Mudflat

Mudflats or mud flats, also known as tidal flats or, in Ireland, slob or slobs,^[1][2] are coastal wetlands that form in intertidal areas where sediments have been deposited by tides or rivers. A global analysis published in 2019 suggested that tidal flat ecosystems are as extensive globally as mangroves, covering at least 127,921 km² (49,391 sq mi) of the Earth's surface.^[3] They are found in sheltered areas such as bays, bayous, lagoons, and estuaries; they are also seen in freshwater lakes and salty lakes (or inland seas) alike, wherein many rivers and creeks end. Mudflats may be viewed geologically as exposed layers of bay mud, resulting from deposition of estuarine silts, clays and aquatic animal detritus. Most of the sediment within a mudflat is within the intertidal zone, and thus the flat is submerged and exposed approximately twice daily.

A recent global remote sensing analysis estimated that approximately 50% of the global extent of tidal flats occurs within eight countries (Indonesia, China, Australia, United States, Canada, India, Brazil, and Myanmar) and that 44% of the world's tidal flats occur within Asia (56,051 km² or 21,641 sq mi).^[3] A 2022 analysis of tidal wetland losses and gains estimates that global tidal flats experienced losses of 7,000 km² (2,700 sq mi) between 1999 and 2019, which were largely offset by global gains of 6,700 km² (2,600 sq mi) over the same time period.^[4]

In the past tidal flats were considered unhealthy, economically unimportant areas and were often dredged and developed into agricultural land.^[5] Some mudflats can be extremely treacherous to walk on. For example, the mudflats surrounding Anchorage, Alaska, are made from fine glacial-silt which does not easily separate out its water, and, although seemingly solid, can quickly gel and become like quicksand when disturbed by stepping on it. Four people are known to have become stuck up to their waists and drowned when the tide came in, and many others are rescued from the Anchorage mudflats each year.^[6]

On the Baltic Sea coast of Germany in places, mudflats are exposed not by tidal action, but by wind-action driving water away from the shallows into the sea. This kind of wind-affected mudflat is called Windwatt in German.^{[citation needed]}