Biodiversity net gain is an approach to planning and land management that leaves the natural environment in a better state than it was before. Developers will be required to demonstrate that proposals deliver biodiversity net gain.
New planning requirements called Mandatory Biodiversity Net Gain came into force in 2024. These new rules are applied to major development applications from February 2024 and to most other development from April 2024.
You will need to understand the requirements of biodiversity net gain if you are a:
- developer
- land manager
- local planning authority
How biodiversity net gain is measured
The government has produced the biodiversity metric 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. Achieving 10% net gain means fully compensating for losses of habitat on a development site, but then going further so that overall, there is a gain in Biodiversity Units of at least 10% as a result of the development process.
See guidance about using the biodiversity metric on the government website.
How biodiversity net gain will affect your development
Under the Environment Act 2021, planning permissions granted in England, with a few exemptions, have to deliver at least 10% biodiversity net gain, using the biodiversity metric to demonstrate this. This applies to major development from 12 February 2024 and minor development from 2 April 2024.
Learn about exempt developments on the government website.
How minor developments are defined
For residential, minor developments are those:
- 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
- where the number of dwellings to be provided is not known, a site area of less than 0.5 hectares
For non-residential, minor developments are those:
- where the floor space to be created is less than 1,000 square metres
- where the site area is less than one hectare
Types of developments exempt from biodiversity net gain requirements
- development impacting habitat of an area below a ‘de minimis’ threshold of 25 square metres - for example, 5 metres by 5 metres
- householder applications
- biodiversity gain sites - where habitats are being enhanced for wildlife
- small scale self-build and custom housebuilding
How the process works
The Environment Act 2021 makes all planning permissions subject to a pre-commencement condition requiring the submission of a plan that demonstrates how 10% net gain will be achieved. The management of the habitat created to achieve this must then be secured by legal agreement for a minimum period of 30 years.
The habitat creation required to achieve 10% net gain should be undertaken on the development site itself. However, if space and circumstances do not allow this, provision on a separate site or a mixture of the two would be considered.
Offsite habitat creation can be undertaken on land owned by the developer, or on third party land where the landowner is willing to undertake such work and maintain it for at least 30 years in return for a payment from the developer.
The government introduced a national biodiversity credits purchase system for developments unable to meet their biodiversity net gain requirements locally. National biodiversity credits are a last resort and will be much more expensive than securing biodiversity units more locally. We will need evidence that all reasonable efforts have been made to buy the additional habitat creation locally.
Information to submit with a planning application
The biodiversity net gain process is built around the pre-commencement condition, which is when the full details of the metric calculations and of the measures to be taken to secure 10% net gain are required. However, enough information will need to be submitted with the planning application for the authority to be satisfied that a suitable net gain solution exists for that development.
The biodiversity information submitted with the planning application should include the metric calculations, and pre- and post-development habitat maps, showing details of the development of habitat creation to achieve net gain. This work should be undertaken by an experienced Ecologist and will allow the pre-commencement condition to be discharged without delay.
Minimum validation requirements
- correctly completed application form
- completed statutory biodiversity metric. Guidance on statutory biodiversity metric tools and guides can be found on the government website
- statement: Confirming if the biodiversity value of the on-site habitat is lower on the date of the application (or earlier date) because of degradation/result of ‘trashing’ in which case the value must be immediately before degradation and evidence to support this
- description of any on-site irreplaceable habitats: on land to which the application relates and exists on the date of application
- plan (at a recognised scale): with North identified showing on-site habitat on the date of application including irreplaceable habitat. This should be shown within the red outline, not blue, on the site location plan
Applicable to
- full applications for major development
- outline applications for major development
- S73 applications for major developments - only applicable in cases where the original planning application was received on or after the BNG implementation date
- full applications for minor development
- outline applications for minor development
Check the legislation
Information you need for biodiversity net gain (BNG) on GOV.UK
Biodiversity net gain in the Environment Act 2021
Guidance and advice
Guidance: Understanding biodiversity net gain on GOV.UK
Meet biodiversity net gain requirements: steps for developers
An introduction to Biodiversity Net Gain from the Future Homes Hub
How this affects existing legislation and policy
The biodiversity net gain process introduces a quantitative framework for securing and demonstrating net gain. It does not replace the requirement to carry out other assessments of impacts on biodiversity, for example, submission of bat survey information. Where there is the potential for impacts on European sites, such as Special Areas of Conservation or Special Protection Areas, the authority will still need to undertake a Habitats Regulations Assessment.
Compliance with several other environmental planning policies will still need to be demonstrated by the developer. This includes requirements relating to:
- protected or important nature conservation sites
- protected or important species
- irreplaceable habitats
Biodiversity net gain maintains the mitigation hierarchy of avoiding impacts first, then mitigating and only compensating as a last resort. It cannot be used to bypass the mitigation hierarchy.
Preparing for biodiversity net gain early in your development planning
The biodiversity metric has been designed to discourage the loss of better-quality habitats to development, by making them significantly more expensive to provide net gain for compared to lower value habitats.
Consequently, it is important to establish the baseline value of a site as early as possible when considering its development potential. The loss of higher value habitats may make a scheme non-viable or may require that parts of the site are safeguarded from development to enable an economically viable scheme to be developed.
Clearing sites in advance
Within Schedule 14 of the Environment Act measures have been included that allow the local planning authority to take account of any habitat degradation or destruction undertaken on a site since January 2020, and to take the earlier habitat state as the baseline for the purposes of biodiversity net gain. This is to ensure that there is no advantage to be gained by the deliberate clearance of land in order to achieve a low baseline value for biodiversity net gain.
If habitats on site have been destroyed or degraded prior to a survey and submission of planning application, the earlier habitat state will be taken as the baseline for the purposes of the biodiversity metric and a habitat condition score of ‘good’ will be allocated to the habitat parcel as a precaution.
Habitats of Strategic Significance in North Yorkshire mapping tool
The Biodiversity Net Gain metric includes a multiplier which can boost the score of habitats in particular locations. We have developed an interim strategic significance map which developers and their agents may consult to see if they can apply the multiplier.
This mapping represents our formally identified local strategy for determining areas of strategic significance until our Local Nature Recovery Strategy is published. In the Statutory Biodiversity Metric the strategic significance drop-down option ‘formally identified in local strategy’ can be applied to habitat parcels which fall within the relevant network. The four networks are:
- grassland
- woodland
- heathland
- wetland
View the Habitats of Strategic Significance in North Yorkshire mapping tool
Further information
Natural England biodiversity net gain brochure
Natural England biodiversity net gain metric and user guide
CIEEM biodiversity net gain report and audit templates
Definitions for biodiversity net gain - UKGBC
DEFRA land use policies and framework blog