Biodiversity & Conservation

MarLIN Glossary

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N

National Importance
1) biotopes and areas (conservation assessment) - Biotopes or areas which are highly rated in the coastal sector will be described as of national importance if they are one of the best examples or only examples known in Great Britain. This was, until 1995, defined for communities as being, "outstandingly good examples of their type in Britain". National importance can apply to biotopes which are, or are likely to be, widely occurring in other similar physiographic situations in the north-eastern Atlantic. (Based on Hiscock & Mitchell, 1989). Cf. 'national importance: species', 'international importance', 'local importance', 'regional importance' (biotopes or areas and species). 2) species (conservation assessment) - considered to be those benthic species which are nationally rare or nationally scarce (q.v.). Until 1995, defined as: "Species which are recorded at only a few locations in Britain but are more widespread in other parts of the north-east Atlantic. Species recorded in higher numbers at locations under consideration than elsewhere in Britain or where the site is one of a very few locations where large quantities are recorded in Britain" (based on Hiscock & Mitchell, 1989). A species may also be nationally important where a high proportion of the world population occurs in Britain, even though the species might be widespread in Britain. A nationally important species could be one whose numbers are declining rapidly. Cf. 'national importance: biotopes and areas', 'international importance', 'local importance', 'regional importance' (biotopes or areas and species).

Nationally Rare
For marine conservation purposes, these are regarded as species of limited national occurrence (q.v. rarity). By analogy with the approach adopted in British Red Data Books (for instance, Bratton, 1991) but referring to sea areas within the three-mile limit of territorial seas, they are defined as those species known to occur in 0.5% or less (eight or fewer) of the 10 x 10 km squares containing sea within the three-mile limit of territorial seas for Great Britain (Sanderson, 1996). Cf. 'nationally scarce'.

Nationally Scarce
For marine conservation purposes, these are regarded as species of limited national occurrence (q.v. rarity). By analogy with the approach adopted in British Red Data Books (for instance, Bratton, 1991) but referring to sea areas within the three-mile limit of territorial seas, they are defined as those species known to occur in 0.5 to 3.5% (nine to 55) of the 10 x 10 km squares containing sea within the three-mile limit of territorial seas for Great Britain (Sanderson, 1996). Cf. 'nationally rare'.

Natural Habitat
As defined by the Habitats Directive (q.v.) "natural habitats means terrestrial or aquatic areas distinguished by geographic, abiotic and biotic features, whether entirely natural or semi-natural." (Commission of the European Communities, 1992).

Natural Range
The geographical range of a species in recent times (since about 5,000 BP) but excluding any changes to that range as a result of human agency.

Naturalness
In conservation assessment - the extent to which a location and its associated biotopes is unaffected by anthropogenic activities .

Nature Conservation
The regulation of human use of the global ecosystem to sustain its diversity of content indefinitely (Nature Conservancy Council, 1984).

Nautical Mile
A unit of distance used in navigation, equivalent to 1° of latitude. The standard, or international, nautical mile is 1852 metres; the true nautical mile changes length with latitude, from 1861.7 metres at the equator to 1842.9 metres at the poles.

Neap Tide
The astronomical tide of minimum range, occurring at the time of the first and third quarters of the moon.

Nekton
Actively swimming pelagic organisms able to move independently of water currents; typically within the size range 20 mm to 20 m (from Lincoln & Boxshall, 1987).

Neritic
Referring to coastal waters overlying the continental shelf (0 m to 200 m below chart datum) (based on Baretta-Bekker et al., 1992).

Neuston
1) Organisms similar to plankton, that inhabit the surface film of open water. 2) the ecosystem of the surface film of open water.

Niche
The ecological resource occupied by a species in a community or ecosystem.

Non-native (species)
A species which has been introduced directly or indirectly by human agency (deliberate or otherwise), to an area where it has not occurred in recent times (about 5,000 years BP) and which is separate from and lies outside the area where natural range extension could be expected (i.e. outside its natural geographical range (q.v.)). The species has become established in the wild and has self-maintaining populations; the term also includes hybrid taxa derived from such introductions ('derivatives'). (Cf. 'alien species'; 'introduced species'; 'recent colonist'; 'reintroduction'; 'translocation').

North Sea
1) As defined for the purposes of the North Sea Conferences it is southwards of 62ºN, eastwards of 5°W and northwards of 48º 30'N and includes the Kattegat defined by lines between coastal features (Oslo and Paris Commissions 1994 where it is described as the "Greater North Sea"). For the British coast, these are the seas to the east of Cape Wrath, and of Falmouth. This is the definition used by the JNCC for the Directory of the North Sea coastal margin (Doody, Johnston & Smith 1993) and elsewhere. 2) As defined by ICES: ICES subarea IV, being the sea east of 4° W to the north of Scotland, north of 51° N at the Straits of Dover, and south of 61° N.

North-eastern Atlantic
North Cape to the Straits of Gibraltar, excluding the Baltic.

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Glossary references