BNG for NSIPs: DEFRA guidance and biodiversity gain statements

DEFRA has published new guidance and sector biodiversity gain statements for nationally significant infrastructure projects (NSIPs), clarifying how mandatory biodiversity net gain (BNG) will operate from 2 November 2026.

The guidance provides greater certainty for NSIP promoters, including clarification on baselines, limits of deviation and the role of sector-specific policy statements as the industry prepares for the introduction of mandatory BNG in England.

The update follows DEFRA’s April 2026 consultation response (Consultation) and brings the main NSIP BNG materials together in a single GOV.UK collection. Much of the guidance builds on the Town and Country Planning Act 1990 (TCPA) regime, but with targeted additions for the scale, complexity and delivery model of NSIPs. For more detail on the Consultation response, please see our article here.

One of the most useful additions is new NSIP-specific guidance on BNG baselines, entitled “What to include in biodiversity net gain baselines for NSIPs”. This confirms that, in some cases, NSIP baselines will need to be approached differently from TCPA schemes — particularly where project design, land take and limits of deviation are still being refined at application stage. We have considered some key elements of the guidance below.

When can habitats be left out of the baseline?

The guidance confirms that unimpacted habitats do not need to be included in the BNG baseline. This is particularly helpful for infrastructure delivered above or below existing habitats. Where, for example, above or below-ground works or construction methods avoid a habitat without disturbing, impacting or degrading it, that habitat can be excluded.

This is a practical and welcome clarification. It recognises that techniques such as horizontal directional drilling or pylon rewiring which do not damage surface habitats should not be required to deliver a BNG uplift.

How should limits of deviation be treated?

NSIPs are often promoted with a degree of flexibility allowed in the design by reference to limits of deviation. The guidance recognises that the BNG baseline should therefore be based on a realistic worst-case scenario, informed by the maximum design and construction parameters, but should not be “overly precautionary”. This is particularly important for linear projects, where the baseline may be based on the maximum construction working width rather than the as-built corridor.

However, the guidance also states that, where there is a reasonable likelihood that works may affect higher-value habitat, the baseline should assume that the habitat will be impacted. An assumption of no impact will only be accepted where measures are in place to secure that outcome, for example through controls in an environmental management plan.

How do the biodiversity gain statements fit in?

A significant part of the update is the publication of 10 biodiversity gain statements, corresponding to the relevant NSIP categories.

These statements will be the policy basis for BNG in the NSIP regime. Under the Planning Act 2008, they set out how development must achieve BNG and are to be treated as forming part of the relevant National Policy Statement (NPS) for an NSIP. The Secretary of State must therefore have regard to the relevant biodiversity gain statement when determining an NSIP application.

DEFRA published a model biodiversity gain statement with the Consultation to give applicants an indication of what to expect. That model has now been adopted, largely unchanged, across the sector-specific biodiversity gain statements.

Biodiversity gain statements have been formally laid in Parliament for the following sectors:

• Airports
• Data centres
• Development where no National Policy Statement has effect
• Energy
• Geological Disposal
• Hazardous Waste
• National Networks
• Ports
• Waste Water
• Water Resources

The final statements follow the same structure and are largely consistent across sectors. The main differences are the links to the relevant NPSs. Where no NPS is in effect, the biodiversity gain statement does not link to an NPS and the relevant sections are instead supported by the National Planning Policy Framework.

Why are data centres are included?

A biodiversity gain statement has also been published for data centres, ahead of the NPS that is currently in preparation. Although data centres are not a defined NSIP category under the Planning Act 2008, the Infrastructure Planning (Business or Commercial Projects) (Amendments) Regulations 2025 came into force in January 2026, enabling data centre developers to seek a section 35 direction so that their project can be considered through the NSIP regime. See our article here, which discusses the Government’s current strategy for data centres in the context of national infrastructure planning.

Is there scope for future divergence?

Although the differences between the biodiversity gain statements are currently limited, the statements create a framework for future sector-specific divergence. That may be particularly relevant in sectors where BNG could have a disproportionate impact, such as linear infrastructure schemes or nuclear development. Notably, there is currently no biodiversity gain statement for nuclear decommissioning. That is significant given the Nuclear Regulatory Review 2025 statement that nuclear decommissioning activities should be excluded from BNG. In its April 2026 response, DEFRA stated that further work was ongoing between DEFRA, DESNZ and the Nuclear Decommissioning Authority to clarify whether further improvements are needed to the BNG regime for those works. It remains to be seen how this will be resolved in policy.

What does this mean for promoters?

The guidance is a welcome step towards a fully functioning NSIP BNG regime. It confirms that promoters will not necessarily need to include every habitat within a project boundary, but they will need clear evidence to justify any exclusions.

For projects with limits of deviation, evolving design parameters or complex land take, early BNG strategy will be important. Promoters should consider how baseline assumptions will be evidenced, secured and explained through the application process.

Contact us

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