Purpose and scope

Seabed habitats and the communities of species that occupy them are an essential component of the marine ecosystem and our overall understanding of ecosystem function must relate seabed habitats to hydrography, nutrient cycling, plankton changes and the distribution of wide-ranging species (i.e. fish stocks, marine mammals, birds). A greater understanding of the distribution, extent and status or quality of marine habitats is required to facilitate the protection of threatened and rare habitats and, more generally, the assessment of the state of the marine environment. Such information is also needed to improve spatial and strategic planning of human activities, in particular to promote the wiser use of habitats where there are competing demands (e.g. fishing, sand and gravel extraction, wind energy generation, nature conservation). As such, information on marine habitats needs to play a major role in the ecosystem-based approach to management of the marine environment that is now widely advocated at national and international levels (Defra 2002; North Sea Conference 2002).
This habitat classification has, consequently, been developed as a tool to aid the management and conservation of marine habitats. It provides an ecologically-based classification of seashore and seabed features, aimed primarily at classifying benthic communities of invertebrates and seaweeds in a way which is meaningful both to detailed scientific application and to the much broader requirements for management of the marine environment. The classification is relevant to the habitat requirements of more mobile species, such as fish and marine mammals, but these are not its primary focus. Whilst the corresponding European EUNIS classification also includes water column (plankton) habitats, this aspect has not yet been developed here.
The classification aims to provide comprehensive coverage, by including habitats for artificial, polluted or barren areas as well as more natural habitats, which encompass:
1.   Marine, estuarine and brackish-water (lagoon) habitats - It also includes reference to saltmarsh habitats described in the National Vegetation Classification (NVC) (Rodwell 2000; Doody, Johnston & Smith 1993) as these are regularly covered by the sea, and NVC types which occur in brackish lagoons (Rodwell 1995).
2.   Rock and sediment habitats.
3.   Upper shore to coastal waters - From the supralittoral or splash zone and strand-line on the shore out to the 200 nm limit. The habitats beyond the near-shore subtidal zone (about the 3 mile/5 km limit) and below about 50 m depth are less well described here, due to more limited availability of data; more types will be defined as data become available.
4.   Plant and animal communities, including epibiota and infauna - Types are defined using both their fauna and flora. Most benthic marine habitats include sedentary animals and small mobile animals which are an integral part of the community, whilst in many habitats, especially in deeper water, there are no plants (seaweeds or marine angiosperms) to characterise the habitats. Sediment types are defined both by their epibiota (surface-dwelling animals and plants) and their infauna (animals living in the sediment).
5.   Britain and Ireland - It covers habitats throughout Britain and Ireland and, through a widely-accepted broad framework, is readily expandable to include offshore continental shelf habitats and other areas in the north-east Atlantic, Mediterranean and Baltic Seas. This is being achieved through the EUNIS classification.