Wetlands improve water quality by filtering out pollutants, and reducing flood and storm damage by detaining water for short periods of time then releasing it slowly, minimizing erosion. They provide habitat for a diversity of plants and animals including many that are threatened and endangered. They protect lake and coastal shores by buffering the erosive action of waves. Wetlands benefit from forested buffers in the same ways other waterways benefit.
Four types of wetlands have been identified in Maryland. These are estuarine, palustrine, lacustrine, and riverine wetlands. Estuarine wetlands are deep-water tidal habitats with brackish, or slightly salty, water. Palustrine wetlands are nontidal and are dominated by trees, shrubs, persistent emergent plants, and emergent mosses and lichens. Lacustrine wetlands are found in depressions or dammed river channels with deep water and few plants. Generally, they are larger than 20 acres. Riverine wetlands are generally contained within a channel with water flowing periodically or continuously, or that connects two bodies of standing water.