Journal of Marine Science: Research & Development
Open Access

A wetland is a distinct ecosystem that is flooded by water, either permanently or seasonally, where oxygen-free processes prevail. The primary factor that distinguishes wetlands from other landforms or water bodies is the characteristic vegetation of aquatic plants, adapted to the unique hydric soil. Wetlands play several functions, including water purification, water storage, processing of carbon and other nutrients, stabilization of shorelines, and support of plants and animals.[4] Wetlands are also considered the most biologically diverse of all ecosystems, serving as home to a wide range of plant and animal life. Whether any individual wetland performs these functions, and the degree to which it performs them, depends on characteristics of that wetland and the lands and waters near it.[5] Methods for rapidly assessing these functions, wetland ecological health, and general wetland condition have been developed in many regions and have contributed to wetland conservation partly by raising public awareness of the functions and the ecosystem services some wetlands provide.

Wetlands occur naturally on every continent. The water in wetlands is either freshwater, brackish, or saltwater. The main wetland types are swamp, marsh, bog, and fen; sub-types include mangrove forest, carr, pocosin, floodplains, mire, vernal pool, sink, and many others. Many peatlands are wetlands. Wetlands can be tidal (inundated by tides) or non-tidal. The largest wetlands include the Amazon River basin, the West Siberian Plain, the Pantanal in South America, and the Sundarbans in the Ganges-Brahmaputra delta. A baygall is another type of wetland found in the forest of the Gulf Coast states in the USA.

A wetland is an area of land that is either covered with water or saturated with water. Unique plants, called hydrophytes, define wetland ecosystems. This wooded wetland, near the Stillaguamish River in Washington, is dominated by western skunk cabbages, also called "swamp lanterns." The UN Millennium Ecosystem Assessment determined that environmental degradation is more prominent within wetland systems than any other ecosystem on Earth. Constructed wetlands are used to treat municipal and industrial wastewater as well as stormwater runoff. They may also play a role in water-sensitive urban design.

Estuarine marshes commonly called “salt and brackish marshes” are tidal wetlands associated with the world’s estuaries where salinities range from well above sea strength to nearly freshwater. Subject to frequent tidal flooding, plant communities are dominated by halophytic (salt-tolerant) herbs, subshrubs, and/or succulent-leaved shrubs. Not uniformly distributed along the world’s sea coasts, tidal marshes tend to be the dominant plant community of the intertidal zone at middle and higher latitudes. The global extent of estuarine marshes is not well documented, and this contributes to conservative estimates of their soil carbon stores.

Most regions report significant historical and on-going loss of estuarine marshes by human developments that in-part reflect a shift from an agrarian to industrial society and natural events. Economic and cultural values set by society determine how estuarine marshes functions that yield many benefits to people and the estuarine aquatic ecosystem are valued. Estuarine marshes are increasingly being recognized among the world’s most valuable ecosystems and given their location between land and the sea, are especially vulnerable to human development and the effects of climate change.