Peatlands exist in the mountains, in lowlands, along rivers and at the coast. Their vegetation and condition vary from one climate zone to another, but all types of peatland have one thing in common: their continued existence is in danger.
Ever since the 17th century, peatlands have been systematically drained – for peat extraction, settlement, forestry and farming. Beginning in the second half of the 20th century, the industrialization of agriculture accelerated large-scale drainage, especially in temperate zone of the northern hemisphere. As a result, some industrialized countries now have little of their natural peatlands left. Worldwide, over 50 million hectares are currently covered by drained peatlands, and the trend is rising.
In many countries and especially in the Global South there is little data on peatlands. Only enhanced mapping will reveal the true extent of peatland drainage and its consequences for climate crisis. What is certain: worldwide, peatlands are often found in climate zones that mostly have either very high rainfall or very cold temperatures – or both. These are mainly in the tropics at a band around the Equator and in the sub-arctic, boreal and temperate oceanic zones of both the northern and southern hemispheres. The climatic conditions in these regions cause biomass to be broken down only very slowly, favouring the formation of peat.
Peatlands are relatively less widespread in subtropical regions because moisture is scarcer in these areas. But even here, peat formation is possible under certain circumstances. Some areas receive enough water from large rivers from regions with higher precipitation, such as mountain ranges. As a result peatlands can develop in lowlands and in the deltas of large rivers such as the Brahmaputra in Bangladesh, the Rio Paraná in Argentina, and the Zambezi in Zambia. The total area of peatlands around the globe is estimated at 500 million hectares. But this figure is just an approximation: many large areas are imprecisely mapped, and innumerable smaller peatlands remain undiscovered.
Peatlands occur along coasts worldwide, in saltmarshes and saline reedbeds, and in the tropics often in mangroves – coastal woodlands in areas where seawater and freshwater mix. Peat formation is favoured by marine currents and the humid air masses that are associated with them, such as along Europe’s western sea coast and in the Caribbean. On land, flat terrain slows down the natural flow of water on the land surface, resulting in the creation of the huge peatlands in western Siberia, Southeast Asia, the Congo Basin and the western Amazon. Finally, peat can occur anywhere where the local climate and terrain permit permanently high and stable water levels in the soil.
These differences in climate, water source, water quality and the resulting vegetation produce diverse types of peatland. Essentially they all have one feature in common: the presence of a layer of peat in the soil.
In cold subarctic and boreal cool humid oceanic regions, the peat forms mainly from the remains of mosses. Especially in Siberia and over vast areas of Canada and Alaska, fairly treeless peat landscapes are found: seemingly endless expanses dominated by mosses. In the temperate continental and subtropical parts of the world, grass-like plants such as reeds, sedges and rushes take over the role of peat producers and dominate the peatland vegetation. Here, the peat accumulates in the first few feet under the surface, as the underground shoots and roots of these plants grow into the older peat material where they die off. These peatlands reside as grasslands with reed beds of various sizes along rivers, in silted-up lakes and in depressions of different sizes. In tropical lowlands, the peat is often formed by the deep roots of tall trees. Huge, forested peat landscapes cover these tropical peatlands for example in the Congo Basin, Indonesia and Peru.
For the last 20 years these peat swamp forests of the tropics have been increasingly deforested, drained and used for timber production and intensive agricultural production. For many years the hotspot of this trend was in Southeast Asia, especially Indonesia. Infrastructure development and clearing are now increasingly taking place in the extensive peatlands of the Congo and Amazon basins. A further threat to peatlands not only in the subtropics of Africa and South America: the climate crisis.