Biodiversity Net Gain Frequently Asked Questions

• The actions taken to meet BNG obligations
• Details of biodiversity gains achieved or expected from approved biodiversity gain plans
• Planned actions for the next reporting period

The Biodiversity Gain Plan (BGP) is a document which sets out how a development will deliver biodiversity net gain and allows the planning authority to check whether the proposals meet the biodiversity gain objective. The legal requirement is for it to be submitted after planning consent has been granted.

The Environment Act sets out that development subject to mandatory BNG will be required to submit a biodiversity gain plan for planning authority approval, and the planning authority is required to approve it prior to commencement. This is required under the 'General condition of planning permission' added as Schedule 7A to the Town and Country Planning Act 1990 (under Schedule 14 of the Environment Act).

The PPG sets out the requirements when submitting a BGP, what must be included within the document and how to determine and approve a BGP. The guidance also offers additional information relating to appeals, BGP’s for phased developments and S73 permissions for phased developments.

On-site biodiversity net gain refers to the post-development biodiversity value of any on-site habitat within the red-line boundary of the proposed development site.  Please note this does not include land within the blue-line boundary (land outside the red-line boundary, but under the same ownership).  

Off-site biodiversity net gain refers to the post-development biodiversity value of any off-site habitat outside of the red-line boundary, regardless of land ownership. Any off-site biodiversity net gain should be formally registered on Natural England’s Gain Site Register and secured via a Conservation Covenant or planning obligation, i.e. Section 106 agreement. Any off-site ‘enhancements’ should be recorded on the gain site register, evidencing the ‘allocation’ of units required for the development under consideration.  

The applicant should follow the Biodiversity Gain Hierarchy (see the BNG PPG for further information). The Statutory Biodiversity Metric User Guide also provides further information on on-site and off-site biodiversity gain. Government Statutory biodiversity credits guidance states that if a developer needs less than 0.25 biodiversity units (area or linear), they can buy statutory credits without needing to provide evidence that insufficient off-site options are available.

Significant on-site BNG and off-site BNG components of the post-development biodiversity value must be secured for a minimum term of 30 years. This commitment must be legally secured in one of three ways:  

• As a condition attached to the planning permission (only for on-site gains),  
• Through a planning obligation, or  
• Through a conservation covenant.  

PAS has published Biodiversity Net Gain Legal Agreement & Planning Condition Templates for securing on- and off-site BNG. 

For off-site BNG, habitat enhancement works must be secured via planning obligation or conservation covenant to register the off-site gains. Both do not need to be in place to secure a site – just one of those two options. Both are equally valid legal mechanisms for securing habitat banks, paving the way for their registration on the net gain register. 

For on-site BNG, the habitat enhancement works need to be maintained for at least 30 years 'after the development is completed'. LPAs and developers should agree on how completion of development will be determined to give clarity on how long the onsite BNG will need to be maintained. This could be practical completion, first occupation, or some other trigger. 

For off-site BNG, the habitat enhancement will need to be maintained for at least 30 years from completion of the habitat creation or enhancement works. When negotiating with the applicant, planning officers should identify how ‘completion’ will be determined and when exactly the development or habitat enhancement works are to be completed to identify when exactly the management and monitoring term begins and ends, ensuring that this information is highlighted within key agreements. 

It is good practice to require a Habitat Management and Monitoring Plan (HMMP) as part of the condition, legal obligation or conservation covenant to set out details of how the land will be managed over at least 30 years. 

In some cases, for example where habitat is created or enhanced as mitigation for sites or species protected under the Habitats Regulations, the requirement may be for management and maintenance of habitats ‘in perpetuity’. It will be up to the planning authority to determine the length of time that it is appropriate and reasonable to require ongoing management and maintenance of habitats as part of the grant of planning permission, taking into account the range of policy and legislative requirements, but the legal requirement for biodiversity gain habitats is 30 years as a minimum. Defra’s combining environmental payments guidance covers biodiversity units and nutrient credits, alongside other environmental payments.

Under the mandatory BNG approach, biodiversity units refer to the output of the biodiversity metric. The metric uses habitats and ‘biodiversity units’ as a proxy to describe biodiversity. These biodiversity units are the ‘currency’ of the metric. There are three types of biodiversity units, which are calculated in three separate ‘modules’ of the metric (area units, hedgerow units and watercourse units). Off-site biodiversity units can be sold, i.e. ‘1 unit of modified grassland costs £xx', but should not be referred to as credits to avoid confusion with statutory credits. Statutory credits are the last resort option for developers, if they can’t deliver the BNG they need onsite or via purchasing off-site biodiversity units. See our Statutory Biodiversity Credits page for more information.

Habitat banking is an approach where investors pay landowners to increase the biodiversity value of their land and this uplift is then sold as units to those that need off-site biodiversity net gain. Often habitat is created in advance of units being sold meaning this is an ecologically beneficial approach. In practice, the term ‘habitat bank’ can either be used to describe:

• The parcel or parcels of land where the value of biodiversity is uplifted to provide off-site biodiversity units.
• The green finance approach where investors finance habitat restoration and creation and are rewarded with both monetary interest and environmental returns. See the Future Parks Accelerator resource for more information.

Under mandatory BNG, habitat created or enhanced after 30 January 2020 are eligible for registration and sale of the associated biodiversity gains, provided it meets the other criteria of the biodiversity gain site register. Further information on habitat banking and BNG is provided in Defra’s Sell biodiversity units as a land manager guidance.

A responsible body is an organisation designated by the Secretary of State under the Environment Act 2021 as able to enter into conservation covenant agreements with landowners in England. Their role includes ensuring the other party meets its requirements. For BNG, this role would include agreeing the Habitat Management and Monitoring Plan for an off-site gain site and receiving and acting upon subsequent monitoring reports from the landowner. 

Responsible bodies must be organisations for which at least some of their main purposes, functions or activities relate to conservation, and they must have the capability to take on the responsibility of the designation. Government maintains a list of current designated responsible bodies. Local authorities can apply to be designated as a responsible body. Natural England are referenced as a responsible body, but, to avoid any potential conflict of interest they do not offer conservation covenants for BNG.

Further information is available on our Responsible Bodies and Conservation Covenants webpage.

Only 'significant' on-site gains need to be secured for at least 30 years. PAS has published Biodiversity Net Gain Legal Agreement & Planning Condition Templates for securing on-site BNG. 

Government guidance for developers provides information on what counts as a ‘significant’ enhancement. Government guidance for LPAs highlights that in addition to minimum information requirements, further information may need to be provided with the planning application to support the consideration of BNG for significant on-site biodiversity enhancements, including a draft habitat management and monitoring plan as part of the application.

Schedule 7A Para 9 (b) of the Town and Country Planning Act 1990 (as updated by Schedule 14 of the Environment Act 2021) (which focuses on the post-development biodiversity value) states that 'significant' is based on what the relevant planning authority considers significant in relation to the pre-development biodiversity value.

Whether enhancement should be counted as significant depends on the scale of development and the baseline (pre-development) habitat on-site, but it will normally involve:

• Habitats of medium or higher distinctiveness,  
• Habitats of low distinctiveness that create a large number of biodiversity units relative to the biodiversity value of the site before development, or
• Areas of habitat creation/enhancement that are large relative to the size of the development.  

Significant enhancement is not just about number of units or area of habitat and will depend entirely on the context of the development site. The condition and distinctiveness of enhanced and created habitats will also influence the decision of whether the gain is to be classed as significant.  You may not be able to make a judgement on whether the gain is significant until post-consent. 

Retained habitats which already exist do not count as significant on-site enhancement, as significance is defined in reference to the pre-development value; these retained areas already exist and are being retained both in condition and distinctiveness, so there is no anticipated gain. The retention of on-site habitat does still contribute to the post-development biodiversity value. The Statutory Biodiversity Metric User Guide provides further information on habitat retention for area and hedgerow modules (Page 30). The user should only select habitat retention when there is no loss of habitat, the habitat is being kept in its baseline condition, and no action is being taken to enhance it. This section also notes that retained habitats may still require ongoing intervention to maintain their baseline condition, which indicates that any retained habitats that are part of a proposal where BNG is considered ‘significant’ should be maintained in the same condition, type and distinctiveness for at least 30 years.

While we are all still getting used to the BNG system, many LPAs are taking a cautious approach and, where there is doubt, putting the onus on the applicant to be clear and explain why the enhancement proposed on a development site isn't significant. LPAs are also determining their own definition of what counts as significant on-site BNG. 

Government guidance also provides information on non-significant BNG, habitat changes (as calculated within the biodiversity metric tool) whose loss will not significantly decrease the post-development biodiversity value.

A gain site is also commonly known as a habitat bank, biodiversity unit scheme and/or supply area. In the context of BNG, gain sites are areas which are registered biodiversity units supply areas on Natural England’s Gain Site Register. You can search for sites on the register here.  

Yes, they can. Several local authorities undertook assessments to evaluate the potential supply and demand for biodiversity units even before BNG became mandatory. Valuable learning across different parts of the country has enabled some LPAs to use their own land or assets for the purpose of generating and selling biodiversity units to local developments. 

The PAS Off-site BNG Marketplace webpage provides an overview of local authority interactions with the off-site BNG marketplace, including key insights on potential supply and demand for biodiversity units, regulating off-site proposals for the purpose of selling and supplying biodiversity units and working with Natural England’s Gain Site Register. 

A range of mechanisms have been, and continue to be, explored. The most notable include arm’s-length bodies such as special-purpose vehicles, intermediary environmental funds (often in the form of charitable bodies) to channel investment into public green spaces, and reciprocal arrangements - the choice of which often depends on the type of authority involved and local priorities.

It is important to note that, even for LPAs, any gain sites must be registered on Natural England’s Biodiversity Gain Site Register and must be legally secured for at least the minimum required term. Local authorities can not direct developers to purchase biodiversity units from them in preference to other ecologically equivalent suppliers, and will be expected to manage any associated conflicts of interest. 

Any approach to the delivery of BNG (for developments where it is mandatory) needs to meet the minimum requirements as set out in the legislation (primary and secondary). This means that LPAs are not be able to levy a tariff system (i.e. a general fee) to then pool money for investment in nature elsewhere at some future point. There is, however, scope to encourage the development of a local habitat bank (on LPA or other third party land) from which multiple developments secure BNG through a single site through the sale of smaller parcels of biodiversity unit uplift.

Defra’s guidance for local authorities on BNG provides further information on off-site gains on land owned by a local planning authority. Freeths have written an article on how local authorities can create habitat banking mechanisms for BNG.

Yes, they can. Many LPAs are in the process of developing, or have already produced their own monitoring fee matrices, which outline estimated fees based on anticipated monitoring time requirements. Current approaches typically consider the technical complexity of habitat creation or enhancement, as well as habitat distinctiveness. In some cases, LPAs have also developed supporting monitoring strategies to assist internal enforcement teams. 

The Statutory Biodiversity Metric User Guide (SBMUG) lists four fundamental rules that must be followed to claim a biodiversity net gain (Table 2).  

Rule 1 is that 'The trading rules of the biodiversity metric must be followed'. Trading rules require habitat loss to be compensated for on a like-for-like or like-for-better basis.  

Rule 2 states that biodiversity unit outputs, for each type of unit, must not be summed, traded, or converted between types. The requirement to deliver at least a 10% net gain applies to each type of unit.  

Rule 3 states that to accurately apply the biodiversity metric formula, you must use the statutory biodiversity metric calculation tool (SBM) or statutory biodiversity metric tool (SSM) for small sites. Although the SSM is restricted to small sites, users can still use the SBM for small sites.

Rule 4 is 'In exceptional ecological circumstances, deviation from this biodiversity metric methodology may be permitted by the relevant planning authority.'. A separate FAQ for Rule 4 can be found below. 

Further information is available on our Statutory Biodiversity Metric Rules webpage.

The Statutory Biodiversity Metric User Guide (SBMUG) lists four fundamental rules that must be followed to claim a biodiversity net gain (Table 2). Rule 4 is 'In exceptional ecological circumstances, deviation from this biodiversity metric methodology may be permitted by the relevant planning authority.'. This rule applies only in cases where there is a clear ecological justification that a proposal will deliver significant environmental benefits not fully captured by the metric tool. The decision to apply Rule 4 lies with the relevant planning authority and, in most cases, it will not be appropriate to use this rule. 

It is important to note that other metric rules still apply, even where Rule 4 is invoked. Rule 4 may be used to support proposals in specific circumstances, particularly where creating a proxy habitat could offer equivalent or enhanced ecological benefits to replace habitats that are difficult to recreate.

Further information on the appropriate use of Rule 4 is available on our Statutory Biodiversity Metric Rules webpage.

The Biodiversity Gain Requirement (Exemptions) Regulations 2024 set out exemptions to the mandatory biodiversity net gain (BNG) requirement. Further information on exempt developments is available in Government guidance and the BNG Planning Practice Guidance (PPG) and the PPG also covers what information LPAs should expect applicants to set out in their statement setting out the reasons why they believe the application is exempt. It is likely that evidence will need to be provided to support a de minimis exemption. Further information is provided on the de minimis exemption our Navigating Exemptions from Biodiversity Net Gain.

The BNG PPG sets out legal minimum information requirements at planning application stage and what additional information LPAs may wish to ask for. 

There has been a lot of useful debate within the PAS BNG practitioner network for LPA officers about what information (on top of the statutory minimum) could / or should be asked for at the validation stage as a local list, and there are 'minimum' and 'optional' versions of this. 

It really is one of those things that is up to each LPA and needs to be factored against the type, scale and nature of the development and the BNG requirement. LPAs need to set sensible, proportionate and justifiable local validation requirements and take an appropriate stance where these are not met - can the information be provided later, or is it so fundamental that the application can't be validated?

Schedule 14 of the Environment Act sets out that a general condition will be applied to every planning permission (except those developments which are exempt from the BNG requirement) that a biodiversity gain plan should be submitted and approved by the planning authority before commencement of development, specifically:

• Every planning permission granted for the development of land in England shall be... subject to the [following] condition: the development may not be begun unless a biodiversity gain plan has been submitted to the planning authority... and the planning authority has approved the plan...

This means that a complete biodiversity gain plan will be required for all relevant development. It is important to note that the biodiversity gain plan must be submitted before commencement of development, but can not be submitted before the grant of permission. The BNG PPG sets out more information on submission and approval of the biodiversity gain plan. 

The PPG (specifically paragraphs 025/026) contains suggested text for use on decision notices to help local planning authorities to comply with the requirements on BNG. The use of this suggested text is discretionary, and local planning authorities should make decisions on the content of their decision notices and may wish to get their own legal advice. 

Information on what is legally required at the planning application stage and what further information may be needed to assist the consideration of biodiversity net gain as part of the planning application is set out within the BNG PPG. The PPG also sets out how BNG should be taken into account in decision making. Approval of the biodiversity gain plan takes place after consent, but decision makers may need to consider more broadly whether the biodiversity gain condition is capable of being successfully discharged at planning determination stage. Defra guidance on 'BNG: what local planning authorities should do' also covers what LPAs should check before granting permission, including checking biodiversity metric calculations, and that LPAs may need to check habitat surveys.

As set out in Defra guidance on 'BNG: what local planning authorities should do', the LPA has a role in reviewing and checking the information provided in the statutory biodiversity metric calculation tool. 

LPAs are not not expected to assess the competency of the person who supplied it. If the application triggers the watercourse module for the statutory biodiversity metric tool, a qualified assessor is required to undertake the corresponding river condition assessment.  

LPAs should trust that the person supplying the habitat information has followed the associated user guides and has satisfied themselves that they are competent. If the LPA is in any doubt about the competency of the person providing the information, the LPA may request a ‘competency statement’ to support this. In this statement, the LPA may ask the user to set out what training, qualifications, or experience they have. Competency should not be used as a reason to ignore the advice of an ecologist where it may be justifiably required/given.

BNG does not change existing protections, so current legal and policy provisions relating to development impacts on the natural environment, including protected sites and species, and priority species and habitats, all need to be considered in relation to habitat loss. A development cannot avoid this requirement by virtue of delivering a net gain. If there are protected species on-site, then these should be approached and managed in the same way as they are currently. BNG requirements (and biodiversity metric calculations) would then be additional to this.

BNG just ensures that habitat is ‘valued’ in a way that it may not have been, and that is at least replaced with a 10% extra. Assuming the habitat lost is not irreplaceable and the project is otherwise permissible, an LPA could not refuse planning permission based solely on the lifespan of a replacement habitat. Ultimately, it is the LPA’s decision whether the biodiversity net gain information accompanying an application, and the subsequent biodiversity gain plan, is acceptable and whether to refuse or not on this basis, using the evidence submitted by the applicant, including on any locally distinctive habitats, to inform that decision.  The Biodiversity Metric Tool also considers the risk of delay to the creation/ enhancement of habitat; so, where a habitat is being lost and a new habitat is being created to replace it, this is more costly in terms of biodiversity units (and harder to reach 10%) than enhancement.  The LPA will need to be satisfied that the Biodiversity Metric has been used appropriately.

The Biodiversity Metric is a habitat-based approach, using habitat as a proxy for biodiversity. Species-based features such as bird and bat boxes are not included within the metric; instead, it focuses on the habitats that species need to forage and complete their life cycles. The provision of such species features within developments should still be encouraged, and LPAs can promote their usage through design guides and codes.