The Arctic tundra is a desert that turns into marshland every summer
Arctic tundra gets only 150 to 250 millimetres of precipitation a year, as little as many deserts. Yet in summer it is a maze of bogs, lakes and streams, because frozen ground a short way down stops meltwater from draining. That frozen soil also locks away vast amounts of carbon now beginning to escape.
Tundra is any biome where cold and short growing seasons keep trees out, and it comes in Arctic, alpine and Antarctic forms. The word reached English in 1824, spelled toundra, from Russian; the Russian term may come from a Sámi word for an elevated wasteland or marshy plain, and some trace it instead to Finnish tunturi, a treeless plain. Plant life means dwarf shrubs, sedges, grasses, mosses and lichens, with the boundary to forest known as the tree line.
North of the taiga, Arctic tundra stays frozen most of the year, with permanently frozen subsoil starting 25 to 90 centimetres down. Winter averages around minus 28 °C and can hit minus 50 °C, although the very lowest temperatures in Russia, Canada and Alaska were recorded south of the tree line. Summer days reach about 12 °C, winds often blow at 50 to 100 kilometres per hour, and only about 1,700 vascular plant species and 48 land mammals live there, from musk oxen and lemmings to Arctic foxes. Millions of migrating birds arrive for the marshes, while cold-blooded animals like frogs and lizards are largely absent. Nomadic reindeer herders such as the Nenets and Nganasan make it home.
The soil is a carbon store, holding decomposed plant matter as methane and carbon dioxide within the permafrost. Warming thaws it, releasing gases that cause further warming, a positive feedback. The IPCC's Sixth Assessment estimates releases equivalent to 14 to 175 billion tonnes of carbon dioxide per degree of warming, against human emissions of about 40 billion tonnes a year by 2019. Thaw also threatens roads and pipelines, and fires such as the 1,039 square kilometres that burned on Alaska's Brooks Range north slope in 2007 add to the problem. The Yamalo-Nenets region alone supplies 90 percent of Russia's natural gas.
Antarctic tundra is mostly lichens, mosses, liverworts and algae clinging to exposed coastal rock, plus just two flowering plants, Antarctic hair grass and Antarctic pearlwort, on the Antarctic Peninsula. Isolation means no large land mammals, only seals and penguins on the shore. Alpine tundra occurs on mountains worldwide, better drained than Arctic ground and edged by stunted Krummholz forest.
Source: Tundra
