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Biodiversity Net Gain (BNG)

What is BNG?

Biodiversity Net Gain (BNG) is an approach to development, land and marine management that leaves biodiversity in a measurably better state than before the development took place (Natural England).

BNG is additional to existing habitats and species protections. Intended to reinforce the mitigation hierarchy, BNG aims to create new habitats as well as enhancing existing habitats, ensuring the ecological connectivity they provide for wildlife is retained and improved (Natural England).

What planning applications does it apply to?

BNG became a mandatory requirement of the Environment Act 2021 for major developments (unless exempt) from 12th February 2024, for small sites from 2nd April 2024 and it will be required for Nationally Significant Infrastructure Projects (NSIPs) from November 2025.

Major development sites are defined as the following:

  • For residential: where the number of dwellings to be provided is 10 or more units or the site area is larger than 0.5 hectares.
  • For non-residential: where the floor space to be created is 1,000 square metres or greater or where the site is one hectare or larger.

Small sites are defined as:

  • For residential: where the number of dwellings is between one and nine, or if this is unknown, the site area is less than 0.5 hectares.
  • For non-residential: where the floor space to be created is less than 1,000 square metres or the total site area is less than one hectare.

Exemptions include the following:

  •  Permitted development
  • Householder applications
  • Development impacting habitat of an area below a threshold of 25m2, or 5m for linear habitats (De Minimis)
  • Biodiversity gain sites
  • Small scale self-build and custom housebuilding

How is BNG measured?

The Statutory Biodiversity Metric tool published by Natural England uses 'biodiversity units' to measure the value of a habitat.

Units are calculated based on the size, distinctiveness, condition and strategic significance of the habitat.

  • On-site units: habitat enhancement/creation via landscaping/green infrastructure within the red line of the application site.
  • Off-site units: habitat enhancement/creation via habitat banks with public and private landowners, on land outside of the red line of the application site.
  • Statutory credits units: for use only when it is not possible to deliver on-site and/or off-site.

What will I need to submit with my planning application?

The following is required to validate a planning application in relation to BNG:

  • Planning Application Form (ensuring biodiversity section is completed)
  • Statutory Biodiversity Metric - pre completion (post completion required for on-site BNG)
  • Existing Biodiversity Site Plan
  • Draft BNG Plan for on-site delivery
  • Draft Habitat Management and Monitoring Plan (HMMP) required for on-site delivery.

Further detail on validation requirements can be found on the Council's validation list in due course, as well as the BNG Guidance Note for Applicants:  Biodiversity Net Gain Advice Note for Applicants April 2024 (PDF) [2MB]

What will I need to provide after I get planning permission?

The statutory framework for biodiversity net gain requires a Biodiversity Gain Plan to be submitted and approved to discharge the general biodiversity gain condition prior to the commencement of development. There is a Biodiversity Net Gain Plan template to be completed and submitted.

A Habitat Management and Monitoring Plan (HMMP) is also required to demonstrate how the biodiversity enhancements will be managed and monitored for a minimum period of 30 years. There is a Habitat Management and Monitoring Plan (HMMP) template to be completed and submitted.

The finalised Biodiversity Gain Plan and HMMP must be submitted through the Discharge of Conditions application process.

How will BNG be secured?

Significant on-site habitat and all off-site habitat will need to be secured for at least 30 years via conditions, planning obligations or conservation covenants. Other potential conditions could include monitoring and reporting arrangements.

Further information

Further information is available on GOV.UK

Planning Advisory Service BNG Frequently Asked Questions available on Biodiversity Net Gain FAQs - Frequently Asked Questions | Local Government Association