Biodiversity net gain - BNG - is a process by which development or land management aims to leave the natural environment in a measurably better state than it was prior to the development or management action taking place.

Under the Environment Act 2021 and its associated Statutory Instruments (Regulations), it is now mandatory for most major developments, and for many smaller developments, to achieve a minimum of 10% net gain. This is measured using a standardised metric calculation undertaken by a competent person, and is based upon the on-site habitats present pre-development, and those that are to be created or enhanced.

One of the main principles of BNG is the importance of the balance between the need for development and the natural environment. BNG requires the developer to either incorporate additional habitat spaces, or mitigate the loss by providing it elsewhere.

BNG does not replace the mitigation hierarchy of  avoid – minimise – mitigate – compensate.

Please see government guidance for details of how to prepare a metric.

Find out about:

• the biodiversity gain condition
• exemptions
• information requirements
• phased developments
• strategic significance
• off-site biodiversity net gain
• discharging the biodiversity gain condition
• monitoring, reporting and enforcement

The 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 general biodiversity gain condition ('the condition').

The condition has a separate legal basis in contrast to other planning conditions and will apply to all planning permissions, unless exempt. It will not appear on the decision notice along with the list of planning conditions imposed on the application, but will instead be referenced in an informative note.

The 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. More information on how to discharge the biodiversity gain condition is provided below.

Exemptions 

Planning applications that are exempt from requiring mandatory BNG include (but are not limited to):

• s73 applications for planning applications approved prior to BNG becoming mandatory
• householder applications
• permitted development
• de-minimis applications – those that have an impact on an area of habitat below 25m² (such as 5m x 5m) and below 5m in length for linear habitats, and do not affect priority habitat at all
• certain self-build and custom-build applications

For a full list and explanation of exemptions to mandatory BNG see biodiversity net gain: exempt developments.

If habitats are deemed to have been degraded before submission (or even after submission but prior to determination) then aerial photos (or other available evidence) will be used to decide the habitat type and an assumption of the highest scoring condition category applied within the biodiversity metric.     

Information requirements

Chesterfield Borough Council advises that all applicants enter into pre-application discussions prior to submitting an application. These discussions will help to determine the potential impact of a development and help to determine the scope of surveys and assessments required to support an application. Please see our page on pre-application advice for more information. 

The list below 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.

 Applicants should also submit the following at the earliest possible stage:

• 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

The main metric should be completed by a competent person has the knowledge and skills to perform specified tasks to complete and review biodiversity metric calculations. You obtain this through training, qualifications, experience, or a combination of these. Competency is aligned with the British Standard ‘process for designing and implementing biodiversity net gain (BS 8683:202).

If a river condition assessment is required as part of completing the metric, this must be completed by a qualified assessor.

Phased developments

Phased development must meet the biodiversity gain objective of at least 10% net gain across the entire development (unless it is exempt or subject to transitional arrangements) and the requirement for the Biodiversity Gain Plan differs.

An overall Biodiversity Gain Plan is required to set a clear upfront framework for how the biodiversity gain objective will 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.

Detailed guidance on how BNG is approached for phased development is available in the BNG planning practice guidance, including biodiversity gain templates.

Strategic significance

Spatial multipliers are used to influence metric calculations to take account of whether pre- and post-development habitats are located in ecologically significant areas, and termed ‘Strategic Significance’. Prior to the production and adoption of the Local Nature Recovery Strategy (LNRS), the following are considered to be strategically significant:

• sites of special scientific interest (SSSI)
• local nature reserves, local wildlife sites
• open space network (as defined in the Local Plan)
• ecological networks (as defined in the Chesterfield Greenprint)

Where habitats cross boundaries between areas of different strategic significance, the habitat parcel should be split.

The local nature recovery strategy (LNRS) for Derbyshire is currently in production and details of the ongoing process, collaborations, consultations and the outcomes for this are provided on Derbyshire County Council website.

Off-site biodiversity net gain

Where a development cannot meet the biodiversity gain objective through on-site actions alone, then off-site 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. Find more information on what is involved in entering a legal agreement to secure off-site biodiversity net gains.

Habitat banks

At this time Chesterfield Borough Council is not registered as a responsible body and is not able to offer a habitat bank regulation service. Where off-site habitats are required (and / or significant on-site habitats), this will need to be secured through a s106 planning obligation, or a conservation covenant with a responsible body identified by the applicant requiring the off-site gains.

The legal agreement securing appropriate management of habitats must last at least 30 years from finishing the habitat improvement. If securing:

• on-site gains, the legal agreement starts from the date the development is completed
• off-site gains, the legal agreement starts from the date the habitat enhancement is finished

The length of time it will take to create or enhance the habitat (for example, one year) must also be included, as this will inform an accurate end date for the legal agreement.

Chesterfield Borough Council will work with applicants to establish the defined point of development completion for when the period of at least 30 years begins, which will include completion of on-site habitat enhancement and not just completion of built structures, or issue of a building regulations notice.

This requirement is set out in PPG Paragraph 022 Reference ID: 74-022-20240214 of the biodiversity net gain guidance.

Statutory credits

If it isn’t possible to provide biodiversity improvement on or off the site, it will be possible to buy ‘credits’ from the government. This would need to be explained as part of the planning application process. More information about credits is available from the Gov.uk website. 

Discharging the 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.

What to submit

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. The final Biodiversity Gain Plan 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.

Irreplaceable habitats

If the on-site 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

Monitoring, reporting and enforcement

Under mandatory BNG, all habitats must be managed for 30 years starting from the completion of development. 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 on-site enhancements, as well as off-site habitats to be monitored so that management strategies can respond and adapt if necessary.

It is mandatory for the outcomes of this monitoring to be reported to the local planning authority (LPA) (in the case of habitats secured through planning conditions or obligations), or the responsible body (in the case of habitats secured through conservation covenants) so that these bodies can undertake subsequent mandatory reporting to central government on delivery of BNG and local outcomes.

The frequency of monitoring and reporting will be agreed based on the habitats involved and the complexity of the site. Monitoring reports 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 (and therefore biodiversity unit) delivery not be progressing as agreed via the approved Biodiversity Gain Plan, the LPA (or responsible body for habitats secured through conservation covenants) will have powers of enforcement. 

Useful links

There is a large amount of information available online from the government (specifically the Ministry of Housing, Communities and Local Government and Defra).

Some useful links are provided below:

• meet biodiversity net gain requirements: steps for developers
• biodiversity net gain information
• biodiversity net gain planning practice guidance

The Planning Advisory Service has published guidance for local planning authorities (LPAs) which may also be of interest.