| A series of terms are being developed in the UK that express national importance of marine landscapes, habitats and species according to quantitative criteria (Lieberknecht et al., 2003). Assessment is also dependent on scientific judgement regarding natural abundance, range or extent and the adequacy of recording. Where a marine landscape, habitat or species has been assessed for national status, the following terms are used:
Globally important. A high proportion of the global extent of a marine landscape or habitat or a high proportion of the global population of a species (at some stage in its life cycle) occurs within the UK. 'High proportion' is considered to be 20% when known.
Regionally important. A high proportion of the regional (north-east Atlantic or European) extent of a marine landscape or habitat or a high proportion of the global population of a species (at some stage in its life cycle) occurs within the UK. 'High proportion' is considered to be 30% when known.
Criteria are also available for 'Decline' and 'Threat of significant decline' (Lieberknecht et al., 2003).
Further definitions are given for 'Rarity'. Marine landscapes, habitats and species that are sessile or of restricted mobility (at any time in their life cycle) are considered rare if their distribution is restricted to a limited number of locations.
Nationally rare. Scales to assess the rarity of species were developed by Sanderson (1996). The definition for 'Rare' is now (Lieberknecht et al., 2003) used for features (marine landscapes, habitats, populations of a species). Rarity is defined for marine benthic species by their occurrence in the 1,546 10km x 10km squares containing sea within the 3-mile limit of the territorial waters of Great Britain (England, Scotland and Wales) and the Isle of Man. The full range of definitions applied to species is given below. |
