can only support low growing plants such as mosses, heaths and lichen. There are two main seasons – winter and summer in the polar Tundra areas. During the winter, it is very cold and dark, with the average temperature around -28 °C (-18.4°F), sometimes dipping as low as -70 °C (-94°F). In the summer, temperatures rise and the top layer of the permafrost melts, leaving the ground very soggy. The tundra is covered in marshes, lakes, bogs and streams. Generally temperatures during the summer rise to about 12 °C (53.6°F), but can often drop to 3° (37.4°F). Arctic tundras are sometimes the subject of habitat conservation programs. In Canada and Russia many of these areas are protected through a national Biodiversity Action Plan.

The tundra is a very windy area, with winds blowing upwards of 48–97 km/h (30-60 miles an hour). However in terms of precipitation, it is desert-like, with only about 150–250 mm (6–10 inches) falling a year (mostly of snow). During the summer, the permafrost thaws just enough to let plants grow and reproduce, but because the ground below this is frozen, the water cannot sink any lower, and so the water forms the lakes and marshes found during the summer months.

The biodiversity of the tundras is low: there are 1700 species of flora and only 48 land mammals that can be found, although thousands of insects and plants migrate there each year for the marshes. There are also a few fish species such as the flat fish. There are few species with large populations. Notable animals in the arctic tundra include caribou (reindeer), musk ox, arctic hare, arctic fox, snowy owl, lemmings, and polar bears (only the extreme north) •.

Due to the harsh climate of the arctic tundra, regions of this kind have seen little human activity, even though they are sometimes rich in natural resources such as oil and uranium. In recent times this has begun to change in Alaska, Russia, and some other parts of the world.

A severe threat to the tundras, specifically the permafrost, is global warming. Permafrost is essentially a frozen bog; in the summer, only its surface layer melts. The melting of the permafrost in a given area on human time scales (decades or centuries) could radically change which species can survive there•.

Another concern is that about one third of the world's soil-bound carbon is in taiga and tundra areas. When the permafrost melts, it releases carbon, in the form of carbon dioxide, a greenhouse gas. The effect has been observed in Alaska. In the 1970s, the tundra was a carbon sink, but today, it is a carbon source•.