Biodiversity Net Gain

What is Biodiversity net Gain?

Biodiversity Net Gain (BNG) is an approach to development and land management which aims to leave biodiversity in a measurably better state than before. Under the Environment Act 2021, it will be mandatory for all planning permissions in England to achieve at least 10% net gain from 12 February 2024 for major development, and from 2 April 2024 for small sites, with some exemptions.

BNG provision should make a meaningful contribution to nature recovery in line with the Exmoor Nature Recovery Vision  and it must therefore be additional, over-and-above other mitigation or compensation requirements such as that required for protected species or priority habitats, not just what is lost as a result of an individual development. Development likely to result in the loss or deterioration of irreplaceable habitats or protected sites will not be permitted.

Exmoor National Park Technical Guidance Note

An Exmoor specific technical guidance note (TGN) has been produced to support implementation of the new BNG requirements and the delivery of the biodiversity enhancement Local Plan policy.  It requires applicants to provide a minimum of 10% net gain in biodiversity for a minimum of 30 years, as set out in the Environment Act 2021. The guidance also provides information on what is required to support a planning application, and ideas on how to make a meaningful contribution to nature recovery.

What other information is available to help with BNG?

The Natural Environment Record (NER) is Exmoor’s repository for biological information, containing wildlife data collected from throughout the National Park. It includes an interactive map which can help with finding information on Exmoor’s wildlife habitats, species and designations Exmoor - Natural Environment Record. For detailed data searches please contact the local records centre (Somerset Environmental Records Centre or Devon Biodiversity Records Centre).

This flow chart has been produced by Somerset Council (and edited by Exmoor National Park Authority) to help with BNG preparation and implementation by providing an overview of the process.

Small sites

BNG for small sites will not become mandatory until 2 April 2024 and therefore the small sites trial will continue for longer. Small sites are defined as residential developments of 1 - 9 dwellings on a site of less than one hectare, or any site less than 0.5 hectares. For non-residential development, small sites are defined as a floor space of less than 1,000m2, or a site of less than 1 hectare.

Exemptions and enhancement

Exemptions for BNG will apply for householder applications, permitted development, development impacting an area below a ‘de minimis’ threshold of 25m2 or 5m for linear habitats (where no priority habitat is present), biodiversity gain sites (where habitats are being enhanced for the purpose of fulfilling the biodiversity gain condition for another development), self-build and custom build (as defined in section 1(A1) of the Self-build and Custom Housebuilding Act 2015) where there will be no more than nine dwellings on a site no larger than 0.5ha and urgent crown development. BNG will also not apply to retrospective applications.

Development which is exempt from 10% BNG requirements can make a difference for wildlife and the National Park Authority will still require biodiversity enhancements to be incorporated into development proposals in line with the NPPF and Local Plan.

The Exmoor National Park Local Plan has policy hooks in it – Policy CE-S3 Biodiversity and Green Infrastructure and CE-D2 Green Infrastructure Provision. Part 4 Conserving and Enhancing Exmoor ( There is also a Local Plan Summary Local Plan 2011-2031 Summary ( .

Enhancements should be in line with these existing Exmoor National Park Local Plan policies. Requirements and thresholds are set out in Appendix 1 of the technical guidance note .

Where can I get further information or advice?

A range of resources has been produced nationally to help with understanding BNG and the new requirements including a number of videos Biodiversity Net Gain for local authorities | Local Government Association

Pre-application discussions are an important way to ensure that the development that comes forward is high quality and complies with local plan policies.

For further information or advice please do not hesitate to contact us on 01398 323665 or via