Mudflats are areas where sedimentation has occurred due to the decreasing energy of the river as it reaches its mouth. The sediment is silt or clay based and has a high organic content. Mudflats dissipate wave energy very effectively and therefore are an excellent tidal defense against eroding saltmarsh, damaging coastal defenses and flooding low-lying land. Mudflats may also be important for pollution sequestration, as the organic material draws in pollutants and they may therefore contain large concentrations of heavy metals. Mudflats have high biological productivity but low diversity. The JNCC Marine Nature Conservation Review (MNCR) biotope codes for mudflats are LMU.SMu (Sandy mud shores), LMU.Mu (Soft mud shores) and LMS.MS (Muddy sand shores). In areas of low salinity the characteristic species would include the Common Cockle Cerastoderma edule, Sand-hopper Corophium volutator, Laver Spire Shell Hydrobia ulvae, Ragworm Hediste diversicolor and Oligochaete Annelids (principally Tubificoides spp). With a slight increase in salinity, the polychaetes Catworm Nephtys hombergi and Lugworm Arenicola marina occur. In areas with slightly larger particles, Seagrass (Zostera spp.) beds may develop. Where stones and shells provide an initial attachment for byssus threads (strong silky threads which some molluscs use to attach themselves to a substrate), beds of the Common Mussel Mytilus edulis occur. The surface of the sediment on mudflats is often apparently devoid of vegetation, although mats of microalgae are common, which bind the sediment.

There are several threats currently affecting or which may affect mudflats in the future. Rising sea levels threaten to submerge large areas of mudflats, the UK BAP currently estimates that 8000 to 10,000 hectares of intertidal flats will be lost in England between 1993 and 2013. They predict much of the loss to be in southern and south-east England. One of the major threats is land reclamation, which has removed about 25% of Great Britain estuarine intertidal flats (and up to 80% in some estuaries), according to the UK BAP. Loss of mudflats may also influence other estuary habitats such as saltmarsh. Another large threat is diffuse and point source discharges from agriculture, industry and urban areas can create abiotic areas or produce algal mats which may affect invertebrate communities. Modification of mudflats such as oil and gas extraction and dredging for navigation have important effects on the biology of in sediments and on sediment supply and transport and human disturbance affects bird populations roosting and feeding in the area also. Finally, higher sea levels and more frequent storms resulting from climate change may affect the sedimentation patterns of mudflats and estuaries.

Mudflats are protected by several different international and EU agreements which are implemented through relevant UK enabling legislation. In addition to this international protection, UK legislation protects mudflats either directly or through by controlling water quality. The international designations of significance to mudflats are the Ramsar Convention protecting wetlands of international importance, the Bonn Convention to protect migratory species and the Bern Convention to conserve European wildlife and habitats. Sites designated under EU law form part of the Natura 2000 series of protected sites, i.e. Special Protected Areas (SPAs) under the EC Birds Directive or Special Areas of Conservation (SACs) under the 1992 EC Habitats Directive. Under the Wildlife and Countryside Act 1981, there are Sites of Special Scientific Interest (SSSIs) and Areas of Special Scientific Interest (ASSIs) in Northern Ireland that are designated for their mudflats.

Several measures have been carried out in order to conserve this habitat such as research on coastal and estuarine processes and an EU Marine Science and Technology (MAST) study of mudflat physical and biological processes and interactions.

The UK BAP objectives for mudflats are to maintain the present extent and regional distribution of mudflats, taking into account and compensating for any losses there may be through development, create and/or restore enough intertidal area to offset any losses due to rising sea levels in the next 50 years and to restore estuarine water quality to ensure existing mudflats fulfil their important ecological role. These objectives will be met through various actions through lead agencies which include:

• Monitor the implementation of strong development control policies to prevent development in flood risk areas with the objective of retaining the option to use such areas for the restoration of intertidal flats if required.
• Strengthen development and coastal protection planning policy to ensure where possible the maintenance of all active sediment sources that supply intertidal flats.
• Develop policies to use soft dredged material from estuaries to create mudflats elsewhere (in the same estuary where possible).
• Apply appropriate conservation designations to all intertidal areas that meet national and international criteria for site section and ensure appropriate management of designated sites.
• Ensure that wherever practicable coastal defense or other construction works avoid disruption of coastal processes that might lead to a loss of, or damage to, mudflats.
• Maintain and where possible improve estuarine and coastal water quality.
• Ensure that good-practice guidance is available to shoreline management authorities on how to plan for the maintenance of mudflats in a period of rising sea level. Particular attention should be given to the use of dredged material for this purpose and the creation of new mudflats.
• Ensure that relevant European statutes and international conventions provide adequate protection for mudflats.
• Run field trials to refine and demonstrate techniques for habitat restoration and creation. Particular attention should be given to the use of dredged material for this purpose.
• Continue to develop an understanding of the value of mudflats for flood and coastal defense and the holistic management of these habitats in conjunction with flood risk management.
• Initiate research into sediment exchange processes between mudflats and other coastal habitats and on the dynamics of cohesive sediments in estuaries.
• Raise public awareness of the ecological and socio-economic value of mudflats.