The Government has finally published its consultation outcome response for the tailored version of the mandatory Biodiversity Net Gain (BNG) regime to be introduced for Nationally Significant Infrastructure Projects (NSIPs). It is now busy putting both the legislative and policy infrastructure in place to implement this in November this year, one year later than originally intended.
This article considers where the Government has landed with mandatory BNG for NSIPs and considers both the similarities and differences between the form of BNG to be implemented for NSIPs and the form already in place for most town and country planning applications (TCPA) in England.
BNG for NSIPs: A Brief Recap
Mandatory BNG was introduced by the Environment Act 2021 and already requires most planning applications submitted in England pursuant to the Town & Country Planning Act 1990 (the TCPA) to deliver at least a 10% biodiversity net gain. This gain is calculated via a statutory metric tool based on the site’s pre-development biodiversity value. The requirement is met by either providing, in accordance with the BNG hierarchy, one or a combination of onsite BNG, offsite BNG (known as biodiversity units) or statutory credits.
A tailored version of mandatory BNG will now be extended to the DCO regime, applying to all NSIP applications made from 2 November 2026 onwards. This extension has been in prospect for some time, with the Government undertaking its first consultation on applying mandatory BNG to NSIPs in 2022 and publishing its consultation response in February 2023. The intention at that time was that BNG for NSIPs would be implemented in November 2025.
However, following the launch of a further consultation last summer – the key takeaways of which we explored in our previous article – this long-standing target date was quietly deferred to May 2026.
The Government’s recently published consultation outcome response sets the latest implementation date of 2 November for BNG for NSIPs, since which there has been a flurry of related activity, including the publication of new statutory instruments, associated guidance and the biodiversity gain statements for NSIPs.
Mandatory BNG for NSIPs vs Mandatory BNG for TCPA Schemes: What’s the Same?
With the sense that the latest implementation date is one that the Government will be sticking to this time, where has the Government landed with mandatory BNG for NSIPs?
Well, in truth, very little has changed from what was set out in either the 2023 or 2025 consultation papers. This is largely because the Government has maintained the consistent position that, although the legal mechanism for BNG for NSIPs must be tailored to the DCO process, in substance mandatory BNG should be the same as that for TCPA applications.
As such, all of the following aspects are familiar from mandatory BNG for planning applications in England:
- The biodiversity gain objective for NSIPs being at least 10%;
- Use of the statutory biodiversity metric to calculate the requisite BNG;
- Delivery of BNG being onsite, offsite or via the purchase of statutory biodiversity credits;
- BNG being a minimum 30 year commitment; and
- Offsite BNG being registered and allocated to the project in the same way as for TCPA applications.
Mandatory BNG for NSIPs vs Mandatory BNG for TCPA Schemes: What’s Different?
Leaving aside the inevitable process differences between the DCO and TCPA regimes, there are some notable differences of substance. This is notwithstanding the Government’s desire that mandatory BNG should be the same as that for town and country planning applications. In particular:
1) There will be no exemptions
Unlike in the TCPA regime where there are a growing number of exemptions for different development types/circumstances, as we discussed in a previous article, all NSIPs are to be subject to mandatory BNG in the same way. This means that there are no sector specific exemptions and, in particular, linear schemes, projects with intertidal components and net zero infrastructure are all to be subject to mandatory BNG in exactly the same way as other DCO projects.
According to the consultation outcome, this “creates a level playing field and reduces complexity”.
2) Calculation of baseline by reference to the BNG Boundary, not the Order Limits
The new concept of the BNG Boundary is to be introduced for BNG for NSIPs. This is intended to be the area within the Order Limits where habitat will be affected. It will mean that unimpacted habitats within the Order Limits do not have to be included in the baseline calculation.
This is a notable departure from last year’s consultation paper where the Government had stated its clear intention for all land within the DCO Order Limits to be subject to BNG. Although 60% of respondents apparently supported this position, it appears that the Nuclear Regulatory Review 2025’s recommendation for low carbon infrastructure that BNG should only apply to land affected may have influenced the sudden shift in direction here.
3) The Biodiversity Gain Hierarchy is to work differently for NSIPs
Specifically onsite and offsite BNG are to have the same priority, rather than onsite BNG being preferential to offsite BNG.
Whilst part of the rationale for this is to avoid DCO promoters using compulsory purchase powers to acquire land for BNG, this is a significant departure from the mandatory BNG regime that was implemented for TCPA applications (although interestingly the Government is now making the same change for minor development within the TCPA regime albeit for different reasons).
4) Spatial Risk Multiplier
NSIPs will be able to allocate offsite biodiversity gains in any local area that the BNG Boundary is located within without incurring any Spatial Risk Multiplier penalty.
5) Temporary impacts
NSIPs will have 5 year period to restore temporarily impacted habitat of low and very low distinctiveness. This contrasts with the current 2 year period in the TCPA regime.
Concluding Thoughts
Notwithstanding the Government’s desire for mandatory BNG to be the same for all development sectors and types in England, it is inevitable that there will be some substantive adaptations for NSIPs to reflect the differences in the scale and nature of these projects when compared to most TCPA developments.
It also seems likely that, once implemented, mandatory BNG for NSIPs will continue to evolve, as it is presently doing within the TCPA regime. This could mean that, in time, differences emerge for different sectors and types of DCO project, as much as between the NSIP and TCPA regimes generally. Certainly one of the lessons from the TCPA regime are that a “one size fits all” approach to BNG has its own complications – hence the recent changes the subject of our separate article.
One area of overlap between the NSIP and TCPA BNG regimes – and therefore potential “pinch point” – is the offsite biodiversity units market. Whether that market will be able to satisfy the future demand when mandatory BNG for NISPs goes live remains to be seen, although the Government will no doubt hope that it has provided sufficient notice to all stakeholders to prepare.
Whilst the extension of the mandatory BNG regime to NSIPs has been in prospect for some time, it is easy to forget that, as originally set out in the then Environment Bill, mandatory BNG was not intended to apply to NSIPs; it was only included when the Government changed its position in response to widely expressed concerns at the time. Considered in that context, the fact that mandatory BNG for NSIPs is now on the cusp of being implemented – albeit one year later than originally intended – is itself quite a landmark.
If you would like to know more about BNG or otherwise require any planning advice or assistance, please do not hesitate to contact Michael Dempsey or other members of the Planning, Infrastructure & Public Law Team at Broadfield.
