Wetlands
Wetlands are ecosystems where water covers or saturates the soil for all or part of the year, shaping local soils, plants and wildlife. They range from marshes and swamps to peatlands, mangroves and tidal flats, and vary with water depth, timing, chemistry and landscape position. Wetlands support food webs and human communities through services that can include habitat, floodwater storage and water-quality functions. Their condition is strongly affected by changes in water flow and land use, making conservation and restoration important parts of environmental management.
Definition and boundaries
A wetland is an area in which water covers the soil, or lies at or near the surface, for long enough to shape its soils and the organisms able to live there. The wet period can be seasonal: a site may look dry during part of the year and still function as a wetland. The Ramsar Convention uses a deliberately broad definition that includes marshes, fens, peatlands and other water areas, whether natural or artificial and whether permanent or temporary. Scientific classification and legal definitions differ among countries, so a single test does not describe every wetland everywhere.
A diverse set of ecosystems
Wetlands occur inland and along coasts, in settings from river floodplains and lake margins to estuaries and shallow shorelines. Marshes are often dominated by soft-stemmed plants; swamps commonly have shrubs or trees; bogs and fens are peat-forming types whose water sources and chemistry differ. Coastal examples include salt marshes, mangrove swamps and seagrass beds. Classification systems group these habitats in different ways, but all emphasize the role of water: its source, movement, depth, duration and salinity influence soil formation and vegetation. Seasonal wetlands are not ecologically empty when dry; some provide essential breeding habitat during their wet phase.
Ecological and human importance
Wetland plants, microbes and animals form food webs that connect aquatic and terrestrial environments. Many species use wetlands for feeding, shelter or breeding, while coastal wetlands provide nursery habitat for fish and shellfish. Depending on local conditions and their position in a watershed, wetlands can retain floodwater, slow runoff, support water quality by trapping some sediment and nutrients, and help maintain surface-water flow during dry periods. Peatlands are especially important stores of carbon in waterlogged soils; draining or burning them can release some of that stored carbon. These functions vary among wetland types and sites, and wetlands work as part of larger watersheds rather than as isolated units.
Loss, pressures and conservation
Wetlands can be altered or lost when they are drained, filled, converted to agriculture or urban land, or cut off from their natural supply of water. Pollution and changes to river flow can also degrade habitats. The Convention on Wetlands' Global Wetland Outlook 2025 estimates that about 411 million hectares—roughly 22 percent of global wetland extent—have been lost since 1970; it presents this as an estimate of a complex global trend. The Convention on Wetlands, adopted in Ramsar, Iran, in 1971, provides a framework for designating Wetlands of International Importance, promoting the wise use of all wetlands and encouraging international cooperation. World Wetlands Day is observed each year on 2 February, the treaty's adoption date. Protection and restoration can help recover ecological functions, although results depend on the wetland and its wider watershed.
Key facts
- Defining feature
- Water is present at or near the soil surface long enough to shape wetland soils and biological communities; many wetlands are seasonal.
- Examples
- Marshes, swamps, bogs, fens, mangroves, tidal flats and other inland or coastal water habitats.
- International framework
- The Convention on Wetlands was adopted in Ramsar, Iran, in 1971 and is commonly called the Ramsar Convention.
- World Wetlands Day
- Observed annually on 2 February, the date the Convention on Wetlands was adopted.
- Estimated global loss
- The Global Wetland Outlook 2025 estimates that about 411 million hectares, or roughly 22% of global wetland extent, have been lost since 1970.
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Answers use only “Wetlands” and its references, with citations.
References
- 1.What is a Wetland?
U.S. Environmental Protection Agency · other · reliability: high · retrieved 15 October 2026
Supports: Defines wetlands through recurring or prolonged water presence, explains hydrology and soil, and describes inland and coastal settings.
- 2.What are wetlands?
The Convention on Wetlands (Ramsar Convention Secretariat) · other · reliability: high · retrieved 15 October 2026
Supports: Summarizes the Convention's broad definition of wetlands, including natural or artificial and permanent or temporary wetlands.
- 3.Classification and Types of Wetlands
U.S. Environmental Protection Agency · other · reliability: high · retrieved 15 October 2026
Supports: Explains wetland classification, types, hydrology, and examples of their ecological functions and pressures.
- 4.Why are Wetlands Important?
U.S. Environmental Protection Agency · other · reliability: high · retrieved 15 October 2026
Supports: Describes wetlands' role in habitats, food webs, floodwater storage and water quality.
- 5.Coastal Wetland Habitat
NOAA Fisheries, National Oceanic and Atmospheric Administration · other · reliability: high · retrieved 15 October 2026
Supports: Describes coastal wetland types, habitat functions and benefits to fisheries and communities.
- 6.Convention on Wetlands of International Importance especially as Waterfowl Habitat
UNESCO · other · reliability: high · retrieved 15 October 2026
Supports: Provides the treaty's adoption date, ecological and human benefits of wetlands, and the Convention's three pillars.
- 7.Peatlands store twice as much carbon as all the world's forests
United Nations Environment Programme · other · reliability: high · retrieved 15 October 2026
Supports: Explains peatlands' role as carbon stores and how drainage, agricultural conversion and burning can release stored greenhouse gases.
- 8.Global Wetland Outlook 2025
Scientific and Technical Review Panel of the Convention on Wetlands · other · reliability: high · retrieved 15 October 2026
Supports: Presents the 2025 global assessment and its estimate of wetland extent, loss and degradation.
- 9.Migratory species and wetlands: Insights from Global Wetland Outlook 2025
Convention on the Conservation of Migratory Species of Wild Animals (CMS), United Nations Environment Programme · other · reliability: high · retrieved 15 October 2026
Supports: Independently summarizes the 2025 estimate of global wetland loss since 1970.
- 10.World Wetlands Day
The Convention on Wetlands · other · reliability: high · retrieved 15 October 2026
Supports: States that World Wetlands Day is observed each year on 2 February, marking adoption of the Convention in 1971.
References are suggested by the research engine and may be incomplete. Unverified URLs are omitted rather than guessed.
Article history
- Version 115 October 2026 · EditorCreated by Zapia