Wetlands are areas where water covers the soil or is present at or near the surface for significant portions of the year. Marshes, swamps, bogs, and mangroves are all types of wetlands. Though they occupy only about six percent of Earth's land surface, wetlands provide ecological services far out of proportion to their size, earning them the nickname "the kidneys of the landscape."
How Wetlands Filter Water
Wetlands act as natural water treatment systems. As water flows slowly through a wetland, plants, soils, and microorganisms remove pollutants, sediment, and excess nutrients. Wetland plants absorb nitrogen and phosphorus from agricultural runoff that would otherwise cause harmful algal blooms in rivers and coastal waters. The dense vegetation also traps sediment, preventing it from reaching downstream waterways.
Carbon Storage
Wetlands, particularly peatlands, are massive carbon stores. Although peatlands cover only three percent of the global land area, they store approximately twice as much carbon as all the world's forests combined. When wetlands are drained or degraded, this stored carbon is released as carbon dioxide, contributing significantly to climate change.
Types of Wetlands
Wetlands vary enormously depending on their water source, soil type, and vegetation. Each type provides distinct ecological benefits and supports different communities of life.
- Marshes — Dominated by grasses and reeds, often found along rivers and lakes, teeming with birds and amphibians
- Swamps — Forested wetlands with standing water, home to species like cypress trees, alligators, and herons
- Bogs — Acidic peatlands fed primarily by rainfall, with unique plant communities including carnivorous sundews
- Mangroves — Coastal forests adapted to saltwater that protect shorelines from storms and serve as nurseries for marine life
Threats to Wetlands
Despite their immense value, wetlands have been drained and destroyed at an alarming rate. Since 1700, an estimated 87 percent of the world's wetlands have been lost, primarily to agriculture and urban development. Remaining wetlands face threats from pollution, water diversion, and climate change.
Restoring and protecting wetlands is one of the most cost-effective strategies for improving water quality, reducing flood damage, storing carbon, and preserving biodiversity. Every dollar invested in wetland conservation returns many times its value in ecosystem services.