Under the rules of the Clean Water Act, recent interpretation and changes to the act, and various state laws and regulations, wetlands that are destroyed due to development or agricultural purposes must be mitigated. Mitigation of wetlands means that wetlands that are lost must be replaced. Generally, mitigation must occur on site but it also can occur in areas away from where the wetlands were destroyed.

Mitigation generally involves restoration or creation of new wetlands, or in limites circumstances, the preservation of existing wetlands. The rules of mitigation vary by state. A common rule is that open-water wetlands are replaced at a 1:1 ratio (i.e., for every 1 acre destroyed, 1 acre needs to be replaced/created.) Wetlands with emergent vegetation are mitigated at a 1:2 ratio, and forested or shrubby wetlands are mitigated at a 1:3 ratio. For more information see the Wetland Permitting Process section and view this Environmental Protection Agency fact sheet.