What is Biodiversity Net Gain?

Biodiversity Net Gain (BNG) is an approach to development that aims to leave the natural environment in a measurably better state than it was beforehand. BNG is a legal requirement introduced with The Environment Act 2021 and implemented by Schedule 7a of the Town and Country Planning Act 1990. BNG is in addition to any other biodiversity measures that may be required e.g. requirements to provide compensatory habitat for protected sites, habitats or species. Further information on BNG can be found on the GOV.UK website.

BNG is being introduced in two phases. From 12 February 2024 all ‘larger developments’ will be eligible and from 2 April 2024 ‘smaller’ developments will become eligible. Every eligible planning permission for the development of land in England shall be deemed to have been granted subject to the following general biodiversity gain condition:

Development may not be begun unless —

  1. a biodiversity gain plan has been submitted to the planning authority, and
  2. the planning authority has approved the plan.

This general planning condition cannot be removed, modified or disapplied.

BNG requires the submission of a Biodiversity Gain Plan post-permission. However, all eligible applications will need to submit information that meets the national minimum requirements.

Which developments are eligible?

A minimum of 10% BNG is mandatory for all new applications which meet the following criteria:

Larger developments


  • 10 or more dwellings + site area greater than 1 hectare; or
  • Unknown number of dwellings _ site area greater than 0.5 hectares


  • Floorspace is greater than 1000m2; or
  • Site area is greater than 1 hectare.

Smaller developments


  • Fewer than 10 dwellings + site less than 1 hectare
  • Number of dwellings not known + site less than 0.5 hectares


  • Floor space to be created is less than 1,000m2
  • Site area is less than 1 hectare

Individual householder applications are exempt from BNG requirements, as are certain other development types. Further information on exemptions can be found on the GOV.UK website.

Delivering BNG

BNG delivery will require specialist technical input, normally from a professional ecologist. BNG can only be calculated using the Statutory Biodiversity Metric. It is strongly recommended that specialist expertise is sought and that applicants engage in pre-application discussions with Havant Borough Council to ensure that mandatory BNG can be delivered.