Natural environment and biodiversity

Biodiversity impact assessment calculator

Local Plan Policy NEB1: General Strategy for Biodiversity, requires that “development proposals should result in net gains to biodiversity wherever possible.”

The Defra biodiversity impact assessment metric is considered to be the appropriate method for determining ecological value and delivering net measurable ecological gain. The Defra metric and supporting guidance documents can be downloaded from the Natural England website.

In order to use the tool, applicants will require the following: 

  • habitat type
  • habitat condition
  • area or length of each habitat, hedgerow or linear feature
  • the impact from development, both direct (onsite) and indirect (offsite)
  • onsite biodiversity mitigation/enhancement measures

The survey and calculation should include the whole of the development boundary (red line) as a minimum. The survey should include habitats within the entire ownership boundary (blue line), as ecological compensation can be incorporated within this boundary. All habitat compensation measures within the ownership boundary should be included within the calculation as both existing and proposed habitats.

A development master plan or indicative plan is necessary to inform the assessment as this will determine the habitats that will be in place post-development, including habitats to be retained and enhanced. It is therefore essential that the ecologist and landscape architect work together.