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A swamp is a wetland that is forested. Many swamps occur along large rivers where they are critically dependent upon natural water level fluctuations. Other swamps occur on the shores of large lakes. Some swamps have hammocks, or dry-land protrusions, covered by aquatic vegetation, or vegetation that tolerates periodic inundation. The two main types of swamp are "true" or swamp forests and "transitional" or shrub swamps. In the boreal regions of Canada, the word swamp is colloquially used for what is more correctly termed a bog or muskeg. The water of a swamp may be fresh water, brackish water or seawater. Some of the world's largest swamps are found along major rivers such as the Amazon, the Mississippi, and the Congo.
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Geomorphology and hydrology
Swamps are characterized by slow-moving to stagnant waters. They are usually associated with adjacent rivers or lakes. Swamps are features of areas with very low topographic relief. Swamps generate coal as rock.
Draining
Historically, humans have drained swamps to provide additional land for agriculture and to reduce the threat of diseases borne by swamp insects and similar animals. Many swamps have also undergone intensive logging, requiring the construction of drainage ditches and canals. These ditches and canals contributed to drainage and, along the coast, allowed salt water to intrude, converting swamps to marsh or even to open water. Large areas of swamp were therefore lost or degraded. Louisiana provides a classic example of wetland loss from these combined factors. Europe has probably lost nearly half its wetlands. New Zealand lost 90 percent of its wetlands over a period of 150 years. Ecologists recognise that swamps provide valuable ecological services including flood control, fish production, water purification, carbon storage, and wildlife habitat. In many parts of the world authorities protect swamps. In parts of Europe and North America, swamp restoration projects are becoming widespread. Often the simplest steps to restoring swamps involve plugging drainage ditches and removing levees.
Land value, productivity and conservation
Swamps and other wetlands have traditionally held a very low property value compared to fields, prairies, or woodlands. They have a reputation for being unproductive land that cannot easily be utilized for human activities, other than perhaps hunting and trapping. Farmers, for example, typically drained swamps next to their fields so as to gain more land usable for planting crops.
Many societies now realize that swamps are critically important to providing fresh water and oxygen to all life, and that they are often breeding grounds for a wide variety of life. Indeed, floodplain swamps are extremely important in fish production. Government environmental agencies (such as the United States Environmental Protection Agency) are taking steps to protect and preserve swamps and other wetlands. In Europe, major effort is being invested in the restoration of swamp forests along rivers. Conservationists work to preserve swamps such as those in northwest Indiana in the United States Midwest that were preserved as part of the Indiana Dunes.
Notable examples
Swamps can be found on all continents except Antarctica.
The largest swamp in the world is the Amazon River floodplain, which is particularly significant for its large number of fish and tree species.
Africa
The Sudd and the Okavango Delta are Africa's best known marshland areas.
Asia
The Tigris-Euphrates river system is a large swamp and river system in southern Iraq, traditionally inhabited in part by the Marsh Arabs.
In Asia, tropical peat swamps are located in mainland East Asia and Southeast Asia. In Southeast Asia, peatlands are mainly found in low altitude coastal and sub-coastal areas and extend inland for distance more than 100 km (62 mi) along river valleys and across watersheds. They are mostly to be found on the coasts of East Sumatra, Kalimantan (Central, East, South and West Kalimantan provinces), West Papua, Papua New Guinea, Brunei, Peninsular Malaya, Sabah, Sarawak, Southeast Thailand, and the Philippines (Riley et al.,1996). Indonesia has the largest area of tropical peatland. Of the total 440,000 km2 (170,000 sq mi) tropical peat swamp, about 210,000 km2 (81,000 sq mi) are located in Indonesia (Page, 2001; Wahyunto, 2006).
The Vasyugan Swamp is a large swamp in the western Siberia area of the Russian Federation. This is one of the largest swamps in the world, covering an area larger than Switzerland.
North America
The Atchafalaya Swamp at the lower end of the Mississippi River is the largest swamp in the United States. It is an important example of southern cypress swamp but it has been greatly altered by logging, drainage and levee construction. Other famous swamps in the United States are the forested portions of the Everglades, Okefenokee Swamp, Barley Barber Swamp, Great Cypress Swamp and the Great Dismal Swamp. The Okefenokee is located in extreme southeastern Georgia and extends slightly into northeastern Florida. The Great Cypress Swamp is mostly in Delaware but extends into Maryland on the Delmarva Peninsula. Point Lookout State Park on the southern tip of Maryland contains a large amount of swamps and marshes. The Great Dismal Swamp lies in extreme southeastern Virginia and extreme northeastern North Carolina. Both are National Wildlife Refuges. Another swamp area, Reelfoot Lake of extreme western Tennessee and Kentucky, was created by the 1811–12 New Madrid earthquakes. Caddo Lake, the Great Dismal and Reelfoot are swamps that are centered at large lakes. Swamps are often called bayous in the southeastern United States, especially in the Gulf Coast region.
List of major swamps
The world's largest wetlands include significant areas of swamp, such as in the Amazon and Congo River basins. Further north, however, the largest wetlands are bogs.