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Biodiversity & Conservation

Typical Abundance in Britain

High Density Species that are found in high numbers in their appropriate habitats. Equivalent to Superabundant and Abundant on the MNCR SACFOR abundance scale (see below).
Moderate Density Species that are found in moderate numbers in their appropriate habitats. Equivalent to Common and Frequent on the MNCR SACFOR abundance scale (see below).
Low Density Species that are found in low numbers in their appropriate habitats. Equivalent to Occasional and Rare on the MNCR SACFOR abundance scale (see below).
Very Low Density Species that are found in very low numbers in their appropriate habitats. Equivalent to less than Rare on the MNCR SACFOR abundance scale (see below).

Marine Nature Conservation Review (MNCR) Abundance Scales

Abundance scales used for both littoral and sublittoral taxa from 1990 onwards

S = Superabundant, A = Abundant, C = Common, F = Frequent, O = Occasional, R = Rare, L = Less than rare indicated by extrapolation.

Growth form Size of Individuals / Colonies
% Cover Crust /Meadow Massive /Turf <1 cm 1-3 cm 3-15 cm >15 cm Density
> 80% S S > 1 /0.001 m2 (1x1 cm) >10,000 / m2
40-79% A S A S 1-9 /0.001 m2 1,000-9,999 / m2
20-39% C A C A S 1-9 /0.01 m2 (10 x 10 cm) 100-999 / m2
10-19% F C F C A S 1-9 /0.1 m2 10-99 / m2
5-9% O F O F C A 1-9 / m2
1-5% or density R O R O F C 1-9 / 10 m2 (3.16 x 3.16 m)
< 1% or density L R L R O F 1-9 /100 m2 (10 x 10 m)
L L R O 1-9 /1000 m2 (31.6 x 31.6 m)
L R <1 /1,000 m2 (100x100 m)
L <1 /10,000 m2 (1km2)