BNG for energy and infrastructure NSIPs: Navigating the new guidance ahead of 2 November 2026

Key points

• Biodiversity net gain (BNG) becomes mandatory for development consent order (DCO) applications made on or after 2 November 2026. Applications made before that date are not subject to the statutory requirement, even if examined and decided afterwards.
• Ten biodiversity gain statements have been published covering all nationally significant infrastructure project (NSIP) development, including for development where no national policy statement (NPS) has effect. The core obligation – a minimum 10% net gain in biodiversity value – is uniform across all sectors, with no sector-specific calculation or ecological nuance.
• On-site BNG must be legally secured – by a section 106 obligation, conservation covenant or DCO requirement – for at least 30 years from completion of the habitat enhancement works.
• A draft Habitat Management and Monitoring Plan (HMMP) must be submitted with the outline biodiversity gain plan at DCO application stage, meaning that ecological survey work and habitat management planning must be sufficiently advanced at the point of application.
• Excess on-site biodiversity gains exceeding the 10% requirement can be allocated as off-site gains for other developments.

Introduction

In May 2026, we reported that biodiversity net gain (BNG) will become mandatory for NSIPs on 2 November 2026 and identified a number of areas where detailed guidance was still awaited. On 2 June 2026, Defra delivered that guidance – publishing ten biodiversity gain statements and a substantial package of supporting materials on the Government's BNG for NSIPs collection page. What does this package of guidance mean in practice for NSIP developers with NSIP projects in the pipeline?

What do the ten biodiversity gain statements say – and how do they differ by sector?

The biodiversity gain statements set out the framework for calculating, evidencing, and verifying gains and will inform the BNG aspect of the examination and decision-making. Statements have now been issued for airports, data centres, energy, geological disposal infrastructure, hazardous waste, national networks, ports, waste water, water resources, and, notably a standalone statement for any NSIP where no NPS has effect (the "no-NPS" statement).

The ten statements are, in substance, a single template adapted by sector. The core BNG obligation – a minimum 10% net gain in biodiversity value, calculated using the statutory biodiversity metric and delivered through the on-site/off-site/statutory credits hierarchy – is identical across all ten. The principal variations are largely the statutory scope references or are otherwise cosmetic. There is no sector-specific BNG calculation or ecological nuance. 

When do the biodiversity gain statements take effect?

From 2 November 2026, the statements will have the same effect as if they were included in a NPS. It should be noted that a DCO application (including an application to make changes to a granted DCO) made before 2 November 2026 will not be subject to the 10% biodiversity gain objective, even if it is examined and decided after this date.

How does the updated metric treat temporary habitat losses for NSIPs?

Our May 2026 report flagged that the metric user guide would be updated to extend the rule allowing habitats temporarily impacted and restored within two years to be counted as retained, extending that period to five years for NSIPs. The updated Statutory Biodiversity Metric User Guide (here), confirms this NSIP-specific flexibility. 

The guide provides that, for NSIPs, habitats of low or very low distinctiveness that are temporarily impacted do not need to be recorded as lost provided the area can be restored to both baseline habitat type and baseline condition within five years of the initial impact, compared to the two-year period that applies to all other development types. 

Importantly, applicants should note that temporary losses treated as retained in the metric are still negatively impacted habitats and must be included in the baseline and BNG boundary. The concession reduces the recording burden but does not remove those habitats from the scope of BNG.

What must the BNG boundary plan include — and what can be excluded?

A BNG boundary plan must be included in the outline biodiversity gain plan submitted at the application stage. The plan must show the entire order limits with the BNG boundary (the area of the development site of an NSIP that is subject to BNG and must be included in the baseline) overlaid, and must differentiate the following categories:

1. Areas of habitat that will be negatively impacted (both permanent and temporary losses, and where there is a deterioration of habitat condition such as shading caused by the development). This includes habitats that will be returned to their original type and condition after the impact.
2. Areas of habitat that will be used to contribute towards BNG (including any new or enhanced habitats created only for the purposes of BNG or for other purposes such as for EIA and will also be counted for BNG).
3. Unimpacted habitat voluntarily included in the BNG boundary and baseline (retained habitat).
4. Unimpacted habitat within the order limits that are excluded from the BNG boundary and baseline.

“Unimpacted habitat within the order limits that are excluded from the BNG boundary and baseline” (category 4 above)

This category covers the HDD scenario where the land needs to be included within the order limits but the habitat will remain unimpacted (as confirmed by an ecologist). Equally, habitats beneath overhead electricity lines that remain unimpacted can also be excluded. 

Defra’s response to its May 2025 consultation on BNG for NSIPs noted that it would provide guidance to support applicants and their ecologists to determine when on the ground habitat can be considered unimpacted. So far, the relevant guidance appears to be “What to include in biodiversity net gain baselines for NSIPs” (2 June 2026). This guidance is relatively high-level and does not prescribe a detailed evidential standard for determining when habitat can be treated as unimpacted. Accordingly, the robustness of ecologist reasoning and supporting evidence will be important to ensure exclusions from the BNG boundary and baseline withstand scrutiny at examination. The outline biodiversity gain plan must include, among other matters, a brief statement outlining the role and input of qualified ecological professionals in preparing the biodiversity gain plan, including the biodiversity metric calculation and habitat management and monitoring plan. This is a good opportunity for applicants to demonstrate the qualifications and credentials of their ecologists in this regard.

Any habitats that will be impacted, including during site preparation, drilling access points, and temporary storage areas, must be included in the plan. 

Where limits of deviation are used, the realistic worst-case parameters should be applied, not an unnecessarily conservative scenario. Habitats outside that worst-case extent may be excluded from the BNG boundary (and baseline).

Retained habitat – unimpacted habitat voluntarily included in the BNG boundary and baseline (category 3 above)

Applicants should carefully consider the habitat included as “retained habitat”. The guidance notes that an applicant might choose to include unimpacted habitats in the baseline calculation to simplify matters. It notes that applicants should consider including small parcels of unimpacted habitats in the baseline calculation to make the baseline "more proportionate, easier to interpret, and simpler to evidence." Our advice is to consider including habitats under this category very carefully, because any unimpacted habitats included in the baseline calculation will become subject to the 10% BNG requirement. However, on the flip side, such habitats can be included in the post-development biodiversity value and therefore count towards BNG.

What if a biodiversity gain plan is updated or phased?

If a biodiversity gain plan is updated or phased, the baseline must also be revised where there are changes to habitats, development impacts, or site design, and may be updated if impacts are reduced. A completed biodiversity metric tool must be submitted as part of any updated plan submitted after consent is granted. Any updates must be supported with clear evidence, justification, and (where relevant) revised boundary plans, with version control used to track changes.

How must on-site BNG be legally secured?

On-site habitat creation or enhancement being used to contribute towards BNG for NSIPs need to be secured by either a legal agreement (section 106 planning obligation or conservation covenant) or a requirement in the DCO. The legal agreement or DCO requirement must last for at least 30 years from the date the habitat enhancement works are finished. Guidance on legal agreements can be found here.

What is a Habitat Management and Monitoring Plan?

An HMMP can be used alongside or within the legal agreement to provide BNG to provide more information about how habitat will be created, maintained and monitored. For NSIPs, a draft HMMP needs to be submitted with the outline biodiversity gain plan at DCO application stage and an updated HMMP will need to be submitted with any later biodiversity gain plan submissions if the significant on-site enhancements change.

For NSIP developers, this means that ecological survey work, habitat design, and management planning must be sufficiently advanced at the point of application to support a credible draft HMMP. This should be factored into pre-application programmes now.

Guidance on creating an HMMP for BNG can be found here.

How are off-site biodiversity gains allocated?

The standard online service for recording the allocation of registered off-site biodiversity gains on the biodiversity gain site register (here) is not available for NSIP developers. NSIP developers must instead request a paper application form by emailing [email protected]. Developers intending to rely on off-site gains must build these lead times into their project programmes and cannot assume the process will be as straightforward as for developments under the Town and Country Planning Act 1990.

Can developers monetise excess on-site biodiversity gains?

Where an NSIP delivers on-site biodiversity gains exceeding the 10% requirement, those excess gains may be legally secured, registered on the biodiversity gain sites register, and allocated as off-site gains for another development. Applicants must confirm in their outline biodiversity gain plan whether any excess gains will be attributed to their own development or made available for allocation to others. This creates a commercial opportunity for large-footprint NSIP developers, particularly those in the energy, water, and national networks sectors, who may be able to generate surplus biodiversity units and make them available on the off-site market. This also provides an opportunity for portfolio developers with significant landholding available for habitat creation to register surplus units from one project on the biodiversity gain site register and then allocate those to meet the BNG requirement on a separate project within the same portfolio. This effectively enables inter-project BNG offsetting (and potentially avoids the need to purchase statutory biodiversity credits) provided the gains are appropriately recorded on the register and in the biodiversity gain plans. 

What are the pros and cons of submitting DCO applications before the 2 November cut-off?

Where a DCO application is made on or after 2 November 2026, the Secretary of State may not grant development consent unless they are satisfied that the 10% BNG objective in the relevant biodiversity gain statement is met. Applications submitted before this date will avoid the mandatory 10% BNG requirement, although they may include voluntary BNG commitments. Developers with applications that are sufficiently advanced may therefore be considering whether to submit before 2 November 2026 to avoid the BNG obligation entirely. There are arguments in both directions.

The advantages of submitting before 2 November 2026 include that there will be no statutory BNG requirement, which will eliminate the need for an outline biodiversity gain plan, a draft HMMP, a BNG boundary plan and all the associated documentation. This offers a potentially material saving in time and cost at the application stage. It also removes the risk of statutory biodiversity credits being required at significant cost if on-site and off-site gain opportunities prove insufficient.

However, submitting an application that is not examination-ready, principally to beat the BNG deadline, is likely to face sustained challenge during examination, potentially resulting in significant delays that outweigh any BNG-related cost saving. Examining Authorities may, in any event, expect voluntary BNG commitments or equivalent ecological undertakings given the policy context and the prominence of nature recovery in current NPS frameworks. And most NPS documents require applicants to demonstrate net benefit to biodiversity, meaning the substantive ecological work may be necessary regardless of whether the statutory regime applies.

Conclusion

The package of statements and guidance published on 2 June 2026 represents the most significant single addition to the NSIP BNG framework since the Environment Act 2021, delivering all ten biodiversity gain statements and the detailed operational guidance that practitioners have been awaiting. For developers with NSIP projects at any stage – from emerging project scoping through to imminent application – the package contains material new obligations and clarifications that should be reviewed immediately. The window between now and 2 November 2026 is the critical period in which to integrate BNG strategy into project design, pre-application engagement, and programme planning.

If you would like to discuss how this affects projects in your pipeline, please contact us using the details below.