Biodiversity net gain requirements extended from November 2026

A new duty to deliver a minimum 10% net gain in biodiversity will attach to applications for development consent submitted for ‘nationally significant infrastructure projects’ (NSIPs) on or after 2 November 2026. The government confirmed the date for implementing the policy in its response to a consultation it held on the proposals last year.

Imogen Dewar and Fiona Ross of Pinsent Masons, who specialise in major infrastructure consenting and environmental law, said that in addition to the ‘go-live’ date of November now being confirmed, the government response to the consultation provided further detail on various key aspects of the BNG regime.

BNG requirements were enacted in the Environment Act in 2021. In 2024, a duty to deliver a minimum 10% net gain in biodiversity was introduced for planning applications subject to the Town and Country Planning Act 1990 (TCPA). TCPA projects are smaller scale developments that do not meet the statutory thresholds for treatment as an NSIP.

NSIPs are subject to a separate consenting process introduced under the Planning Act 2008 where the decision-making powers rest with the secretary of state, not local planning authorities as with TCPA projects. NSIPs must be granted a development consent order (DCO) to proceed to construction.

Dewar said: “The confirmation that mandatory biodiversity net gain will apply to NSIPs from November 2026 gives important certainty for developers, which can now plan for BNG with greater confidence. However there many key aspects of the BNG regime that still require clarification. The government has committed to releasing guidance, secondary legislation and key policy documents – ‘Biodiversity Gain Statements’ – soon. All of these further documents will need to be scrutinised once available.”

Ross said: “Although the 10% gain objective mirrors the TCPA regime, the way BNG will operate for NSIPs is distinct. Promoters should now be stress‑testing schemes against the forthcoming regime, ensuring strategies and programme assumptions can accommodate the biodiversity requirements well ahead of submission.”

Details of how the BNG for NSIPs regime will operate confirmed in the government’s response include that the BNG objective will be set at 10% gain compared to the pre-development baseline. The territorial scope of the regime was also confirmed – the BNG for NSIPs regime will apply to onshore projects onshore down to the “mean low-water mark”. The government has promised to provide more information “in due course” about the possibility of applying requirements around ‘marine net gain’ to NSIPs.

Alongside the new secondary legislation and guidance, the government has also committed to introducing an updated BNG metric user guide. This will reflect changes to the metric used for TCPA schemes to accommodate a NSIP-specific metric.

There will be no sector-specific exemptions for different classes of BNG development.

The government has confirmed that unimpacted habitats within a DCO’s site boundary (the ‘Order Limits’) do not need to be included in the BNG baseline. The 10% BNG requirement instead applies to a smaller area, where land is disturbed by the project, referred to as the BNG boundary. The BNG boundary includes habitats within the DCO’s Order Limits that are disturbed, both temporarily and permanently.

In relation to temporarily disturbed land, the existing temporary habitats provisions – by which land that is disturbed then restored within two years is not treated as lost within the BNG metric – will be extended to NSIP proposals. The government is also looking into extending the ‘two-year rule’ to a five-year period. Further guidance and details on this are anticipated.

Application and examination phase

Under the new policy, BNG considerations will need to be factored in at all stages of a project lifecycle. In the conception and promotion phase, developers will need to “avoid or minimise habitat loss by considering biodiversity in site selection and site design”. During the pre-application phase, they will need to use a statutory biodiversity metric to calculate indicative biodiversity values both for pre- and post-development. An ‘outline biodiversity gain plan’ (ODGP) will need to be drawn up and draft requirements on BNG proposed for the DCO application.

The ODGP and draft BNG requirements must be submitted as part of the DCO application. The examining authority appointed to hear the application will determine whether the BNG objective has been met, and will set out their position when recommending to the secretary of state whether they should grant consent for the project.

Where consent is granted, developers will have to obtain approval for an updated biodiversity gain plan before they can proceed with development. The development will be subject to ongoing management, monitoring, reporting and appropriate enforcement of BNG during the lifetime of the project.

BNG delivery

The government’s consultation response confirms that BNG measures can be applied on-site or off-site in the first instance. As a last resort, developers can purchase biodiversity credits from the government’s statutory credit market.

The policy also addresses the concept of ‘irreplaceable habitat’, which the government has defined as “those which would be technically very difficult (or take a very significant time) to restore, recreate or replace once destroyed”. A list of irreplaceable habitats is set out in existing regulations. Developers will be expected to record irreplaceable habitats relevant to their development plans, but the biodiversity value of the irreplaceable habitats will not be included in the baseline and the 10% BNG obligation will not apply. Developers will still need to be prepared to compensate for losses or deterioration to irreplaceable habitat on-site, though they will not be able to do so through the purchase of biodiversity credits and such compensation cannot count towards satisfying their BNG obligation. However, where their plans will enhance irreplaceable habitats those habitats will be included in the BNG baseline and the 10% BNG obligation will apply.

While the government has confirmed that developers intending to deliver off-site biodiversity gains rather than on-site will in most cases not be subject to a spatial risk multiplier penalty when doing so within any of the local authority areas or national character areas that the NSIP is located in, this safe harbour will not apply to watercourse units where a project spans multiple catchment areas.

Securing BNG

Under the finalised policy, all onsite habitat creation and enhancement counted towards the post-development biodiversity value is to be considered significant and therefore must be secured. The reinstatement of existing habitats – where temporary loss of habitat is replaced with the same type in same condition as what was before – will be considered non-significant and does not need to be secured.

Ross said: “The introduction of a more narrowly defined BNG boundary and the treatment of temporary land ensures a proportionate position, ensuring that major infrastructure projects contribute to nature restoration whilst reflecting the impacts that they have, particularly for projects that involve significant underground works and/or temporary land. In addition, the confirmation that spatial risk multipliers will not apply to off‑site NSIP gains within wider administrative areas but will still apply to watercourse units spanning multiple catchments, is likely to be an important issue for large-scale projects interacting with the water environment.”

Biodiversity gain statements (BGS), applicable to different types of infrastructure, will now be developed to inform NSIP applications and consenting decisions. The government said that, in May, it will lay BGSs for all NSIP types before parliament. Those statements “will have the same effect” as if they were in the national policy statements (NPSs) – the documents that govern how applications for NSIPs should be assessed – once BNG is live, and “will later be incorporated into the relevant NPS when they are next reviewed”, it said.