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In physical geography, a wetland is an environment "at the interface between truly terrestrial ecosystems...and truly aquatic systems...making them different from each yet highly dependent on both" (Mitsch & Gosselink, 1986). In essence, wetlands are ecotones. Wetlands are found under a wide range of hydrological conditions, but at least some of the time water saturates the soil. The result is a hydric soil , one characterized by an absence of free oxygen some or all of the time, and therefore called a " reducing environment." Plants (called hydrophytes or just wetland plants) specifically adapted to the reducing conditions presented by such soils can survive in wetlands, whereas species (called "upland" plants) intolerant of the absence of soil oxygen can not survive. Adaptations to low soil oxygen characterize many wetland species.

1 Wetland types

• bog or moor or muskeg (peatlands)
• marsh or fen
• swampA swamp is a wetland that features permanent inundation of large areas of land by shallow bodies of water, generally with a substantial number of hummocks, or dry-land protrusions. Swamps usually are regarded as including a large amount of woody vegetatio
• bayouA bayou (pronounced "by-you" or "by-yoe") is a body of water tributary to a lake or a river. Bayous are usually located in low-lying areas, especially in the Mississippi River delta region of the southern United States. Crawfish, certain species of shrimp or sloughThe term slough (In the UK, pronounced to rhyme with bough; In the US, pronounced "slew") has several meanings related to wetland or aquatic features that seem to derive from local experience. For example: In the UK, a slough is a muddy or marshy area (fo
• constructed wetlandA constructed wetland is an artificial marsh or swamp, created for human use, such as wastewater or sewage treatment, as habitat to attract wildlife, or for land reclamation after mining or other disturbance. Natural wetlands act as biofilters, removing s

2 Wetland functions

By absorbing the force of strong windFor the 1928 film, see The Wind. Wind in the most general sense, is the movement of air. It occurs at all scales, from local breezes generated by heating of land surfaces and lasting tens of minutes to global winds resulting from solar heating of the plans and tideThe tide is the regular rising and falling of the ocean's surface caused by changes in gravitational forces external to the Earth. The primary changing gravitational field is due to the Moon while the secondary field is caused by the Sun. Types of tides Ts, wetlands protect terrestrial areas adjoining them from stormEnschede, The Netherlands. A storm is a kind of severe weather marked by hard wind (a wind storm), thunder and lightning (a thunderstorm), heavy precipitation such as ice ( ice storm), or wind transporting some substance through the atmosphere (as in a dus, floods, and tidalThe tide is the regular rising and falling of the ocean's surface caused by changes in gravitational forces external to the Earth. The primary changing gravitational field is due to the Moon while the secondary field is caused by the Sun. Types of tides T damage. Fresh water marshes are often on river floodplains.

A temperate wetland in Britain, with shallow open water and reedbeds.

Wetlands are often filled in to be used for everything from agriculture to parking lots, in part because the economic value of wetlands has only been recognised recently: the shrimp and fish that breed in salt water marshes are generally harvested in deeper water, for example. Wetlands support a wide variety of wildlife (bird, plants, fish, mammals etc) and therefore the conservation of wetlands is of prime importance for the preservation of many species of wildlife. In 1962, the idea of wetlands conservation was born with a "List of Wetlands of International Importance". This was followed up in 1971 by the Ramsar Convention when conservationists from 23 countries met in the city of Ramsar, Iran on the shores of the Caspian Sea. There are now over 1,200 wetlands on the Ramsar List.