Salt marshes are coastal wetlands that are flooded and drained by tides. They grow in marshy soils composed of deep mud and peat. Peat is made of decomposing plant matter in layers several feet thick. Since salt marshes are often submerged by the tides and contain a lot of decomposing material, oxygen levels in the peat can be extremely low. These conditions give salt marshes their reputation for sometimes exuding a rotten-egg odor.
Although not always pleasing to our human sense of smell, salt marshes are the “ecological guardians of the coast” that maintain healthy fisheries, coastlines and communities. They provide shelter, food and nursery grounds for more than 75% of coastal fisheries species including shrimp, crab and many finfish. Salt marshes also protect shorelines from erosion by creating a buffer against wave action and by trapping soils. In flood prone areas, salt marshes reduce the flow of flood waters and absorb rainwater. By filtering runoff and excess nutrients, salt marshes also help to maintain water quality in coastal bays, sounds and estuaries. Salt marshes and other coastal wetlands also serve as “carbon sinks,” holding carbon that would otherwise be released into the atmosphere and contribute to climate change.
The U.S. has experienced tremendous losses of freshwater and coastal wetlands since the early 20th century, primarily from construction, development and habitat loss. The U.S. Fish and Wildlife Service estimated that between 2004 and 2009 alone, wetlands in coastal watersheds declined by 360,720 acres or over 80,000 acres per year. The National Park Service puts a high priority on wetland protection and restoration. Coastal parks have made great strides in restoring damaged wetlands and reclaiming their remarkable values for our coasts.