Infrastructure Planning Blog

This week's entry focuses on the full guidance document as to how to deal with biodiversity net gain (BNG) when applying for a nationally significant infrastructure project (NSIP), which was published on 26 August.

The mandatory obligation to replace any lost habitat with at least 10% more new habitat will apply to all NSIP applications made from 2 November 2026, less than two months away now.  The same exemptions apply as to town and country planning applications but almost every NSIP will be above the thresholds. Not every one, perhaps, e.g. if a capacity cap was being lifted without any development occurring then that might be exempt yet still amount to an NSIP.

Anyway, the new guidance document can be found here, and it's a whopper - if printed, it would be 11 pages long.

If you have been following the announcements about how BNG will apply to NSIPs and what this blog has said about it (e.g. blog 46 here and blog 53 here), the bits that I think are new are:

• if you are planning to include land already allocated to development for BNG, it recommends negotiation, but concedes that 'you may need to amend, compensate for or take on the legal agreements that are already in place'; the message is really to avoid such sites where possible - taking on the obligations is an interesting option;
• you are advised to engage with local authorities and the Planning Inspectorate on your choice of biodiversity gain plan (BGP) discharging body or bodies given it could be all LPAs, one LPA or the Secretary of State;
• there are some helpful scenarios about uncertainty of location of impact;
• the guidance deals with bird strike issues from creating habitat near aerodromes; and
• it covers what you might do if you are exceeding a 10% gain onsite, i.e. still allocate the onsite gains to the current development, sell them to somebody else on the offsite market, use them for your other projects elsewhere, or a combination.

If you understand BNG for town and country planning, the similarities are:

• the same 10% gain obligation is imposed;
• the same three metrics are used (area, hedgerow and watercourse);
• the same register of offsite sites is used;
• a BGP must be approved before construction can start (but is only the middle of three stages in the case of NSIPs, see below);
• ecologists are needed to determine habitat type and condition;
• low and very low distinctiveness habitats count as retained if fully restored within five years of damage, for higher distinctivenesses it's two years; they are still included in the BNG boundary but only 10% gain is needed; and
• baseline data should be at the application date.

And the main differences are:

• guidance is effectively contained in this newly-released document plus 'biodiversity gain statements' for each type of infrastructure (with identical contents), which have NPS status; other BNG guidance has been updated to mention NSIPs;
• not all land within the order limits need be included in baseline calculations, unaffected land, usually because you're going below or above it, can be outside a 'BNG Boundary', and a 'realistic worst case' can be used for narrower corridors within order limits where their maximum width is known;
• you may not be able to survey all order land due to access issues; use the highest value habitats likely to be present;
• instead of just a pre-commencement BGP that needs approval, you need an outline one with your application (the contents of which are covered by the guidance), an updated one before you can commence, and you can even leave some details to be finalised before operation;
• like small developments, there is no preference between onsite and offsite BNG but there is still a spatial penalty for further away habitat (or is there? See below);
• land subject to temporary possession does not need to be secured for BNG (i.e. it can be included in the calculations but does not need to be legally secured for 30 years, as it will not be considered 'significant' onsite gain) as long as there is a commitment to restore it to its original condition;
• the BGP discharging authority can be each LPA for its area, one LPA for the whole lot or the relevant Secretary of State; and
• up to four requirements should be included in your application version of a draft development consent order (DCO) to deal with BNG, which along with the outline BGP are the main changes to applications.

Further points to note

This is all very complicated and you clearly need specialist advice from someone who has been involved in both the NSIP and BNG regimes from the start to navigate successfully. My details are below...

Some particular thoughts:

• the most important message is to consider BNG at the very start of a project as it can influence design and siting – and cost;
• the guidance probably shouldn't say the habitats that 'will' be negatively impacted by the development as one of the main features of NSIPs is that much land is included that only may be built upon, but which land won't be decided until post-consent detailed design;
• perhaps it shouldn't refer to very low distinctiveness habitat being impacted either - its score is already zero;
• the guidance doesn't discourage including remote sites in the order limits to avoid spatial multiplier penalties, but securing the land may be an issue and 10% gain would be needed on top;
• using BNG enhancement and creation to deliver other benefits is encouraged - the examples given are 'infrastructure resilience, social benefit, delivery of other environmental obligations and habitat connectivity';
• the guidance still refers to the spatial multiplier in terms of local planning authorities and national character areas rather than local nature recovery strategy areas;
• the guidance says something I think should also be emphasised for town and country planning applications: consider whether the habitat can withstand the expected levels of use where there is public access;
• the guidance has various suggestions for how to find offsite units - if the register had been the marketplace this would not be necessary; and
• DCO change applications are not technically subject to BNG but you are expected to say how the achievement of 10% gains would be affected.

I hope that was a useful rundown, whatever your level of knowledge of BNG. Do get in touch if you have any questions or comments, I'd be interested to hear them. We are intending to host an event at our office on switch-on day, 2 November - watch out for further announcements!

This publication is intended for general guidance and represents our understanding of the relevant law and practice as at September 2026.  For more information see our terms & conditions.