Wetland
Land where water strongly influences soils and ecological conditions, permanently or seasonally.
Example
Marshes and swamps can support biodiversity and regulate water flows.
The catch
Some wetlands emit methane naturally; their full climate role needs careful assessment.
Related terms
Biodiversity, Methane, Afforestation, Blue carbon, Carbon sink, Carbon stock
In more depth
Wetland, explained.
Wetlands are the largest natural source of methane and hold some of the densest carbon stores on land. Freshwater marshes and swamps produce methane in waterlogged, oxygen-poor soils. Coastal wetlands such as mangroves and salt marshes emit far less, because sulphate in seawater suppresses methane-producing microbes, which helps explain why they anchor discussions of blue carbon.
Draining a peat-forming wetland turns a long-term carbon store into a source. Restoring a wetland is often a nature-based solution for flood control as well. Assess a project by its net balance of CO₂ and methane over time, measured on site where possible.