Saltmarsh
A saltmarsh (also salt marsh) is a coastal wetland that is flooded and drained by salt water brought in by the tides.[1] Saltmarshes occur around the world, especially in middle to high latitudes, and are a common habitat in estuaries.[2] In the United Kingdom, according to the Joint Nature Conservation Committee (JNCC), coastal saltmarshes are the upper parts of intertidal mudflats that have plants growing on them, lying roughly between the levels reached by the lowest and the highest high tides. In Scotland they are also known as merse.[3]
Where saltmarshes form
Saltmarshes usually form in fairly sheltered places. The JNCC lists five main kinds of setting in the UK: estuaries, saline lagoons, behind barrier islands, at the heads of sea lochs, and on beach plains.[4]
Plants
Only a small number of plant species can live in a saltmarsh. They are halophytes, which means they can tolerate salt, and they are adapted to being covered by the tides regularly.[5] The plants grow in bands, or zones, depending on how often the tide reaches them. At the lowest level, pioneer plants called glassworts (Salicornia) can survive being covered by as many as 600 tides a year, while plants of the upper marsh can survive only occasional flooding.[6]
Wildlife
Saltmarshes are important for wading birds and wildfowl. Birds that feed on nearby mudflats shelter there at high tide; waders, gulls and terns nest there; and small perching birds find food there, especially in autumn and winter.[7] Saltmarshes also give young fish a sheltered place to grow.[8]
Loss and conservation
Coastal saltmarsh is a priority habitat in the UK Biodiversity Action Plan; the JNCC's 2011 description was adapted from the 1994 action plan for the habitat.[9] The JNCC says that since medieval times many saltmarshes have become smaller because land was claimed from them, and that this continued until quite recently: for example, 858 hectares of saltmarsh in the Wash were turned into farmland between 1970 and 1980.[10]
References
- ↑ "What is a salt marsh?". National Ocean Service, National Oceanic and Atmospheric Administration. Retrieved 20 October 2026.
Salt marshes are coastal wetlands that are flooded and drained by salt water brought in by the tides.
- ↑ "What is a salt marsh?". National Ocean Service, National Oceanic and Atmospheric Administration. Retrieved 20 October 2026.
Salt marshes occur worldwide, particularly in middle to high latitudes. Thriving along protected shorelines, they are a common habitat in estuaries.
- ↑ UK Biodiversity Action Plan Priority Habitat Descriptions: Coastal Saltmarsh (PDF) (Report). Joint Nature Conservation Committee. 2011. Retrieved 20 October 2026.
Coastal saltmarshes in the UK (also known as 'merse' in Scotland) comprise the upper, vegetated portions of intertidal mudflats, lying approximately between mean high water neap tides and mean high water spring tides.
- ↑ UK Biodiversity Action Plan Priority Habitat Descriptions: Coastal Saltmarsh (PDF) (Report). Joint Nature Conservation Committee. 2011. Retrieved 20 October 2026.
Saltmarshes are usually restricted to comparatively sheltered locations in five main physiographic situations: in estuaries, in saline lagoons, behind barrier islands, at the heads of sea lochs, and on beach plains.
- ↑ UK Biodiversity Action Plan Priority Habitat Descriptions: Coastal Saltmarsh (PDF) (Report). Joint Nature Conservation Committee. 2011. Retrieved 20 October 2026.
Saltmarsh vegetation consists of a limited number of halophytic (salt tolerant) species adapted to regular immersion by the tides.
- ↑ UK Biodiversity Action Plan Priority Habitat Descriptions: Coastal Saltmarsh (PDF) (Report). Joint Nature Conservation Committee. 2011. Retrieved 20 October 2026.
At the lowest level the pioneer glassworts Salicornia spp can withstand immersion by as many as 600 tides per year, while transitional species of the upper marsh can only withstand occasional inundation.
- ↑ UK Biodiversity Action Plan Priority Habitat Descriptions: Coastal Saltmarsh (PDF) (Report). Joint Nature Conservation Committee. 2011. Retrieved 20 October 2026.
Saltmarshes are an important resource for wading birds and wildfowl. They act as high tide refuges for birds feeding on adjacent mudflats, as breeding sites for waders, gulls and terns and as a source of food for passerine birds particularly in autumn and winter.
- ↑ UK Biodiversity Action Plan Priority Habitat Descriptions: Coastal Saltmarsh (PDF) (Report). Joint Nature Conservation Committee. 2011. Retrieved 20 October 2026.
Saltmarshes also provide sheltered nursery sites for several species of fish.
- ↑ UK Biodiversity Action Plan Priority Habitat Descriptions: Coastal Saltmarsh (PDF) (Report). Joint Nature Conservation Committee. 2011. Retrieved 20 October 2026.
This habitat description has been adapted from the 1994 UK BAP Action Plan for Coastal saltmarsh beds and would benefit from an update.
- ↑ UK Biodiversity Action Plan Priority Habitat Descriptions: Coastal Saltmarsh (PDF) (Report). Joint Nature Conservation Committee. 2011. Retrieved 20 October 2026.
Since medieval times, many saltmarshes have been reduced in extent by land claim. This practice continued until very recently; for instance, in the Wash 858 ha of saltmarsh were converted to agricultural use between 1970 and 1980.