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Definition of Biodiversity Net Gain

Biodiversity Net Gain is the principle of ensuring biodiversity will be in a measurably better state after new development has happened than before the development has taken place.

Implementing Biodiversity Net Gain

The Biodiversity Net Gain is now mandatory and required on all new planning applications which are not exempt. Applications are exempt if:

  • A development that does not impact a priority habitat and impacts less than: 
    • 25 square metres (5m by 5m) of on-site habitat 
    • 5 metres of on-site linear habitats such as hedgerows

A development 'impacts' a habitat if it decreases the biodiversity value.

It includes, for example, small projects like home extensions, conservatories or loft conversions.

  • An exemption applies to this type of development when it meets all the following conditions:  

Requirements for planning application

How to go through the Biodiversity Net Gain process:

Application and assessment

You must complete the latest version of the Biodiversity Metric or Small Sites Metric spreadsheet and submit this within your planning application. At the application stage we only need the baseline information for the site. Our Technical Officer will initially check this and:

  • Provide feedback if the documentation is incomplete or does not meet minimum standards and request resubmission
  • Request further information if deemed necessary
  • Pass correct documentation through to our assessment stage

During the assessment stage, a Planning Officer and a Wildlife Officer will review the documentation for approval / refusal. If the application has not been formally determined, you can still review and amend the active application.

Post-determination and post-development

Once approved, a condition will be attached to the planning application requiring the submission of a Biodiversity Gain Plan and other associated documents as required. This plan will describe how the 10% uplift in biodiversity will be achieved and must include the following information:

  • (a) 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
  • (b) The pre-development biodiversity value of the onsite habitat
  • (c) The post-development biodiversity value of the onsite habitat
  • (d) Any registered offsite biodiversity gain allocated to the development and the biodiversity value of that gain in relation to the development
  • (e) Any biodiversity credits purchased for the development
  • (f) Such other matters as the Secretary of State may by regulations specify

A Biodiversity Gain Plan template can be found on the Biodiversity Net Gain government website.

You may also have a post-development requirement for monitoring and providing survey reports to the Local Planning Authority.

We will monitor commitments within the documentation, any conditions attached from assessment stage, and your purchase of credits.

If the development has significant onsite biodiversity creation, we may be required to create a post-development monitoring schedule.

Providing documentation with your application

All planning applications which are not exempt from Biodiversity Net Gain will be required to submit documents describing the baseline biodiversity of the site. Further information on what needs to be submitted can be found on the Biodiversity Net Gain government website.

View the Biodiversity Metric documents on the Natural England website.

These documents will describe how the proposed application will impact the existing baseline level of biodiversity and how a 10% net gain in biodiversity will be achieved.

You may require an ecologist to produce the above documentation. It should be assumed that all major applications will require ecological input, and most minor applications.

Visit the Chartered Institute of Ecology and Environmental Management (CIEEM) website to find an ecologist.

If a 10% net gain cannot be achieved on site, then the required biodiversity units as defined by the Biodiversity Metric Calculation will have to be sourced and / or purchased from an area outside of the red line boundary, either owned by the applicant or owned by a third-party.

We can provide a list of off-site Biodiversity Unit Providers which have been registered on our system on request. Please note that other providers may exist.

If required, proof of purchase or agreement of the biodiversity units will be needed as part of the application or secured as a condition.

Registration for Biodiversity Unit Providers

Biodiversity Units are a proxy to describe biodiversity. There are three types of Biodiversity Units:

  • Area Units
  • Hedgerow Units
  • Watercourse Units

These are calculated in separate 'modules' of the Statutory Biodiversity Metric.

Landowners interested in using land to produce Biodiversity Units to sell to applications that require offsite units can register interest using our online form.

Registering interest will help the council match offsite units with developments in requirement of units.

The GOV.UK website will open a countrywide mandatory register for sites producing Biodiversity Units.

Further information

You can find further information about Biodiversity Net Gain on the following sites: