Biodiversity net gain planning advice

What you need to know about biodiversity net gain to help you complete a planning application or are managing land.

Biodiversity net gain (BNG) is an approach to planning and land management that leaves the natural environment in a better state than it was before.

You must show that your proposals deliver biodiversity net gain.

You will need to understand the requirements of BNG if you are a:

  • developer
  • land manager

Contents:

How BNG is measured and calculated

Under the Environment Act 2021, planning permissions granted in England, with a few exemptions, will have to deliver at least 10% biodiversity net gain, using the biodiversity metric to demonstrate this.

The Biodiversity Metric is used to calculate the value of all habitats within the development site (usually the red line boundary) for two scenarios; before and after development.

The current version of the metric is the statutory metric. The values of the habitats are measured in ‘biodiversity units’.

GOV.UK provide statutory biodiversity metric tools and guides.

The pre-development number of biodiversity units is compared to the post-development number of biodiversity units to assess if net gain is achieved.

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.

Mandatory requirements and exemptions

BNG applies to both major and minor development with some exceptions.

Definition of a minor development

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

Exemptions

The biodiversity gain condition does not apply to the following types of development:

  • development impacting habitat of an area below a threshold of 25 square metres - for example, five metres by five metres
  • householder applications
  • biodiversity gain sites - where habitats are being enhanced for wildlife
  • small scale self-build and custom housebuilding

The BNG process

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. 

BNG can be delivered:

  • on site – by creating or enhancing habitats to generate additional biodiversity units within the red line boundary of the development site.
  • off site – by creating or enhancing habitats to generate additional biodiversity units outside the red line boundary of the development site.
  • via Statutory biodiversity credits – by paying to purchase biodiversity credits from the UK Government’s credit sales service. Two credits will be required for every one unit to be compensated for.
  • via a combination of the above

The national biodiversity credits purchase system outlines credit prices. It is designed 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.

Planning applications and BNG

There are national validation requirements set by the UK Government and outlined in the GOV.UK Biodiversity Net Gain Planning Practice Guidance. 

These requirements are set out in the application form that you need to submit to us when applying for planning permission.

The requirements are:

  • correctly completed application form
  • completed statutory biodiversity metric or small sites metric, GOV.UK guidance on statutory biodiversity metric tools and guides
  • 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

The metric will be subject to validation. If the following rules are not met the application may not be validated.

The metric must:

  • be supplied as an Excel spreadsheet - screenshots or PDF versions will not be acceptable
  • be supplied with all start page details filled out – ‘completed by’, ‘date of completion’
  • have ‘the Statutory Biodiversity Metric’ as the ‘Start’ tab title
  • be supplied with no input error/rules and principles not met flags (i.e. red boxes) after Row 10 on the ‘On-Site Habitat Baseline’ tab
  • report the same site area as the application form and supplied redline boundary

All condition assessment sheets used to complete the metric must be supplied with the metric tool.

Assigning strategic significance within the Biodiversity Metric

Strategic significance interim guidance

Strategic significance is defined by the Biodiversity Metric User Guide as “the local significance of the habitat based on its location and habitat type”. 

Planning applicants and BNG unit providers must assign strategic significance by completing the strategic significance drop-down for each habitat parcel within all three modules of the Statutory Biodiversity Metric.

Until Cumbria’s Local Nature Recovery Strategy is published, planning applicants and BNG unit providers must have regard to our Interim Strategic Significance Guidance (PDF , 611KB).

When assigning strategic significance within all three modules of the Statutory Biodiversity Metric the Interim Strategic Significance Guidance must be used in conjunction with the Cumbria Local Nature Recovery Network interactive map.

Strategic significance transition guidance

Once the Cumbria Local Nature Recovery Strategy (LNRS) is published, the interim guidance will be withdrawn and the published LNRS together with the appropriate biodiversity metric user guide must be used to assign strategic significance.

The anticipated publication date of the final the LNRS is 31 October 2025.

During the transition between consultation draft and final publication users should continue to refer to the interim strategic significance guidance.

Implications for submitted but undetermined planning applications once the LNRS is published

On and off-site baseline biodiversity values:

  • the publication of the Cumbria LNRS whilst an application is live will not require any changes to the strategic significance multiplier applied to baseline habitat values

On and off-site post-development biodiversity values

  • if the value of the post-development biodiversity units derived through the metric calculations is likely to be altered by changes to the strategic significance multiplier, the values must be reassessed following the guidance in the latest version of the Statutory Biodiversity Metric User Guide, together with the published Cumbria LNRS
  • where updates are required, any revised documents, including the metric calculation tool, draft Habitat Management and Monitoring Plan, draft Gain Plan, and landscape details are to be submitted to the LPA for consideration, making clear reference to the scale and significance of any change(s)
Implications for planning applications that have been approved prior to publication of the LNRS where the LNRS is published before submission of the gain plan

On and off-site baseline biodiversity values:

  • there is no need to reassess the baseline values as these are taken at the time the application is submitted

On and off-site post-development biodiversity values:

  • the strategic significance multiplier applied to the post development habitats must be reassessed following the guidance in the latest version of the Statutory Biodiversity Metric User Guide, together with the published Cumbria LNRS.

What publication of the LNRS means for new non-exempt applications

If an LNRS has already been published, then new, non-exempt applications submitted following publication must:

  • mark the strategic significance multiplier as ‘Low’ for all on and off-site baseline habitats
  • mark the strategic significance multiplier as ‘High’ for post-development habitats that meet the criteria within Table 7, page 28 of the Biodiversity Metric User Guide (habitats are to be marked 'Low' if they do not meet the criteria)

The ‘Medium’ multiplier category is not to be used if there is a published LNRS.

Biodiversity Gain Plan

Submission and decision process for a Biodiversity Gain Plan

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

A developer must submit the Biodiversity Gain Plan to the planning authority in writing, no earlier than the day after planning permission has been granted. 

Developers are strongly encouraged to bring together the required information into one document for approval. The Department for Environment, Food and Rural Affairs (DEFRA) have issued a Biodiversity Gain Plan template. 

The planning authority has eight weeks to approve the gain plan (unless another timescale is agreed).

Content of a Biodiversity Gain Plan for non-phased development

The following basic information must be included in a Biodiversity Gain Plan under paragraph 14(2) of Schedule 7A of the Town and Country Planning Act 1990:

information about the steps taken or to be taken to minimise the adverse effect of the development on the

  • biodiversity of the onsite habitat and any other habitat
  • the pre-development biodiversity value of the onsite habitat
  • the post-development biodiversity value of the onsite habitat
  • any registered off-site biodiversity gain allocated to the development and the biodiversity
  • any biodiversity credits purchased for the development

In addition, under Articles 37C(2) and 37C(4) of The Town and Country Planning (Development Management Procedure) (England) Order 2015, the following information must be provided:

  • name and address of the person completing the plan, and (if different) the person submitting the plan
  • a description of the development and planning permission reference number to which the plan relates
    pre-development and post-development plans showing the location of onsite habitat (including any irreplaceable habitat) on the relevant date, and drawn to an identified scale and showing the direction of north
  • the relevant date, for the purposes of calculating the pre-development biodiversity value of onsite habitats and if proposing an earlier date, the reasons for using this earlier date
  • the completed biodiversity metric calculation tool(s), stating the publication date of the tool(s), and showing the calculation of the pre-development onsite value on the relevant date, and post-development biodiversity value
  • description of arrangements for the maintenance and monitoring of any significant onsite habitat enhancements
  • a description of how the Biodiversity Gain Hierarchy will be followed and where to the extent one or more actions in that hierarchy are not followed, the reasons if not (except for irreplaceable habitats)
  • description of any irreplaceable habitat on the land to which the plan relates which exist on the relevant date, and any part of the development for which planning permission is granted where the onsite habitat of that part is irreplaceable habitat arrangements for compensation for any impact the development has on the biodiversity of the irreplaceable habitat

If habitat degradation has taken place, the following must also be provided:

  • a statement to this effect
  • the date immediately before the degradation activity
  • the completed biodiversity tool showing the calculation of the biodiversity value of the onsite habitat on that date
  • any available supporting evidence for the value

Content of a Biodiversity Gain Plan for a phased development

The Biodiversity Gain (Town and Country Planning) (Modifications and Amendments) (England) Regulations 2024 modifies the general biodiversity condition for planning permissions which are phased development. Instead of the standard approach for the Biodiversity Gain Plan:   

  • an Overall Biodiversity Gain Plan must be submitted to and approved by the planning authority before any development can begin
  • a Phase Biodiversity Gain Plan for each phase must be submitted to and approved by the planning authority before the development of that phase can begin

Content of an Overall Biodiversity Gain Plan

The Overall Biodiversity Gain Plan for a phased development (which is not related to a section 73 permission) must include the following matters:   

  • information about the steps taken or to be taken to minimise the adverse effect of the development on the biodiversity of the onsite habitat and any other habitat
  • the pre-development biodiversity value of the onsite habitat
  • any registered offsite biodiversity gain allocated or proposed to be allocated to the entire development and the biodiversity value of that gain in relation to the development
  • any biodiversity credits purchased or proposed to be purchased for the entire development
  • the post-development biodiversity value of the onsite habitat for the entire development and each phase of development

The post-development biodiversity value of the onsite habitat for the entire development and each phase is a projection of the biodiversity value at the completion of the entire development (not after the completion of each phase). 

Where firm proposals for development and habitat enhancement on each phase have yet to be finalised, assumptions about the likely development and habitat enhancements should be used to determine this post-development value. This value will set the expectations about the biodiversity value of onsite habitats, and the final value will need to be set out in later Phase Biodiversity Gain Plans. 

The Overall Biodiversity Gain Plan must also include the following further information:

  • name and address of the person completing the plan, and (if different) the person submitting the plan
    a description of the development and planning permission reference number to which the plan relates
  • pre-development plans showing the location of onsite habitat (including any irreplaceable habitat) on the relevant date, and drawn to an identified scale and showing the direction of north
  • the relevant date, for the purposes of calculating the pre-development biodiversity value of onsite habitats and if proposing an earlier date, the reasons for using this earlier date
  • the completed biodiversity metric calculation tool(s), stating the publication date of the tool(s), and showing the calculation of the pre-development onsite value on the relevant date, and post-development biodiversity value
  • description of arrangements for the maintenance and monitoring of any significant onsite habitat enhancements
  • a description of how the Biodiversity Gain Hierarchy will be followed and where to the extent one or more actions in that hierarchy are not followed, the reasons if not (except for irreplaceable habitats)
  • a description of any irreplaceable habitat on the land to which the plan relates which exist on the relevant date, and any part of the development for which planning permission is granted where the onsite habitat of that part is irreplaceable habitat arrangements for compensation for any impact the development has on the biodiversity of the irreplaceable habitat

If habitat degradation has taken place, the following must also be provided:

  • a statement to this effect
  • the date immediately before the degradation activity
  • the completed biodiversity tool showing the calculation of the biodiversity value of the onsite habitat on that date
  • any available supporting evidence for the value

Content of a Phase Biodiversity Gain Plan

The Phase plan focusses on that particular phase’s contribution to biodiversity net gain and confirming progress towards the overall biodiversity gain objective for the entire development. It must include the following matters:   

  • the post-development biodiversity value of the onsite habitat for the phase of the development which is the subject of the plan
  • the post-development biodiversity value of the onsite habitat for each other phase of development whether begun or otherwise
  • any registered offsite biodiversity gain allocated to the entire development and the biodiversity value of that gain for the development prior to submission of the phase plan
  • any registered offsite biodiversity gain which is proposed to be allocated to the entire development and the biodiversity value of that gain in relation to the development
  • any biodiversity credits purchased for the entire development prior to submission of the phase plan
  • any biodiversity credits proposed to be purchased for the entire development

The Phase Biodiversity Gain Plan must also include the following further information:

  • name and address of the person completing, and (if different) the person submitting the plan
  • description of the development and planning permission reference number which is relevant to the phase of development
  • post-development plans for the phase of development showing the location of existing onsite habitat (including any irreplaceable habitats) and drawn to an identified scale and showing the direction of north
  • completed biodiversity metric calculation tool(s) stating the publication date of the biodiversity metric used and showing the calculation of the pre-development and post-development biodiversity values
  • information about the steps taken or to be taken to minimise the adverse effect of the phase of development on the biodiversity of the onsite habitat
  • description of arrangements for the maintenance and monitoring of any significant onsite habitat enhancements
  • a description of how the Biodiversity Gain Hierarchy will be followed and where to the extent any actions in that hierarchy are not followed, the reasons if not (except for irreplaceable habitats)
  • a description of any irreplaceable habitat on the land to which the plan relates which exist on the relevant date, and any part of the development for which planning permission is granted where the onsite habitat of that part is irreplaceable habitat arrangements for compensation for any impact the development has on the biodiversity of the irreplaceable habitat

Other key principles and rules

The mitigation hierarchy

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.

You should have regard to the rules and principles set out in the current version of the biodiversity metric user guide as these will be used to assess biodiversity statements and gain plans.

Where evidence is required to demonstrate compliance with the metric rules and principles (for example evidence of competency) this is provided within the biodiversity statement and/or gain plan.

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.

Other statutory legislation

Statutory obligations in relation to biodiversity include compliance with legislation relating to the protection of site, protection of species and preventing the spread of invasive non-native species including. The main legislation being:

  • the Conservation of Habitats and Species Regulations 2017 (as amended)
  • Wildlife and Countryside Act 1981 (as amended).

Advance site clearance

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.

This is mandated within Schedule 14 of the Environment Act where 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.

Guidance and advice

Further information on BNG is available from: