The number of species in a given habitat, biotope, community or assemblage. The following scale is used to judge the likely response of species richness to an external factor.
|Major decline||The number of species in the community is likely to decrease significantly (>75% of species) in response to the factor, probably because of mortality and loss of habitat. For example, a change from very rich to very poor on the NHAP scale (Hiscock 1996).|
|Decline||The community is likely to loose some of its species in response to the factor by either direct mortality or emigration.|
|Minor decline||The community is likely to loose few species (<25% of species) in response to the factor. For example, a decrease of one level on the NHAP scale (Hiscock 1996).|
|No change||The factor is unlikely to change the species richness of the community|
|Rise||The number of species in the community may increase in response to the factor. (Note the invasion of the community by aggressive or non-native species may degrade the community).|
|Not relevant||It is extremely unlikely for a factor to occur (e.g. emergence of a deep water community) or the community is protected from the factor.|
Hiscock, K., 1996. Interpretation of data. In Marine Nature Conservation Review: Rationale and methods, ed. K. Hiscock, p.73-84. Peterborough, Joint Nature Conservation Committee.