Salt marsh (coastal wetland)

Characteristics and vegetation

Salt marshes are characterized by fine sediments, gentle tidal exchange, and a mix of saline and brackish conditions. Plants that tolerate salt and waterlogging—so-called halophytes—dominate the landscape. Typical vegetation includes grasses and low herbs that trap sediment and build elevation over time. These plants create a distinctive zonation from lower tidal channels to higher marsh platforms where different species tolerate different inundation levels.

Ecology and key functions

Salt marshes support diverse communities of invertebrates, fish and birds and function as productive coastal habitats. They act as nurseries for juvenile fish and provide feeding and nesting grounds for migratory birds. Many species of animals rely on marshes during part of their life cycles. Salt marshes also perform vital ecosystem services that benefit humans and wildlife alike:

• Flood and storm protection by absorbing wave energy and storing water.
• Water filtration through trapping of sediments and uptake of nutrients.
• Carbon storage in deep organic soils, helping mitigate climate change.

These attributes make them valuable habitats for conservation and coastal management.

Formation, history and threats

Salt marshes develop where sediment accumulation and salt-tolerant vegetation allow land to build upward in response to regular tidal flooding. Over centuries many marshes have shifted with sea-level change and human alteration of coasts. Today they face threats from coastal development, pollution, invasive species and accelerated sea-level rise. Management approaches include protected areas, restoration of tidal flow and sediment replenishment to preserve their ecological functions.

Salt marshes are distinct from mangrove forests (typically tropical, with woody trees) and from freshwater marshes (which lack regular saline inundation), but all are important types of wetlands that support biodiversity and provide natural coastal resilience.