A wetland is a landscape where water and land interact to create permanently or seasonally saturated soils and unique plant and animal communities. In studies of physical geography and environmental science, wetlands are treated as a distinct kind of environment and as a specific type of ecosystem that blends aquatic and terrestrial features.

Because wetlands contain both wet and dry microhabitats they often support a higher number of species than nearby uplands. They serve as critical habitat for birds, fish, amphibians, invertebrates and many plants, contributing substantially to regional biodiversity. This species richness makes some wetlands conservation priorities at national and global levels.

Types and characteristics

  • Marshes – shallow, frequently inundated areas dominated by herbaceous plants such as reeds and sedges.
  • Swamps – wetlands with standing water and abundant woody vegetation, including shrubs and trees.
  • Bogs – peat-accumulating wetlands, often acidic and dominated by mosses and specialized plants.
  • Fens – peat-forming but less acidic than bogs, with greater nutrient input and diverse sedge and grass communities.

Wetlands are distributed across many ecoregions and several globally important examples have been highlighted in conservation lists such as the Global 200.

Ecological functions and services

  • Water purification: wetlands filter sediments and absorb pollutants, improving downstream water quality.
  • Flood attenuation: they store excess water during heavy rains and release it slowly.
  • Carbon storage: peatlands and other wetlands sequester carbon, helping regulate climate.
  • Nursery habitat: many commercially important fish and shellfish spend juvenile stages in wetlands.

Because of these services, organizations such as the World Wide Fund for Nature emphasize wetland protection as part of broader conservation strategies.

Wetlands face threats from drainage for agriculture, urban development, pollution, invasive species and changing water regimes caused by climate change. International policy instruments and networks, notably the Ramsar Convention, encourage protection, wise use and restoration. Local restoration projects, protected-area designation and community management are common responses aimed at recovering lost functions and species.

Well-managed wetlands provide benefits for nature and people: they sustain fisheries, reduce flood risk, store carbon and support cultural values. Their complex hydrology and life forms make them both scientifically interesting and practically important in landscape planning and biodiversity conservation.