Biodiversity Net Gain (BNG) is an approach to development that seeks to leave the natural environment in a measurably better state than it was before development occurred.

The way the planning system considers its impacts on biodiversity has changed. Starting in 2024, new statutory regulations mean that, subject to some exemptions, development will have to demonstrate a minimum 10% increase in biodiversity.

When does BNG Apply?

BNG became a mandatory requirement for major development on the 12 February 2024. For Minor development, BNG came into force from April 2 2024.

Exemptions

While BNG applies to the majority of planning applications, the following types of development are exempt from the BNG requirements:

• Householder applications
• Permitted development
• Applications subject to the ‘de-minimis’ threshold where the development does not impact a priority habitat, and it impacts less than, 25m² of habitat, and/or less than 5m of a linear habitat
• Existing applications submitted prior to the 12 February (for majors) or 2 April 2024 (for minors)
• Self-build and custom build development which:
• consists of no more than 9 dwellings, and
• is carried out on a site which has an area no larger than 0.5 hectares, and
• consists exclusively of dwellings which are self-build or custom housebuilding as defined in section 1(A1) of the Self-build and Custom Housebuilding Act 2015.
• Urgent Crown development
• Development of a biodiversity gain site
• Development related to the high speed railway transport network. 

The full details of BNG exemptions are set out in the Biodiversity Gain Requirements (Exemptions) Regulations 2024 and in Government Guidance.

The Biodiversity Net Gain Process

The General Biodiversity Gain Condition

The Town and Country Planning Act has been amended to make every grant of planning permission deemed to have been granted subject to the following General Biodiversity Gain Condition:

The development may not be begun unless:

(a) a Biodiversity Gain Plan has been submitted to the planning authority; and

(b) the planning authority has approved the plan.

The purpose of the General Biodiversity Gain Condition is to secure the ‘Biodiversity Objective’, which requires the post-development biodiversity value to exceed the pre-development biodiversity value of the on-site habitat by at least 10%.

Biodiversity net gain can be achieved through habitat creation or enhancement on-site or off-site; the purchase of biodiversity units from a habitat bank; or as a last resort through the purchase of statutory credits; or a mixture of these.

Preparation of Biodiversity Net Gain Reports

Planning applications subject to BNG need to submit a report and metric calculation that record the biodiversity value of the site prior to development taking place and predict what the value of the site will be after development. These reports are usually prepared by an ecologist.

The Council’s Biodiversity Net Gain SPD previously provided information on how to assign strategic significance within BNG calculations prior to mandatory net gain coming into force. Since the publication of the SPD, new guidance has been provided in Table 8 of the Statutory Metric User Guide, that sets out how strategic significance values should be assigned where the Local Nature Recovery Strategy has not yet been published. City of Doncaster Council has therefore published revised guidance on this topic - Planning Policy Guidance: Assigning Strategic Significance for applications subject to mandatory Biodiversity Net Gain.

Planning Policy Guidance: Assigning Strategic Significance

Applications subject to mandatory net gain should follow this guidance in carrying out their net gain calculations. (Applications submitted prior to mandatory Net Gain coming into force can use either the guidance above or that previously published in the SPD.)

Submission and Assessment of an Application

The Planning Practice Guidance (PPG) makes it clear that, when assessing an application, the Council needs to be confident that the Biodiversity Objective is able to be met prior to determining the application. So, although biodiversity net gain is a pre-commencement condition, it must be considered throughout the planning process and cannot be left until post-determination.

Validation of Applications

The Planning Application form sets out the minimum level of information in relation to biodiversity net gain that must be provided to the Council for an application to be validated.

The Council is in the process of updating its local validation checklist to include the submission of a Biodiversity Net Gain Statement. This will require information such as:

• the details of what biodiversity will be delivered onsite post development (or an estimate of that for outline applications),
• steps taken to minimise adverse biodiversity impacts in line with the mitigation hierarchy and Biodiversity Gain Hierarchy,
• the proposed strategy for meeting the Biodiversity Gain Condition, including the anticipated balance between onsite units, offsite units and statutory credits,
• details of any significant onsite enhancements and a draft habitat management and monitoring plan to secure those.

Significant Onsite Enhancements

Planning Policy Guidance on Defining significant on-site enhancements for Biodiversity Net Gain has been published by City of Doncaster Council. This sets out what the Council consider represents 'significant enhancements' within development proposals, and therefore what elements of the proposed on-site biodiversity net gain that it expects to be delivered and monitored for at least 30 years.

Planning Policy Guidance: Defining Significant onsite enhancements

Should significant on-site habitat need to be secured through a S106 planning obligation, this will need to be completed and signed prior to the planning permission being issued.

Offsite Biodiversity

Where a development cannot meet the Biodiversity Gain Objective through onsite actions alone, then offsite biodiversity units will need to be secured. These can be bought on the open market from a Habitat Bank, through a bespoke scheme for an individual development, or via the purchase of Statutory Biodiversity Credits from central government. Where the applicant wants to use a bespoke scheme, then this will need to be legally secured with a s106 agreement, so it is important that discussions with the Council about this take place as early as possible. There is more information on what is involved in entering a legal agreement to secure offsite biodiversity net gains on the UK GOV webpages.

The Decision Notice

The General Biodiversity Gain Condition has a separate legal basis in contrast to other planning conditions and will apply to all planning permissions, unless exempt. The General Biodiversity Gain Condition will therefore not appear on the decision notice along with the list of planning conditions imposed on the application, rather it will be referenced in an informative note.

The General Biodiversity Gain Condition cannot be varied or removed by an application under section 73 of the Town and Country Planning Act. It also cannot be discharged as part of the grant of planning permission.

Discharging the General Biodiversity Gain Condition

Following the grant of planning permission, a development cannot be commenced until the General Biodiversity Gain Condition has been successfully discharged. This requires a Biodiversity Gain Plan to be submitted to and approved by the Council.

Biodiversity Gain Plans

To discharge the General Biodiversity Gain Condition, a completed Biodiversity Gain Plan, which sets out how the Biodiversity Gain Objective of at least a 10% gain will be achieved, must be submitted to the Council along with the following supporting information:

• A completed statutory biodiversity metric;
• Pre-development and post-development plans showing the location of on-site habitat;
• A compensation Plan if the development affects irreplaceable habitats;
• Biodiversity Net Gain Register reference numbers if they’re using off-site units (purchased from a Habitat Bank);
• Proof of purchase if buying Statutory Biodiversity Credits;
• A Final Habitat Management and Monitoring Plan (HMMP) setting out how significant on-site gains will be managed and monitored.

The plan must be submitted in writing, no earlier than the day after planning permission has been granted. There is no separate application form to be completed, but there will be an additional statutory £145 fee. Final Biodiversity gain plans should be submitted citing the planning application reference to which it relates.

Published templates for the Biodiversity Gain Plan and the Habitat Management and Monitoring Plan have been created and should be used.

Biodiversity Gain Plans for Phased Development

Where development is to be delivered in phases, the requirement for biodiversity gain plans differs. Instead of the standard approach as detailed above:

An Overall Biodiversity Gain Plan must be submitted to and approved by the Council. Before any phase of development can start, a Biodiversity Gain Plan for that phase must be submitted to and approved by the Council.

This recognises that phased development can often be implemented over a long period of time. The purpose of the Overall Biodiversity Gain Plan is to set a clear upfront framework for how the biodiversity gain objective of at least a 10% gain is expected to be met across the entire development. The Biodiversity Gain Plan for each phase will then subsequently set out a phase’s contribution to biodiversity net gain and track progress towards the achieving the biodiversity gain objective.

Irreplaceable Habitats

If the onsite habitat includes irreplaceable habitat then the Biodiversity Gain Plan must include:

• Information about steps taken or to be taken to minimise any adverse effect of the development on the habitat.
• Information on arrangements for compensation for any impact the development has on the biodiversity of the irreplaceable habitat.

The Council can only approve a Biodiversity Gain Plan if satisfied that the adverse effect of the development on the biodiversity of the irreplaceable habitat are minimised and appropriate arrangements have been made for the purpose of compensating for any impact which do not include the use of biodiversity credits.

Monitoring

To ensure that habitats establish well and meet target condition within the timeframe provided in the final biodiversity metric calculations, it will be necessary for habitats considered significant onsite enhancements, as well as offsite habitats to be monitored so that management strategies can respond and adapt if necessary.

The frequency of monitoring and reporting will be agreed based on the habitats involved and the complexity of the site. Monitoring report must be submitted by whoever is responsible for managing the delivery of significant on-site habitats and all off-site habitats. A typical monitoring schedule would require surveys in years 1, 2, 5, 10, 15, 20, 25 and 30 following habitat creation or enhancement being completed. Should habitat delivery not be progress as agreed via the approved Biodiversity Gain Plan, the Council will have powers of enforcement.

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