What is the direction of travel for the roll out of BNG for NSIPs?

In this update, we consider the implications of the Government’s response to the consultation on the implementation of biodiversity net gain for nationally significant infrastructure projects, published on 15 April 2026.

The Department for Environment Food and Rural Affairs (DEFRA) has published its response to the consultation (Consultation) on the implementation of biodiversity net gain (BNG) for nationally significant infrastructure projects (NSIPs) in England, which was launched in May 2025.

Burges Salmon assisted a number of clients in submitting responses to this consultation. It is encouraging that DEFRA appears to have responded positively to developer concerns regarding the application of BNG to NSIPs. For example, there are key changes that have been made regarding the land within the Order limits that will be subject to BNG, as well as concessions regarding temporarily impacted land. Further guidance will be issued by the Government in due course, but the consultation response gives a strong indication of what the BNG framework will look like for NSIPs. We have summarised the main talking points below.

Biodiversity Gain Objective

The biodiversity gain objective requires that the biodiversity value attributable to a development must exceed the pre-development biodiversity value of the on-site habitat by at least 10%. This is referred to as 10% BNG in the DEFRA consultation materials and model biodiversity gain statement.

This objective will be applied equally to all NSIPs through biodiversity gain statements which DEFRA will publish in May 2026 and will likely take the form of the model biodiversity gain statement at Annex 1 of the consultation response.. The objective will be applied to any NSIP project that submits its DCO application on or after 2 November 2026.

Applicants must continue to apply the mitigation hierarchy in relation to BNG which seeks to avoid harm in the first instance, before looking to reduce harm and then provide compensation.

Spatial Risk Multiplier

In delivering BNG, developers can provide on-site or off-site without a policy weighting in favour of either, subject to the application of the specific spatial risk multiplier for NSIPs. This is different to the TCPA regime which puts weighting in favour of on-site mitigation.

DEFRA have committed to providing guidance on the application of the spatial risk multiplier as it relates to NSIPs. Put simply, NSIPs will not incur a spatial risk multiplier in relation to the provision of off-site BNG from any local planning authority, national character area, or marine plan area that the NSIP BNG Boundary is located within. This ensures that the NSIP development is taken as a whole rather than encouraging, in the case of linear developments, modulation or partition of BNG across a scheme which would have the perverse effect of disincentivising larger scale mitigation projects rather than delivering better results for nature. There is an exception to this relaxation in relation to watercourse units, where DEFRA will not be changing how the spatial risk multiplier applies to watercourse units where a project spans multiple catchment areas.

It should also be noted that the relevant boundaries for the purpose of the spatial risk multiplier, which are currently the local planning authority, national character area and marine plan area boundaries, are proposed to be amended. The longer term aim is to use Local Nature Recovery Strategy boundaries which are considered a larger, more consistent unit.

The most significant movement in the proposed approach is that the baseline calculation for BNG will now be calculated in relation only to the land that will be negatively impacted by the development through the temporary or permanent deterioration or loss of habitats. Therefore, any land included within a project’s Order limits which is not subject to any proposed works will not need to be included in its BNG baseline. This will be especially helpful for linear projects including elements such as pipelines and cables, where often a wider corridor is included within the Order limits than is actually required for works in order to allow for micro-siting post-consent.

BNG Boundary Plan

A new concept in the BNG regime of the “BNG Boundary Plan” is proposed for NSIPs, This plan must be provided alongside an Outline Biodiversity Gain Plan at submission of a DCO application. The BNG Boundary Plan should show the entire Order limits and then overlay the BNG boundary within it, and then subdivide into areas that will be negatively impacted, areas that provide BNG, unimpacted habitat that has been included in the BNG boundary (retained habitat), and unimpacted habitat within the Order limits that is excluded from the BNG boundary and baseline. This retains the concept of providing 10% BNG over land which is being used to provide BNG.

Land subject to temporary impacts which is then reinstated will be considered “retained habitat” for the purposes of the statutory metric and is not subject to the same requirements to secure the management and monitoring of the habitat. Under the TCPA regime, the retained habitat concept currently applies where habitat can be reinstated within 2 years of impact. This has been extended to 5 years in the case of NSIPs, but this may not be sufficient for some longer linear schemes or significant schemes with long construction periods.

Some NSIPs will have areas of their Order land where there may not be an impacted habitat, and on that basis, this land can be excluded from the baseline. This suggests a pragmatic approach has been taken by the Government, as the 10% gain would not be required to be provided for unimpacted land that is not retained land.

The BNG Boundary Plan will need to be drafted along the same assumptions as a supporting environmental statement, being the realistic worst-case scenario based on maximum design and construction parameters (i.e adopting the Rochdale Envelope approach).

The BNG Boundary Plan is required to be submitted in outline, with the option to update the plan and calculations as part of the final approved biodiversity gain plan. It is important to note that the final provision of BNG needs to be calculated in respect of habitat value as at the time of submission of the final biodiversity gain plan.

Surveys and Delivery

Surveys informing the baseline must be collected within an “appropriate timeframe” prior to the application and then again for the updated biodiversity gain plan during the discharge of requirements. Where it is not possible to obtain access and there is insufficient alternative evidence, then ecologists must assume that the land supports the highest biodiversity value that can be reasonably supported. There will be an onus on the applicant to update surveys as part of the submission of the biodiversity gain plan. There is flexibility in the system that is being introduced in respect of changes, with an option for BNG mitigation to be secured after the submission of the gain plan in the case of any deficit identified at a later stage.

Outline biodiversity gain plan

Applicants must submit an outline biodiversity gain plan as part of their application packet. The purpose of this plan is to demonstrate a “strategy” for how the biodiversity gain objective of 10% will be achieved in relation to the application.

DEFRA’s biodiversity gain statement includes a 13 point list on what must be achieved in relation to the outline biodiversity gain plan. This includes a statement outlining the role and input of qualified ecological professionals. Elsewhere in the biodiversity gain statement and consultation response it is clear that qualified ecologists are expected to complete the statutory gain metric. This supports the need for project teams to ensure that appropriately qualified persons are overseeing the BNG documentation, and keeping appropriate records of this.

There is a requirement for the qualified ecologist to provide a statement that the baseline reflects the habitat as at the date of submission or if earlier, a justification for proposing that earlier date. This may require projects to compile survey data over multiple seasons which could be an additional burden for schemes with significant linear boundaries There is the option to agree an earlier date and DEFRA have confirmed that it will “issue guidance to encourage proportionate evidence requirements for agreeing an earlier date where needed”. Currently the biodiversity gain statement provides that an earlier date should be discussed and agreed with the Examining Authority and Secretary of State if unauthorised activities have taken place, or known permitted activities have not yet taken place. There is no specific mention of difficulties in relation to surveys.

The outline biodiversity gain plan will be supported by the BNG Boundary Plan, completed biodiversity metric calculations, and the proposed post-development biodiversity value. This includes the requirement for phasing details, where there is an intention to submit biodiversity gain plans on a phased basis. Where onsite gains are to be secured by a DCO requirement, then a draft habitat management and monitoring plan must also be provided.

Finally, the outline biodiversity gain plan should cover a strategy setting out how all final gains are intended to be secured before the operation of the project at the latest. This demonstrates that there is no requirement for gains to be secured prior to submission or consent or otherwise. The outline plan will also need to describe any uncertainty in the proposals, and demonstrate how the applicant can adapt to that uncertainty.

DCO Requirements

DEFRA have not provided a standard DCO requirement, but have set out the key operations of the DCO requirement being that the DCO should secure an updated biodiversity gain plan that must be submitted prior to commencement of development, which should include an updated metric calculation, evidence setting out how BNG is secured, detail of the changes since the outline plan, a strategy to secure any remaining biodiversity units and any other matters identified in the outline plan. This plan can be secured in phases.

The final biodiversity gain plan should include the submission of a final habitat management and monitoring plan, and secure that habitats are managed and maintained for at least 30 years from the habitat creation. Note here that DEFRA have included statements if the lifespan of the project is longer than 30 years, that the habitat should be generally maintained for this remaining period, presenting a potential for extension to the applicable BNG period.

The habitat management and monitoring plan should be updated to reflect changes made to any biodiversity gain plan. It is important to note that the final provision of BNG needs to be calculated in respect of habitat value as at the time of submission of the final biodiversity gain plan. This means that the outline plans provided at submission will always be a temporary, draft position. There will therefore be an onus on the applicant to update surveys as part of the submission of the biodiversity gain plan. Careful thought will need to given to land management practices between first survey and submission of the final plan. There is flexibility in the system that has been introduced in respect of changes, with an option for BNG mitigation to be secured after the submission of this gain plan in the case of any deficit identified at a later stage.

The DCO will also need to secure that any shortfall in BNG must be calculated and the deficit secured prior to operation of the project.

The relevant discharging authority can be any local planning authority within the Order limits or a single lead local planning authority where there are multiple hosts. Alternatively, the Secretary of State may be the discharging authority in consultation with relevant planning authorities. This may come as welcome news for linear projects as it would avoid the need for multiple plans being approved across the route of the project where the project extends across local planning authority areas.

Compulsory Acquisition

In the consultation, DEFRA had included some statements regarding the use of compulsory acquisition for BNG. DEFRA have now confirmed that there will not be any additional policy weighting regarding compulsory acquisition formalised in the biodiversity gain statement due to the existing process and guidance providing sufficient controls over the appropriate use of compulsory acquisition.

Conclusion

In response to the Consultation, the Government has amended its proposed method and approach to BNG for NSIPs. While not all suggestions made by developers have been taken forward, the changes clearly point to the Government seeking to adjust the principles of BNG established under the Town and Country Planning Act 1990 regime to the particular complexities of the NSIP system.

Our team regularly advises on BNG across the TCPA and NSIP regimes, so please contact Cathryn Tracey, Jen Ashwell or Douglas Haycock if you have any queries.