A wetland is a complex ecosystem distinguished by soil that is flooded or saturated. These conditions result in low-oxygen environments that promote specific kinds of animals , microbes , and plants . Wetlands serve as transition zones between terrestrial and aquatic systems, and they have significant implications for various species. They sustain human communities by acting as habitats, providing food, and offering economically valuable sport fishing, hunting, and recreational opportunities.

Where are wetlands usually found?

Wetlands exist worldwide, across all biomes, with a higher concentration in boreal and tropical regions, and a wide distribution of inland and coastal wetlands in temperate zones. They can be found in various locations, such as the prairie potholes of North America, the Mesopotamian marshlands at the joining of the Tigris and Euphrates rivers, and the bog-and-fen mosaic of the taiga. Wetlands are common at river mouths, especially those with extensive deltas, and in low-lying areas with poor drainage at the heads of drainage patterns. They can also be located in basinlike depressions and along mature river valleys with floodplains slightly elevated above river level. Salt marshes are common along the east coast of the United States, in the Arctic, northern Europe, Australia, and New Zealand.

What types of plants and animals live in wetlands?

Wetlands are unique ecosystems that support a diverse range of plant and animal life. These areas form transition zones between terrestrial and aquatic systems, leading to high biodiversity. Wetland plants include grasses, sedges, reeds, and rushes. Wild rice is also a commercially important marsh plant. Wetlands provide habitats for various animal species, including waterfowl, fish, and other organisms. The Everglades are home to endangered species like the manatee, Florida panther, wood stork, and American crocodile. Many serve as bird sanctuaries.

How do wetlands help the environment?

Wetlands play a vital role in the health of the environment. Acting as transition zones between terrestrial and aquatic systems, wetlands support high levels of biodiversity , offering habitats for diverse species and serving as refuges for rare and endangered ones. They are key players in nutrient cycling , improve water quality, protect shorelines, recharge groundwater, minimize flood risks, and store atmospheric carbon, helping to fight global warming . Because of their ecological importance, wetland preservation and restoration is a key strategy in the fight against water scarcity.

What are the main types of wetlands?

Wetlands are classified using various systems based on factors such as hydrology, structure, and function. Common wetland types include: Marshes These are nonforested freshwater systems, often near rivers and dominated by grasses and grass-like plants. Swamps Swamps are defined by their poor drainage, mineral soils, and tree-dominated plant life. Bogs Bogs are peat-rich, poorly drained ecosystems usually found in cool regions. They are divided into three types: typical bogs, pocosins, and tropical bogs. Fens These are low-lying areas covered with water and dominated by grasses. Fens have a pH above 5 because of the flow of water through them. Mangrove swamps These brackish-water coastal swamps in tropical and subtropical areas are typically dominated by shrubby halophytes and are partly inundated by tidal flow.

How do humans impact and protect wetlands?

Humans impact wetlands through draining, filling, and construction, leading to habitat loss and reduced biodiversity. Activities like logging, mining, and fire suppression further disrupt wetland ecosystems. Pollution from agricultural chemicals and the introduction of invasive species also degrade these environments. Climate change accelerates these threats, altering water cycles and potentially drying out wetlands, while also releasing greenhouse gasses from peatlands. Recognizing their importance, conservation efforts include local, national, and international policies such as the Ramsar Convention and the North American Waterfowl Management Plan , which aim to protect wetland habitats and migratory birdlife. Sustainable practices prioritize wetland restoration and conservation to maintain their ecological functions, including water purification, flood control, and carbon storage.

Wetland

Images & Videos

Bald cypress trees with wide, flared trunks stand in still, shallow water in a Louisiana swamp, their green foliage creating a dense canopy.

At a Glance

wetland summary

Wetland

ecosystem

Written by

Caren J. Crandell

Fact-checked by

Britannica Editors

Last updated

Nov. 12, 2026 •History

Top Questions

What is a wetland?
A wetland is a complex ecosystem distinguished by soil that is flooded or saturated. These conditions result in low-oxygen environments that promote specific kinds of animals, microbes, and plants.

Wetlands serve as transition zones between terrestrial and aquatic systems, and they have significant implications for various species. They sustain human communities by acting as habitats, providing food, and offering economically valuable sport fishing, hunting, and recreational opportunities.
1 Britannica Source
1. wetland
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Where are wetlands usually found?
Wetlands exist worldwide, across all biomes, with a higher concentration in boreal and tropical regions, and a wide distribution of inland and coastal wetlands in temperate zones. They can be found in various locations, such as the prairie potholes of North America, the Mesopotamian marshlands at the joining of the Tigris and Euphrates rivers, and the bog-and-fen mosaic of the taiga.

Wetlands are common at river mouths, especially those with extensive deltas, and in low-lying areas with poor drainage at the heads of drainage patterns. They can also be located in basinlike depressions and along mature river valleys with floodplains slightly elevated above river level. Salt marshes are common along the east coast of the United States, in the Arctic, northern Europe, Australia, and New Zealand.
3 Britannica Sources
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What types of plants and animals live in wetlands?
Wetlands are unique ecosystems that support a diverse range of plant and animal life. These areas form transition zones between terrestrial and aquatic systems, leading to high biodiversity.

Wetland plants include grasses, sedges, reeds, and rushes. Wild rice is also a commercially important marsh plant.

Wetlands provide habitats for various animal species, including waterfowl, fish, and other organisms. The Everglades are home to endangered species like the manatee, Florida panther, wood stork, and American crocodile. Many serve as bird sanctuaries.
3 Britannica Sources
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How do wetlands help the environment?
Wetlands play a vital role in the health of the environment. Acting as transition zones between terrestrial and aquatic systems, wetlands support high levels of biodiversity, offering habitats for diverse species and serving as refuges for rare and endangered ones. They are key players in nutrient cycling, improve water quality, protect shorelines, recharge groundwater, minimize flood risks, and store atmospheric carbon, helping to fight global warming. Because of their ecological importance, wetland preservation and restoration is a key strategy in the fight against water scarcity.
2 Britannica Sources
1. peat
2. wetland: Wetland functions and ecosystem benefits
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
What are the main types of wetlands?
Wetlands are classified using various systems based on factors such as hydrology, structure, and function. Common wetland types include:
- Marshes These are nonforested freshwater systems, often near rivers and dominated by grasses and grass-like plants.
- Swamps Swamps are defined by their poor drainage, mineral soils, and tree-dominated plant life.
- Bogs Bogs are peat-rich, poorly drained ecosystems usually found in cool regions. They are divided into three types: typical bogs, pocosins, and tropical bogs.
- Fens These are low-lying areas covered with water and dominated by grasses. Fens have a pH above 5 because of the flow of water through them.
- Mangrove swamps These brackish-water coastal swamps in tropical and subtropical areas are typically dominated by shrubby halophytes and are partly inundated by tidal flow.
6 Britannica Sources
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
How do humans impact and protect wetlands?
Humans impact wetlands through draining, filling, and construction, leading to habitat loss and reduced biodiversity. Activities like logging, mining, and fire suppression further disrupt wetland ecosystems. Pollution from agricultural chemicals and the introduction of invasive species also degrade these environments. Climate change accelerates these threats, altering water cycles and potentially drying out wetlands, while also releasing greenhouse gasses from peatlands.

Recognizing their importance, conservation efforts include local, national, and international policies such as the Ramsar Convention and the North American Waterfowl Management Plan, which aim to protect wetland habitats and migratory birdlife. Sustainable practices prioritize wetland restoration and conservation to maintain their ecological functions, including water purification, flood control, and carbon storage.
1 Britannica Source
1. wetland: Wetland management
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Wetland, complex ecosystem characterized by flooding or saturation of the soil, which creates low-oxygen environments that favor a specialized assemblage of plants, animals, and microbes. These organisms exhibit adaptations designed to tolerate periods of sluggishly moving or standing water. Wetlands are usually classified according to soil and plant life as bogs, marshes, swamps, and other, similar environments.

Wetlands and the subdiscipline of wetland ecology are a relatively new area of study in the field of ecology, primarily arising out of the laws and other regulations enacted during the 1970s. The term wetland, however, was first used formally in 1953, in a report by the U.S. Fish and Wildlife Service (USFWS) that provided a framework for a later publication concerning waterfowl habitat in the United States. Since then, wetlands have been variously defined by ecologists and government officials. No single, formal definition exists; however, the definition provided by the Ramsar Convention, an intergovernmental treaty signed in Ramsar, Iran, in 1971 to guide national and international wetland-conservation measures, is among the most widely referenced:

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.

This definition is also broad enough to encompass open water used by birds—the concept that originally inspired the protection of wetlands and associated aquatic sites.