A wetland is an area of land whose soil is saturated with moisture either permanently or seasonally. Such areas may also be covered partially or completely by shallow pools of water. Wetlands include swamps, marshes, and bogs, among others. The water found in wetlands can be saltwater, freshwater, or brackish. The world's largest wetland is the Pantanal which straddles Brazil, Bolivia and Paraguay in South America.

Wetlands are considered the most biologically diverse of all ecosystems. Plant life found in wetlands includes mangrove, water lilies, cattails, sedges, tamarack, black spruce, cypress, gum, and many others. Animal life includes many different amphibians, reptiles, birds, insects, and mammals.

In many locations, such as the United Kingdom, Iraq, South Africa and the United States, wetlands are the subject of conservation efforts and Biodiversity Action Plans.

Wetlands also serve as natural wastewater purification systems—e.g., in Calcutta and Arcata.

The study of wetlands has recently been termed paludology in some publications.

Technical definitions

Wetlands have been categorized both as biomes and ecosystems. A patch of land that develops pools of water after a rain storm would not be considered a "wetland" though the land is wet. Wetlands have unique characteristics: they are generally distinguished from other water bodies or landforms based on their water level and on the types of plants that thrive within them. Specifically, wetlands are characterized as having a water table that stands at or near the land surface for a long enough season each year to support aquatic plants. Put simply, wetlands are lands made up of hydric soil.

Wetlands have also been described as ecotones, providing a transition between dry land and water bodies. Mitsch and Gosselink write that wetlands exist "...at the interface between truly terrestrial ecosystems and aquatic systems, making them inherently different from each other, yet highly dependent on both."

Ramsar Convention definition

Under the Ramsar international wetland conservation treaty, wetlands are defined as follows:

Article 1.1: "...wetlands are areas of marsh, fen, peatland or water, whether natural or artificial, permanent or temporary, with water that is static or flowing, fresh, brackish or salt, including areas of marine water the depth of which at low tide does not exceed six metres."

Article 2.1: "[Wetlands] may incorporate riparian and coastal zones adjacent to the wetlands, and islands or bodies of marine water deeper than six metres at low tide lying within the wetlands".

Regional definitions

In the United States, wetlands are defined as "those areas that are inundated or saturated by surface or groundwater at a frequency and duration sufficient to support, and that under normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated soil conditions. Wetlands generally include swamps, marshes, bogs and similar areas". Some US states, such as Massachusetts and New York, have separate definitions that may differ from the federal government.

Wetlands and climate change

Wetlands perform two important functions in relation to climate change. They have mitigation effects through their ability to sink carbon, and adaptation effects through their ability to store and regulate water.

Mitigation

Peatswamp forests and soils are being drained, burnt, mined, and overgrazed contributing severely to climate change. As peatlands form only 3% of all the world’s land area, their degradation equal 7% of all fossil fuel carbon dioxide (CO₂) emissions. As a result of peat drainage, the organic carbon that was built up over thousands of years and is normally under water, is suddenly exposed to the air. It decomposes and turns into carbon dioxide (CO₂), which is released into the atmosphere. Peat fires cause the same process and in addition create enormous clouds of smoke that cross international borders, such as happen every year in Southeast Asia.

Through the building of dams, Wetlands International is halting the drainage of peatlands in Southeast Asia, thereby avoiding enormous CO₂ emissions. Reforestation with native tree species as well as setting up community fire brigades are also part of an integral, very cost effective approach shown in Central Kalimantan and Sumatra, Indonesia. (from: www.wetlands.org)

Adaptation

Mangroves, floodplains, highland and other wetlands can reduce the impacts of increased precipitation, storms, glacier melting and even sealevel rise. The water regulating and storage functions of these wetlands are crucial in adapting to a changing climate. Therefore, in order to protect people living close or even far downstream from wetlands and their source of livelihoods, we must conserve and restore wetlands. In this way, they can continue to play their critical role. (from www.wetlands.org)

Conservation

Wetlands have historically been the victim of large-scale draining efforts for real estate development, or flooding for use as recreational lakes. By 1993 half the world's wetlands had been drained. Since the 1970s, more focus has been put on preserving wetlands for their natural function — sometimes also at great expense. Wetlands provide a valuable flood control function. Wetlands are very effective at filtering and cleaning water pollution, (often from agricultural runoff from the farms that replaced the wetlands in the first place). To replace these wetland ecosystem services enormous amounts of money have been spent on water purification plants and remediation measures, constructing dams, levees and other artificial flood controls.

Balancing wetland conservation with the needs of people

Wetlands are vital ecosystems that provide livelihoods for the millions of people who live in and around them. The Millennium Development Goals (MDGs) called for different sectors to join forces to secure wetland environments in the context of sustainable development and improving human wellbeing. A three-year project carried out by Wetlands International in partnership with the International Water Management Institute found that it is possible to conserve wetlands while improving the livelihoods of people living among them. Case studies conducted in Malawi and Zambia looked at how dambos – wet, grassy valleys or depressions where water seeps to the surface – can be farmed sustainably to improve livelihoods. When mismanaged or overused dambos often become degraded, and this was starting to happen at the study sites. Project staff learned from local farmers how specific dambos functioned, and then trained them in relevant soil and water management practices, emphasising that dambos need to be managed with regard for the wider environment. Before the project, there were cases where people had died from starvation due to food shortages. By the end of it, many more people had access to enough water to grow vegetables. A key achievement was that villagers had secure food supplies during long, dry months. They also benefited in other ways: for example, they improved their nutrition by growing a wider range of crops, and could also invest in health and education by selling produce and saving money.

Ramsar Convention

''The Convention on Wetlands of International Importance, especially as Waterfowl Habitat'', or Ramsar Convention, is an international treaty designed to address global concerns regarding wetland loss and degradation. The primary purposes of the treaty are to list wetlands of international importance and to promote their wise use, with the ultimate goal of preserving the world's wetlands. Methods include restricting access to the majority portion of wetland areas, as well as educating the public to combat the misconception that wetlands are wastelands. The Convention works closely with five International Organisation Partners. These are: Birdlife International, IUCN, International Water Management Institute, Wetlands International and WWF. The partners provide technical expertise, help conduct or facilitate field studies and provide financial support. The IOPs also participate regularly as observers in all meetings of the Conference of the Parties and the Standing Committee and as full members of the Scientific and Technical Review Panel.

Conservation by country

New Zealand

Over 90% of the wetlands in New Zealand have been drained since European settlement, predominantly to create farmland. Wetlands now have a degree of protection under the Resource Management Act.

South Africa

The South African Department of Environmental Affairs and Tourism in conjunction with the departments of Water Affairs and Forestry, and of Agriculture, supports the conservation and rehabilitation of wetlands through the Working for Wetlands program. The aim of this program is to encourage the protection, rehabilitation and sustainable use of South African wetlands through co-operative governance and partnerships. The program is also a poverty relief effort, providing employment in wetland maintenance.

Sweden

The Swedish national wetland inventory (VMI) is one of the world's most extensive systematic inventories of nature types that has ever been done. VMI has surveyed the wetlands of Sweden below the alpine region during a 25-year period. In total 35 000 objects (sites) are included in VMI, corresponding to an area of 4.3 million hectares, or 10% of the land area of Sweden. The aim of the survey has been to increase the general knowledge of wetlands in Sweden, as a basis for environmental monitoring and natural resources planning. By investigating the impact of human activities on wetlands and identifying the most valuable wetlands, their values can be preserved for future generations. The results from the inventory were also meant to function as background data for the authorities' decisions concerning e.g. drainage permits.

United States

The USA came to understand how biologically productive wetlands are, so the USA passed laws limiting wetlands destruction, and created requirements that if a wetland had to be drained, developers at least had to offset the loss by creating artificial wetlands. One example is the project by the U.S. Army Corps of Engineers to control flooding and enhance development by taming the Everglades, a project which has now been reversed to restore much of the wetlands as a natural habitat for plant and animal life, as well as a method of flood control. Another project in the works to restore the Everglades is the U.S Sugar Corp Land Transaction. The project entails the acquisition of U.S. Sugar Corp. land, which would allow for water delivery, water treatment and water storage of sufficient quantity and quality to mimic the Everglades' natural system. The Everglades Foundation, a foundation whose mission is to protect and restore one of the world’s unique natural ecosystems, and other environment-based organizations support the state of Florida acting to secure U.S. Sugar Corp. land.

Republic of Macedonia

The fragments of wetland habitats that are still in existence in the Republic of Macedonia are present as marsh or swamp communities. These patches are present as Studenchishte (small fragment near Ohrid Lake), Pelagonia (village Chepigovo), Negortsi Spa, Bansko, Belchishte wetland and Monospitovo marsh. The large areas of swamps that use to be present in most of the valleys in contemporary Republic of Macedonia have undergone a great transformation over the last 50-60 years. The main cause for their reduction was land reclamation, drainage, and conversion into arable land for agricultural needs which lead to their fragmentation in general (Smith and Smith, 2003). As most threatened wetland ecosystems nowadays are considered the fragmented parts of relict communities that developed on organic soils and appear as most suitable for early vegetables after draining such as the Bansko swamp. Some of the remaining wetlands (Negortsi Spa, Bansko) are of great importance for understanding the genesis of marsh vegetation in the Republic of Macedonia. In addition, mountainous marshes and peat bogs also suffered anthropogenic transformation due to the capturing of water from mountain springs and streams for the purposes of generating drinking water (Smith, 2003). Accordingly, the fragmentation and transformation of previous swamps had a major impact on faunal distribution and abundance. Most affected are the amphibians and species of other invertebrate and vertebrate groups. One of the related threatened species is the European Otter (Lutra Lutra L.). It is listed as Nearly Threatened according to the red list and is still present in some of the swamps, especially in Belchishte wetland where the population of the Otter is still large (Smith 2003; Smith and Smith, 2003).Also some of the wetlands lie within the network of some of the bigger rivers in Macedonia. The Vardar River that drains into the Aegean Sea in Greece has the biggest catchment, 80% of Macedonian territory. The river catchment of Crni Drim is the second largest river in Macedonia, draining into the Adiratic Sea with 13%, followed by the river Strumica with 7% of the total catchment area in Macedonia (Poledník et al., 2008). The Otter has importance for the wetland communities not just in Macedonia but also in other European countries, such as The Netherlands and Germany (Reuther, 1995; Reuther et al., 2001).

Mapping

There are many remote sensing methods that can be used to map wetlands. Remote-sensing technology permits the acquisition of timely digital data on a repetitive basis. This repeat coverage allows wetlands, as well as the adjacent land-cover and land-use types, to be monitored seasonally and/or annually. Using digital data provides a standardized data-collection procedure and an opportunity for data integration within a geographic information system. Traditionally, Landsat 5 Thematic Mapper (TM), Landsat 7 Enhanced Thematic Mapper Plus (ETM + ), and the SPOT 4 and 5 satellite systems have been used for this purpose. More recently, however, multispectral IKONOS and QuickBird data, with spatial resolutions of 4m by 4m and 2.44m by 2.44 m, respectively, have been shown to be excellent sources of data when mapping and monitoring smaller wetland habitats and vegetation communities.

A wide range of remote sensing studies has been undertaken in a variety of wetland environments. Remote sensing technology has permitted the acquisition of timely digital data on a repetitive basis. For example, the wetlands and vegetation within Detroit Lakes Wetland management District has been assessed using remote sensing. In mapping and monitoring large geographic areas, analysis of satellite images is less costly and time-consuming compared to visual interpretation of aerial photographs. Aerial photographs also require experienced interpreters to extract information based on structure and texture while remote sensing only requires the analysis of the spectral characteristics of data.

However, there are a number of limitations associated with image acquisition. Analysis of wetlands has proved difficult because to obtain the data, it has to be linked with practical purposes such as the analysis of land cover or land use. Wetlands, in particular are difficult to monitor, are often difficult to access, especially their inner reaches, and are sometimes home to dangerous wildlife and endemic diseases. Developing a global inventory of wetlands has proven to be a large and difficult undertaking. Current efforts are based on available data, but both classification and spatial resolution may be inadequate for regional or site-specific management decision-making. It is difficult to identify small, long, and narrow wetlands within the landscape. Current efforts using today’s remote sensing satellites may not have sufficient spatial and spectral resolution to monitor wetland conditions, although multispectral IKONOS and QuickBird data may offer improved spatial resolutions of 4m or higher. Majority of the pixels are just mixtures of several plant species or vegetation types and are difficult to isolate. Improved remote sensing information, coupled with good knowledge domain on wetlands will facilitate expanded efforts in wetland monitoring and mapping. This will also be extremely important because we expect to see major shifts in species composition due to both anthropogenic (land use) and natural changes in the environment caused by climate change. Methods to focus the classification on specific classes of interest so that identification can be done with very high accuracies should be looked into. The issue of the cost and expertise involved in remote sensing technology is still a factor hindering further advancements in image acquisition and data processing. Future improvements in wetland vegetation mapping could include the use of more recent and better geospatial data.

Climates

Temperature

Temperatures vary greatly depending on the location of the wetland. Many of the world's wetlands are in temperate zones (midway between the North or South Pole and the equator). In these zones, summers are warm and winters are cold, but temperatures are not extreme. However, wetlands found in the tropic zone, around the equator, are warm year round. Wetlands on the Arabian Peninsula, for example, can reach 50 °C (122 °F) and would therefore be subject to rapid evaporation. In northeastern Siberia, which has a polar climate, wetland temperatures can be as low as −50 °C (−58 °F). And in a moderate zone, such as the Gulf of Mexico, a typical temperature might be 11 °C (51 °F).

Rainfall

The amount of rainfall a wetland receives varies widely according to its location. Wetlands in Wales, Scotland, and Western Ireland typically receive about 1500 mm (or 60 in) per year. In some places in Southeast Asia, where heavy rains occur, they can receive up to 10,000 mm (about 200 in). In the northern areas of North America, wetlands exist where as little as 180 mm (7 inches) of rain fall each year.

List of wetland types

Swamp

*Freshwater swamp forest

*Coniferous swamp

Marsh

*Salt marsh

Bog

*Peat swamp forest

Slough

Flooded grasslands and savannas

Constructed wetland

Riparian zone

Fen

Vernal Pool

See also

Converted wetland

Saline marshlands

Wetland conservation

References

Wetlands International Wetlands International Africa Wetlands International Latin America & the Caribbean Wetlands International Indonesia Wetlands International Japan Ramsar Convention on Wetlands

Further reading

Mitsch, W.J., J.G. Gosselink, C.J. Anderson, and L. Zhang. (2009) "Wetland Ecosystems". John Wiley & Sons, Inc., New York, 295 pp.

Ghabo, A. A. (2007) Wetlands Characterization; Use by Local Communities and Role in Supporting Biodiversity in the Semiarid Ijara District, Kenya. Terra Nuova East Africa. Wetlands in drylands.

1987 U.S. Army Corps of Engineers Wetland delineation manual

Dugan, Patrick (editor) (1993) ''Wetlands in Danger'', World Conservation Atlas Series

Brinson, M. (1993) A Hydrogeomorphic Classification of Wetlands

Fredrikson, Leigh H. (1983) "Wetlands: A Vanishing Resource" Yearbook of Agriculture

W.H. MacKenzie and J.R. Moran (2004) "Wetlands of British Columbia: A Guide to Identification. Ministry of Forests, Land Management Handbook 52.

External links

Wetlands International - A non-profit global organisation to sustain and restore wetlands, their resources and biodiversity for future generations

WetlandInfo: Queensland Department Environment and Natural Resource

US Fish & Wildlife Service: National Wetlands Inventory

Wetlands: The Ecological Effect of Loss (Research article)

Pôle-relais zones humides littorales de la façade atlantique, Manche et Mer du Nord

Marshlands of Iberá (in English and Spanish)

Wetlands Water Quality Information Center, U.S. Department of Agriculture

Centro Studi Naturalistici

Wetlands legal updates

Wetland of Hong Kong

Forum des Marais Atlantiques - Pôle-relais zones humides littorales de la façade atlantique, Manche et Mer du Nord

Category:Terrestrial biomes Category:Habitat (ecology) terminology Category:Environmental terminology Category:Aquatic ecology Category:Freshwater ecology

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