Wetland
Semi-aquatic ecosystems flooded or saturated with water.
A wetland is a distinct semi-aquatic ecosystem whose groundcovers are flooded or saturated in water, either permanently, for years or decades, or only seasonally. Flooding results in oxygen-poor (anoxic) processes taking place, especially in the soils. Wetlands form a transitional zone between waterbodies and dry lands, and are different from other terrestrial or aquatic ecosystems due to their vegetation's roots having adapted to oxygen-poor waterlogged soils. They are considered among the most biologically diverse of all ecosystems, serving as habitats to a wide range of aquatic and semi-aquatic plants and animals, with often improved water quality due to plant removal of excess nutrients such as nitrates and phosphorus.
- type
- Ecosystem
- distribution
- Every continent except Antarctica
- water_types
- Freshwater, brackish, or saltwater
- major_types
- Marsh, swamp, bog, fen, mangrove forest
- largest_examples
- Amazon River basin, West Siberian Plain, Pantanal, Sundarbans
Lore & Background
Wetlands exist on every continent except Antarctica. The water in wetlands is either freshwater, brackish or saltwater. Common types of wetlands are described based on the dominant plants and the source of the water. For example, marshes are wetlands dominated by emergent herbaceous vegetation such as reeds, cattails, and sedges. Swamps are dominated by woody vegetation, such as trees and shrubs (although reed swamps in Europe are dominated by reeds, not trees). Mangrove forests are wetlands with mangroves and halophytic woody plants that have evolved to tolerate salty water.
Reader's Guide
Wetlands contribute many ecosystem services that benefit people. These include water purification, stabilization of shorelines, storm protection and flood control. In addition, wetlands also process and condense carbon (in processes called carbon fixation and sequestration), and other nutrients and water pollutants. Wetlands can act as a sink or a source of carbon, depending on the specific wetland. If they function as a carbon sink, they can help with climate change mitigation. However, wetlands can also be a significant source of methane emissions due to anaerobic decomposition of soaked detritus, and some are also emitters of nitrous oxide. Humans are disturbing and damaging wetlands in many ways, including oil and gas extraction, building infrastructure, overgrazing of livestock, overfishing, alteration of wetlands including dredging and draining, nutrient pollution, and water pollution. Methods exist for assessing wetland ecological health. These methods have contributed to wetland conservation by raising public awareness of the functions that wetlands can provide.
Did You Know?
- Wetlands exist on every continent except Antarctica.
- The world's largest wetlands include the Amazon River basin, the West Siberian Plain, the Pantanal, and the Sundarbans.
- Wetlands can be a significant source of methane emissions due to anaerobic decomposition of soaked detritus.
Frequently Asked Questions
What is a wetland in geomorphology?
A wetland is a semi-aquatic ecosystem in which the ground is flooded or water-saturated either permanently, seasonally, or for stretches of years to decades. That persistent saturation drives oxygen-poor (anoxic) chemical processes in the soils, distinguishing wetlands from both fully aquatic and fully terrestrial settings.
What are the main types of wetlands?
The five principal categories are marsh, swamp, bog, fen, and mangrove forest. Depending on their setting, a wetland may hold freshwater, brackish water, or saltwater.
Where are wetlands found, and what are the largest examples?
Wetlands occur on every continent except Antarctica. Among the biggest examples are the Amazon River basin, the West Siberian Plain, the Pantanal, and the Sundarbans.
What makes wetlands ecologically unique compared to other ecosystems?
Wetlands occupy a transitional zone between open waterbodies and dry land, and their plant roots are specifically adapted to survive in oxygen-poor, waterlogged soils. They are considered among the most biologically diverse ecosystems on Earth, sheltering a broad range of aquatic and semi-aquatic organisms.
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