A measure of how strongly species are associated with calcareous (chalk and limestone) grassland habitats.
- High: species routinely recorded from calcareous grasslands. They may also be recorded to a greater or lesser degree from other open habitats on freely draining soils, but it is likely that they are mainly dependent on calcareous grasslands to sustain viable populations.
- Moderate: species routinely recorded from calcareous grasslands, but also from semi-natural open habitats on freely-draining soils over all or part of their geographical area of distribution.
- Low: species frequently recorded in numbers from calcareous grasslands, but predominantly associated with other types of open habitats over all their British area of distribution.
For more information see: Alexander, K.N.A. (2003) A review of the invertebrates associated with lowland calcareous grassland. English Nature Research Report 512.