swamp, shallow body of water in a low-lying, poorly drained depression, usually containing abundant plant growth dominated by trees, such as cypress, and high shrubs. Swamps develop in moist climates, generally in such places as low-lying coastal plains, floodplains of rivers, and old lake basins or in areas where normal drainage has been disrupted by glacial deposits. In the United States, swamps cover approximately 100,000 sq mi (260,000 sq km), most of them occurring as small swamps in northeastern states that were covered with glaciers in the past. The most extensive swamps are found along the Atlantic and Gulf coastal plains, notable examples being the Everglades of S Florida, Dismal Swamp of Virginia, and Okefenokee Swamp of Georgia and N Florida. Because the bottom of a swamp is at or below the water table, swamps serve to channel runoff into the groundwater supply, thus helping to stabilize the water table. During periods of very heavy rains, a swamp can act as a natural flood control device, as excess runoff can be temporarily stored in its basin. Swamp vegetation varies with climate. Grasses, rushes, and sphagnum moss predominate in temperate climates; cypress and mangrove predominate in more tropical regions. Lush vegetation provides great protection for nesting waterfowl and fish as well as a hospitable habitat for many types of small mammal such as beaver and otter. Swamps that are drained make excellent agricultural land because of the high organic content of the bottom sediments. In addition, rising land values and demand have encouraged the drainage of many swamplands, such as coastal Florida, for home development. However, a problem associated with recently drained swamps is oxidation of the thick peat deposits forming the soil, which can result in subsidence of the land and such problems as cracked walls, broken underground pipes, and buckled roadways. The increased use of drained swampland for urban construction, with its associated acres of blacktop paving and storm sewers, results in greater runoff and increases the probability of flooding and pollution in these regions. Swamp drainage also destroys the nesting areas of many wildlife species. Thus, environmentalists have urged, with increasing success, the slowing down of swamp drainage. There are a variety of local terms for swamps, including bog, marsh, fen, and moor. However, bog usually refers to a swampy depression with a thick mat of living and dead organic matter floating on the water surface and a low level of oxygen in the water below. Marsh implies a large area of wet land where the dominant vegetation consists of low-lying grasses, rushes, and sedges.

or marsh gas

Organic compound, chemical formula CH₄, colourless, odourless gas that occurs in natural gas (called firedamp in coal mines) and from bacterial decomposition of vegetation in the absence of oxygen (including in the rumens of cattle and other ruminants and in the gut of termites). The simplest member of the paraffin hydrocarbons, methane burns readily, forming carbon dioxide and water if supplied with enough oxygen for complete combustion or carbon monoxide if the oxygen is insufficient. Mixtures of 5–14percnt methane in air are explosive and have caused many mine disasters. The chief source of methane is natural gas, but it can also be produced from coal. Abundant, cheap, and clean, methane is used widely as a fuel in homes, commercial establishments, and factories; as a safety measure, it is mixed with trace amounts of an odorant to allow its detection. It is also a raw material for many industrial materials, including fertilizers, explosives, chloroform, carbon tetrachloride, and carbon black, and is the principal source of methanol.

Learn more about methane with a free trial on Britannica.com.

Either of two large swamp trees (Taxodium distichum and T. ascendens; family Taxodiaceae) of the southern U.S. that are related to the sequoias. The hard red wood of cypress is often used for roofing shingles. The so-called deciduous cypress family (see deciduous tree) comprises 10 genera with 15 species of ornamental and timber evergreen trees, native to eastern Asia, Tasmania, and North America. The leaves on a single tree may be scalelike, needlelike, or a mixture of both. Both male and female cones are borne on the same tree. The Tasmanian cedar (Athrotaxis), Japanese cedar (Cryptomeria japonica), China fir (Cunninghamia lanceolata), umbrella pine (Sciadopitys verticillata), big tree, redwood, dawn redwood, and bald cypress are economically important timber trees in this family.

Learn more about bald cypress with a free trial on Britannica.com.

Freshwater wetland ecosystem characterized by poorly drained mineral soils and plant life dominated by trees. Swamps have a sufficient water supply to keep the ground waterlogged, and the water has a high-enough mineral content to stimulate decay of organisms and to prevent the accumulation of organic materials. They are found throughout the world. Seealso marsh.

Learn more about swamp with a free trial on Britannica.com.

Swamp and wildlife refuge, southeastern Georgia and northeastern Florida, U.S. It has an area of more than 600 sq mi (1,550 sq km). Located about 50 mi (80 km) inland from the Atlantic coast, it is bounded by the low, sandy Trail Ridge, which prevents direct drainage into the Atlantic. It has diverse and abundant wildlife. Exotic flowers, such as rare orchids, abound. In 1937 a large area of the swamp, almost all in Georgia, was made the Okefenokee National Wildlife Refuge.

Learn more about Okefenokee Swamp with a free trial on Britannica.com.

or Great Dismal Swamp

Wetland region, southeastern Virginia and northeastern North Carolina, U.S. Despite much lumbering and widespread destruction by fire, the area is still heavily wooded. About 30 mi (48 km) long and 10 mi (16 km) wide, it is home to many rare birds and numerous poisonous snakes. Noted for its fishing and hunting, it is traversed by the Dismal Swamp Canal, part of the Atlantic Intracoastal Waterway.

Learn more about Dismal Swamp with a free trial on Britannica.com.

A swamp is a wetland featuring temporary or permanent inundation of large areas of land, by shallow bodies of water. A swamp generally has a substantial number of hammocks, or dry-land protrusions, covered by aquatic vegetation, or vegetation that tolerates periodical inundation. The water of a swamp may be fresh water or salt water. A swamp is also generally defined as having no substantial peat deposits.

In North America, swamps are usually regarded as including a large amount of woody vegetation, but elsewhere this may not necessarily apply, such as in African swamps dominated by papyrus. By contrast a marsh in North America is a wetland without woody vegetation, or elsewhere, a wetland without woody vegetation which is shallower and has less open water surface than a swamp. A mire (or quagmire) is a low-lying wetland of deep, soft soil or mud that sinks underfoot.

Geology

Swamps are generally characterised by very slow-moving waters. They are usually associated with adjacent rivers or lakes. In some cases, rivers become swamps for a distance. Swamps are features of areas with very low topographic relief, although they may be surrounded by mountains.

Ecology

Swamps are characterised by rich biodiversity and specialized organisms such as frogs. For instance, southeastern U.S. swamps, such as those mentioned above, feature trees such as the Bald cypress and Water tupelo, which are adapted to growing in standing water, and animals such as the American alligator. A common species name in biological nomenclature is the Latin palustris, meaning "of the swamp". Examples of this are Quercus palustris (pin oak) and Thelypteris palustris (marsh fern).

Draining

Swamps were historically often drained to provide additional land for agriculture, and to reduce the threat of diseases born by swamp insects and similar animals. Swamps were generally seen as useless and even dangerous. This practice of swamp draining is nowadays seen as a destruction of a very valuable ecological habitat type of which large tracts have already disappeared in many countries.

Famous examples

In Iraq

The Tigris-Euphrates river system is a large swamp and river system in southern Iraq, inhabited in part by the Marsh Arabs. It was partly drained by Saddam Hussein in the 1990s in retaliation against the Shiite tribes' revolt against his dictatorship.

In the United States

The most famous swamps in the United States are the Everglades, Okefenokee Swamp and the Great Dismal Swamp. The Okefenokee is located in extreme southeastern Georgia and extends slightly into northeastern Florida. 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, was created by the New Madrid earthquake of 1812. 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.

Heraldry

A swamp appears in the coat of arms of Gesturi, Italy.

List of major swamps

Africa

• Bangweulu Swamps, Zambia
• Okavango Swamp, Botswana
• Sudd, Sudan
• Niger Delta, Nigeria

Asia

• Asmat Swamp, Indonesia
• Vasyugan Swamp, Russia

North America

• Atchafalaya National Wildlife Refuge, Louisiana, United States
• Big Cypress National Preserve, Florida, United States
• Great Black Swamp, Indiana/Ohio, United States
• Great Cypress Swamp, Maryland, United States, also known as Great Pocomoke Swamp
• Great Dismal Swamp, North Carolina/Virginia, United States
• Great Swamp National Wildlife Refuge, New Jersey, United States
• Honey Island Swamp, Louisiana, United States
• Limberlost, Indiana, United States
• Louisiana swamplands, Louisiana, United States
• Okefenokee Swamp, Georgia/Florida, United States
• Reelfoot Lake, Tennessee, United States
• Everglades, Florida, United States

South America

• Lahuen Ñadi, Chile
• Pantanal, Brazil
• Paraná Delta, Argentina

See also

Aquatic plant Bog Hydrogen sulfide Marsh		Marsh gas Muck Peat Salt marsh		Slough Wetland Will o' the wisp

References