BCT has been working on defining Core Sustenance Zones (CSZs) for different bat species through an extensive literature review (attached below with references).

A CSZ refers to the area surrounding a communal bat roost within which habitat availability and quality will have a significant influence on the resilience and conservation status of the colony using the roost.

With reference to development, the CSZ could be used to indicate:

The area surrounding a communal roost within which development work may impact the commuting and foraging habitat of bats using that roost.

The area within which it may be necessary to ensure no net reduction in the quality and availability of foraging habitat for the colony.