Biodiversity Net Gain (BNG)

What is BNG?

BNG is an approach to development. It makes sure that habitats for wildlife are left in a measurably better state than they were before the development.

BNG requires developers to deliver a minimum 10% biodiversity net gain to ensure the development improves existing habitats or creates new habitats. This is in addition to existing legislation for protected habitats and species.

There are 3 ways a developer can achieve BNG.

They can create biodiversity on-site (habitat enhancement/creation via landscaping/green infrastructure within the red line boundary of a development site).
If developers cannot achieve all of their BNG on-site, they can deliver through a mixture of on-site and off-site. Developers can either make off-site biodiversity gains on their own land outside the development site or buy off-site biodiversity units on the market.
If developers cannot achieve on-site or off-site BNG, they must buy statutory biodiversity credits from the government. This should be a last resort. The government will use the revenue to invest in habitat creation in England. Further information about statutory credits can be found here.

BNG became a mandatory requirement of the Environment Act 2021 for major developments (unless exempt) from the 12th of February 2024, for small sites from the 2nd of April 2024 and it will be required for Nationally Significant Infrastructure Projects (NSIPs) from May 2026.

Major development sites are defined as follows:

For residential: 10 or more dwellings; 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 more; or where the site is 1 hectare or more.

Small sites are defined as follows:

Residential: 1-9 dwellings on a site of an area 1 hectare or less; or, site area is less than 0.5 hectares.
Non-residential: floor space created is less than 1,000 square metres or the total site area is less than 1 hectare.

What you will need to submit with your planning application

All developers should submit a:

Completed statutory biodiversity metric and condition assessment* (as an Excel-file type). For minor developments only, a completed small sites biodiversity metric (as an Excel-file type);
Scaled site plan, showing on-site habitat existing on the date of application (or an earlier date), including any irreplaceable habitat as set out in the Schedule to the Biodiversity Gain Requirements (Irreplaceable Habitat) Regulations 2024 on the land to which the application relates that exists on the date of the application (or an earlier date);
Date of assessment;
Statement as to whether activities have been carried out prior to the date of application (or earlier proposed date), that result in loss of onsite biodiversity value (‘degradation’)**, and where they have:
a statement to the effect that these activities have been carried out;
the date immediately before these activities were carried out;
the pre-development biodiversity value of the onsite habitat on this date;
the completed metric calculation tool showing the calculations, and
any available supporting evidence of this.

*The calculation tools and guides for measuring the biodiversity value of habitat for biodiversity net gain (BNG) can be found here.
**Paragraph 6 of Schedule 7A of the Town and Country Planning Act 1990 highlights the following in regard to habitat degradation:

Where unauthorised degradation of the onsite habitat has taken place on the land between the 30th of January 2020 and the relevant date of the application, not related to the planning permission
If activities to implement or in connection with a planning permission are carried out after the 25th of August 2023 that lower the biodiversity value of the onsite habitat

Where an exemption is claimed, further justification may be required. For further information on exemptions, please click here.

What you will need to submit before commencement of works

Further to an approved application, a final Biodiversity Gain Plan with a Habitat Management and Monitoring Plan (HMMP) will need to be submitted and approved by the Council before work can start.
A Biodiversity Gain Plan submission should include the following (where relevant):

The completed metric tool calculation showing the calculations pf the pre-development and post-intervention biodiversity values
Pre-development and post-development plans (showing the location of on-site habitat, the direction of north and drawn to an identified scale)
Compensation plan if the development effects irreplaceable habitats
BNG register reference numbers if using off-site units
Proof of purchase if buying statutory biodiversity credits
A description of how significant on-site gains will be managed and monitored (with a Habitat Management and Monitoring Plan)
A commitment to deliver and maintain BNG for a minimum of 30 years from the date of completion of the development (for on-site) or from the date that BNG has been completed (off-site)

For phased developments there are separate requirements. Developers will need to submit a statement showing how the development will proceed in phases alongside an Overall Biodiversity Gain Plan before any development can commence. No development can then commence within each specified phase until a Phase Biodiversity Gain Plan for that phase has been submitted and approved.

Templates for these documents can be found below:

Draft Supplementary Planning Document

The Council consulted on a draft Supplementary Planning Document in early 2024. This has not been adopted by the Council; however, it is a useful resource that provides guidance on the implementation of BNG and how it will impact your planning application. The documents consulted on can be found below:

Biodiversity Net Gain (BNG) Supplementary Planning Document January 2024 [pdf] 799KB

Strategic Environmental Assessment and Habitats Regulations Assessment Screening Report [pdf] 427KB

Further information and support

You can find more details about BNG on Understanding Biodiversity Net Gain and Biodiversity net gain - GOV.UK