Types of wetlands
All shapes and sizes
Wetlands are highly productive ecosystems that provide the world with nearly two-thirds of its fish harvest.
They take many forms, examples include: marshes, estuaries, mudflats, mires, ponds, fens, pocosins, swamps, deltas, coral reefs, billabongs, lagoons, shallow seas, bogs, lakes, and floodplains.
Almost every country in the world possesses a wetland of some description. Some are seasonally aquatic, some seasonally terrestrial. All play a vital role for humans and nature alike.
Mangrove swamps are forested ecosytems found at sheltered tropical coastal areas. The partly submerged roots of mangrove trees spread out beneath the water to trap sediment and prevent it being washed out to sea. Around 70% of tropical coastlines are mangrove-lined.
Some mangroves are strategically planted between land and sea to stabilise shores and to protect communities from violent storms and powerful waves. The result is an area of stillness and tranquillity where fish breed, wildlife takes refuge, and local people earn a living from occupations as diverse as charcoal burning and bee keeping.
Floodplains are areas of flat land seasonally flooded by rivers and lakes. Seasonal flooding is a natural phenomenon in most of the world’s rivers.
Inland floodplains and coastal deltas are the natural overflow areas that slow the velocity of the floodwaters, allowing nutrients and sediments to settle. These rich floodplains and deltas have sustained populations for thousands of years but continue to do so only in a limited number of cases.
Bogs
Bogs are waterlogged peatlands in old lake basins or depressions in the landscape. Almost all water in bogs comes from rainfall. Bogs have specialised and unique flora that have evolved in their nutrient-poor and acidic conditions, including for example the carnivorous pitcher plant. As bogs are unsuitable for agriculture, forestry or development they offer an undisturbed habitat for a wide range of species, including moose, black bear, lynx, snowshoe hare and mink.
In addition, bogs are used by many species of migratory birds, providing a safe habitat in which to breed, rest and feed.
Pocosins
Pocosins are evergreen shrub bogs found on the coastal plain of the southeastern United States. They are typically found on high areas of a flat water-logged landscape. The word is native American in origin, meaning ‘swamp on a hill’.
Fens
Like bogs, fens were formed when glaciers retreated. Unlike bogs, some of the water in fens comes from small streams and groundwater. This water movement means fens are less acidic so their soil and water are richer in nutrients.
Vernal pools
Vernal or spring pools are small, shallow, intermittently flooded depressions in grasslands or forests, and are usually only wet in winter and early spring.
Vernal pools are critical habitats for the lufe cycles of some animals, including a number of amphibians, which rely on them exclusively.
Marshes
Marshes are one of the broadest categories of wetlands and in general harbour the greatest biological diversity. Marshes form in depressions in the landscape, as fringes around lakes, and along slow-flowing streams and rivers. Marshes are dominated by floating-leafed plants like water lillies and duckweed. Marshes slow down the rate of rainfall drainage and control its flow into rivers, lakes, and streams.
These brief descriptions serve to illustrate the variety of wetlands. However, despite such diversity, all these different types of wetlands have one thing in common - they are all threatened.
