Biodiversity Net Gain (BNG)

These are the new 2024 requirements for biodiversity net gain for most housing, industrial and commercial developments.

What is Biodiversity Net Gain (BNG)?

Biodiversity net gain is a way of creating and improving biodiversity by requiring development to have a positive impact (‘net gain’) on biodiversity. Where a development has an impact on biodiversity, Biodiversity Net Gain encourages developers to provide an increase in appropriate natural habitat and ecological features over and above that being affected in such a way it is hoped that the current loss of biodiversity through development will be halted and ecological networks can be restored.

Key components

In England, biodiversity net gain is required under a statutory framework introduced by Schedule 7A of the Town and Country Planning Act 1990 (inserted by the Environment Act 2021).

The Environment Act (Opens in a New Window) sets out the following key components of mandatory biodiversity gain:

  • Amends the Town & Country Planning Act (TCPA);
  • Minimum 10% gain required calculated using the Biodiversity Metric and approval of a biodiversity gain plan;
  • Significant on-site habitat and all off-site habitat secured for at least 30 years via conditions, planning obligations or conservation covenants;
  • Delivered on-site, off-site or via a new statutory biodiversity credits scheme; and
  • National register for net gain delivery sites.

It does not change existing legal protections for important habitats and wildlife species. It maintains the mitigation hierarchy of avoid impacts first, then mitigate and only compensate as a last resort.

When will BNG become mandatory?

The mandatory requirement came into place on 12 February 2024 for all Town and Country Planning Act development with some exemptions and at this stage only for major development. BNG will be required for development defined as minor development (again with some exemptions) from 2 April 2024. 

For reference, small sites minor developments are defined as:

  • For residential; where the number of dwellings to be provided is between one and nine inclusive on a site having an area of less than one hectare, or where the number of dwellings to be provided is not known, a site area of less than 0.5 hectares.  
  • For non-residential: where the floorspace to be created is less than 1,000 square metres or where the site area is less than one hectare.

You can find the full list and explanation of exemptions to mandatory BNG on their website (Opens in a New Window).

What is Biodiversity Metric?

The Biodiversity Metric (Opens in a New Window) is a habitat-based approach to determining a proxy biodiversity value on site, which developers must use to calculate a minimum 10% gain on the pre-development biodiversity value of the site. The metric calculates Biodiversity Units based on the habitats present on site or proposed to be created. Mandatory BNG will require use of the latest version of the Biodiversity Metric.

What is on-site and off-site for BNG?

  • ‘On-site’ includes all land within the boundary of a project. In a planning context, this usually means within a red line boundary.
  • ‘Off-site’ is all land outside of the on-site boundary, regardless of ownership.

What is a Biodiversity Gain Plan?

This is a document which sets out how a development will deliver biodiversity net gain and allows the planning authority to check whether the proposals meet the biodiversity gain objective.

The Environment Act sets out that development subject to mandatory BNG will be required to submit a Biodiversity Gain Plan for planning authority approval once planning permission is granted, which will be secured by way of a pre-commencement condition. The Act sets out that the plan should cover:

  • How adverse impacts on habitats have been minimised;
  • The pre-development biodiversity value of the onsite habitat;
  • The post-development biodiversity value of the onsite habitat;
  • The biodiversity value of any offsite habitat provided in relation to the development;
  • Any statutory biodiversity credits purchased; plus
  • Any further requirements as set out by Government policy (Opens in a New Window).

What is the national biodiversity credits scheme?

This is a scheme set out by the Secretary of State for a system of statutory biodiversity credits that will be invested in habitat creation. The biodiversity credits scheme allows the UK government to sell biodiversity credits to developers if the required biodiversity net gains cannot be achieved on-site or through the off-site market. The prices of biodiversity credits LINK are set higher than prices for equivalent biodiversity gain on the market. Natural England will sell statutory biodiversity credits on behalf of the Secretary of State.

Further information

There is a large amount of information available online from the Government (specifically DLUHC and Defra).

Some useful links are provided below:

The Planning Advisory Service has published guidance for Local Planning Authorities (LPAs) which may also be of interest:

For more information in relation to BNG and planning applications please contact:

Planning Administration
tel: 0115 917 7777