Biodiversity net gain (BNG)

The information below sets out our response to some common issues and questions about our approach to biodiversity net gain (BNG) for developers and those with an interest in the subject.

Minimum level required BNG

The law mandates delivering a minimum biodiversity uplift of at least 10% in addition to standard biodiversity mitigation and compensation measures.

Mandatory BNG and development types

BNG is mandatory for all major applications submitted on and after 12 February 2024 and small site applications submitted on and after 2 April 2024, as per development definitions within Town and Country Planning Act (1990) (legislation.gov.uk).

Small sites are defined by the following:

1. Residential development: where the number of dwellings to be provided is between one and nine (inclusive), or if this unknown, a site area of less than 0.5 hectares.
2. Other development: where the floor space to be created is less than 1,000 square metres or where the total site area is less than one hectare, and is not the winning and working of minerals or the use of land for mineral-working deposits, or waste development.

There are however developments that are exempt from the BNG requirement.

Exemptions to mandatory BNG

Exemptions include:

• Development impacting habitat of an area below a ‘de minimis’ threshold of 25 square metres, or 5m for linear habitats such as hedgerows and watercourses (excluding priority habitat, listed under Section 41 of the Natural Environment and Rural Communities Act 2006)
• Householder applications
• Biodiversity gain sites
• Small scale self-build and custom housebuilding

However, developments exempt from mandatory net gain still require opportunities for biodiversity enhancements in accordance with local and national policies.

Mandatory national BNG does not apply to permitted development and prior approval applications.

Find further details on exemptions on the Gov.UK website.

How is BNG measured?

BNG is measured using the Statutory Biodiversity Metric, a tool that guides designs and land management decisions to support biodiversity better. The metric divides the baseline assessment into three different unit modules based on habitat type. These can be ‘area’, ‘hedgerow’ or ‘watercourse’ unit modules, each subject to its 10% net gain requirement. The catalogued habitats are converted into biodiversity units, which are used as proxy for habitat value. Habitat value is determined based on distinctiveness, extent, condition, and strategic significance.

For more information on how BNG is measured, please visit the User Guide (GovUK).

How do we consider strategic significance?

Strategic significance is the local significance of a habitat based on its location and habitat type. Assessors should assign a strategic significance category within the Metric for each individual habitat parcel both at baseline and at post-intervention. In the absence of the Local Nature Recovery Strategy (LNRS), assessors should use published plans, strategies or polices which are relevant to the habitat’s location to determine the strategic significance of the habitat and reference the relevant documents in their justification.

Further local guidance on strategic significance will be updated within our guidance as soon as possible.

What biodiversity metric should be used?

For all applications not classed as exempt or small, the statutory full biodiversity metric must be used, completed by a competent ecologist. All sites containing a watercourse (excluding culverts and ditches) will require a River Condition Assessment undertaken by an accredited River MoRPh surveyor.

Small sites have a separate metric, which must be completed by a competent person (someone with relevant qualifications, training, or experience in ecological fields).

In cases where priority habitats, irreplaceable habitats (GovUK), protected sites, and/or European protected species are present on site, or the habitats on site are not listed within the small site metric, then the full metric must be used. For any off-site interventions as part of small site developments, a full metric will need to be used, and land managers will need to complete the off-site tab.

For more information, please visit the DEFRA guidance on statutory biodiversity metric tools.

Where should BNG be delivered?

BNG should ideally be achieved on-site, following the biodiversity gain hierarchy. Off-site BNG should be located as close as possible to the development site to benefit local biodiversity and communities. Further details on the biodiversity gain hierarchy can be found in the GovUK website.

Significant on-site and all off-site BNG land will need to be formally registered on the Natural England Biodiversity Gain Site Register. At present, applicants will need to arrange BNG offsets within their own landholdings or with a third-party, such as landowners and habitat banks. Currently, we  are unable to provide a list of third-party participants or act as a broker. As a last resort, applicants can purchase credits from the statutory biodiversity credit scheme (GovUK), which go towards habitat creation plans across the UK. However, this will need to be approved by us prior to purchase, and applicants will need to justify how they have rigorously followed the BNG principles and rules.

Supporting information and planning applications

The following information must be submitted for applicable applications:

Where an applicant believes the development would be subject to the biodiversity gain condition, the application must be accompanied by minimum information set out in Article 7 of The Town and Country Planning (Development Management Procedure) (England) Order 2015 (legislation.gov.uk):

• confirmation that the applicant believes that planning permission, if granted, the development would be subject to the biodiversity gain condition;
• the pre-development biodiversity value(s), either on the date of application or earlier proposed date (as appropriate) (GovUK);
• where the applicant proposes to use an earlier date, this proposed earlier date and the reasons for proposing that date;
• the completed metric calculation tool (GovUK) showing the calculations of the pre-development biodiversity value of the onsite habitat on the date of application (or proposed earlier date) including the publication date of the biodiversity metric used to calculate that value. The metric should be submitted in its entirety, as an Excel spreadsheet (macros disabled). Do not delete unpopulated tabs, even if they are not relevant to the application;
• a statement 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’ GovUK website), 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;
• a description of any irreplaceable habitat (GovUK) (as set out in column 1 of the Schedule to the Biodiversity Gain Requirements (Irreplaceable Habitat) Regulations 2024) (legislation.gov.uk) on the land to which the application relates, that exists on the date of application, (or an earlier date); and
• plan(s), drawn to an identified scale and showing the direction of North, showing onsite habitat existing on the date of application (or earlier proposed date), including any irreplaceable habitat (if applicable).

If this information has not been provided, the Council will likely refuse to validate the application. Within the planning application form applicants will be asked to confirm whether this information accompanies the application. Where these details have been provided elsewhere in accompanying documents, applicants are encouraged to cross-reference to these rather than duplicate this information within the application form.

A draft Biodiversity Gain Plan (GovUK) is encouraged to be submitted at the validation stage to provide information on the strategy on how BNG is to be delivered and secured.

How do I demonstrate exemption?

Where an applicant believes the proposal is exempt from providing BNG, this must still be accompanied by a statement explaining why it is believed to be exempt. The evidence required to demonstrate exemption will depend upon the basis of the exemption. Examples of scenarios of exemptions are provided in the national BNG Planning Practice Guidance (GovUK).

BNG pre-commencement condition

If the LPA is satisfied that at least 10% biodiversity net gain is capable of being achieved, the general biodiversity gain condition will be attached to the planning permission. This will require the submission, and subsequent implementation, of a full Biodiversity Gain Plan.

Required pre-development BNG information

A finalised Biodiversity Gain Plan (GovUK), using Defra’s template or equivalent set of information, must be submitted and approved by the LPA, prior to the commencement of development. This must then be implemented in accordance with the General Biodiversity Condition.

Details on Biodiversity Gain Plan covers the following aspects:

• Submission details e.g. data, planning application number, name of LPA
• How the biodiversity gain hierarchy has been followed
• Arrangements for maintenance and monitoring of habitats
• Completed biodiversity metric calculation tool (as an Appendix)
• Pre-development and post-development biodiversity values
• Irreplaceable habitats information including bespoke compensation, if relevant
• Registered off-site gains allocated to the development
• Value of the registered off-site gain in relation to the development
• Purchase biodiversity credits, if relevant
• Pre- and post-development plans

A Habitat Management and Monitoring Plan (GovUK) using Defra’s template or equivalent set of information, must be submitted and approved, prior to commencement of development, if the site includes significant on-site habitat enhancements. The definition of significant on-site habitat enhancements will be considered on a case by case basis in line with the latest guidance.

How is BNG secured?

Significant on-site and off-site BNG must be legally secured for a minimum of 30 years, typically through planning conditions, S106 agreements and conservation covenants.

For more information, please visit the DEFRA guidance on legal agreements to secure BNG (GovUK).

How is BNG progress monitored?

Applicants are responsible for monitoring BNG progress and submitting reports (naturalengland.org.uk) to us at agreed intervals across the management and monitoring period. Reports should contain relevant data, including biodiversity targets, habitat condition assessments, updated statutory metric, details of progress towards target conditions, changes since last monitoring report, recommendations for changes to the Biodiversity Gain Plan as appropriate, and updated GIS shapefiles where necessary.

Further information

• Biodiversity Net Gain pages on GovUK.
• Natural England’s brochure on net gain
• CIEEM: Biodiversity Net Gain Report and Audit Templates (includes useful templates for Biodiversity Gain & monitoring reporting)
• Planning Advisory Service (PAS) Biodiversity Net Gain FAQs
• DEFRA Biodiversity Metric Download User Guide and Metric
• The Small Sites Metric
• BSI Standards Publication: Biodiversity – Code of practice for planning and development