on
Stewart Island,
New Zealand Tidal flats, along with intertidal
salt marshes and
mangrove forests, are important
ecosystems. They support a large population of wildlife, and are a key habitat that allows tens of millions of migratory
shorebirds to migrate from breeding sites in the northern hemisphere to non-breeding areas in the southern hemisphere. They are often of vital importance to
migratory birds, as well as certain species of
crabs,
mollusks and
fish. In the
United Kingdom mudflats have been classified as a
Biodiversity Action Plan priority habitat. The maintenance of mudflats is important in preventing coastal erosion. However, mudflats worldwide are under threat from predicted
sea level rises, land claims for development,
dredging due to shipping purposes, and
chemical pollution. It is estimated that up to 16% of the world tidal flats have disappeared since the mid-1980s. The associated growth of coastal sediment deposits can be attributed to rates of subsidence along with rates of deposition (example: silt transported via river) and changes in sea level. Barren zones extend from the lowest portion of the intertidal zone to the marsh areas. Beginning in close proximity to the tidal bars, sand dominated layers are prominent and become increasingly muddy throughout the tidal channels. Common bedding types include laminated sand, ripple bedding, and bay mud.
Bioturbation also has a strong presence in barren zones.
Marshes contain an abundance of
herbaceous plants while the sediment layers consist of thin sand and mud layers.
Mudcracks are a common as well as wavy bedding planes. Marshes are also the origins of coal/peat layers because of the abundant decaying plant life.
Salt pans can be distinguished in that they contain thinly laminated layers of clayey silt. The main source of the silt comes from rivers. Dried up mud along with wind erosion forms silt dunes. When flooding, rain or tides come in, the dried sediment is then re-distributed. File:ISS013-E-75163 - View of Tunisia.jpg|alt=Satellite view of the Kneiss Islands, Tunisia|Satellite view of the
Kneiss Islands,
Tunisia. File:Skagit_Bay_6308.JPG|Gulls feeding on mudflats in
Skagit Bay,
Washington, United States Image:brewster mudflat.jpg|Mudflats in
Brewster, Massachusetts, United States, extending hundreds of yards offshore at the low tide. The line of
Wrack (seaweed) and seashells in the foreground indicates the
high-water mark. ==Cultural Services==