Biodiversity Net Gain for NSIPs: What developers and landowners need to know ahead of November 2026

The statutory basis for BNG for NSIPs is established through amendments made by the Environment Act 2021 to the Planning Act 2008.

In particular:

• Sections 103–105 of the Planning Act 2008 have been amended; and
• A new Schedule 2A has been inserted into the Act.

Under this framework, the Secretary of State must not grant development consent unless satisfied that the application meets the biodiversity gain objective set out in the relevant biodiversity gain statement. In practice, this introduces a new mandatory hurdle within the Development Consent Order (DCO) process.

The government has confirmed that mandatory BNG will apply to NSIP applications submitted on or after 2 November 2026.

This delayed commencement reflects industry feedback on the complexity and scale of NSIPs and is intended to allow sufficient time for:

• scheme design to evolve to incorporate biodiversity enhancements;
• land negotiations to reflect long‑term habitat delivery; and
• supply chains for off‑site units and statutory credits to mature.

Importantly, BNG will not apply retrospectively. Post-consent changes to DCOs will not trigger mandatory BNG where the original DCO application was made before 2 November 2026. This avoids the need to retrospectively calculate and secure biodiversity gains for consented schemes.

All NSIPs will be subject to a biodiversity gain statement, which will play a central role in both the examination of applications and the Secretary of State’s decision‑making.

A biodiversity gain statement will:

• define the biodiversity gain objective (at least 10% net gain);
• set out how biodiversity value must be calculated;
• explain how gains are demonstrated and verified; and
• provide the basis for scrutiny by the Examining Authority and ultimately the Secretary of State.

Developers should expect biodiversity to feature more prominently across the examination process, with clear expectations against which proposals are assessed.

• Defra has committed to publishing biodiversity gain statements for every National Policy Statement (NPS) in May 2026.
• Once mandatory BNG is in force, these statements will have the same effect as if they were included in the relevant NPS.
• The statements will later be formally incorporated when NPSs are next reviewed.
• For NSIPs without an applicable NPS, Defra will publish standalone biodiversity gain statements.

To meet the statutory objective, the biodiversity value attributable to the development must exceed the pre‑development biodiversity value of the on‑site habitat within the “BNG Boundary” by at least 10%. The BNG Boundary includes habitats within the order limits negatively affected (permanently or temporarily) by the development and/or used to contribute to BNG.

That uplift can be delivered through a combination of:

• on‑site habitat creation or enhancement;
• off‑site biodiversity units; and
• statutory biodiversity credits (as a last resort).

As with the Town and Country Planning Act regime, the use of off‑site units and credits is expected to follow a clear mitigation hierarchy, with increasing scrutiny where on‑site delivery is limited.

The biodiversity gain objective:

• applies only to NSIPs, or components of NSIPs, in England;
• applies up to the mean low‑water mark, including the intertidal zone; and
• does not apply to works in the marine environment beyond the intertidal zone.

For cross‑border projects, this means that BNG calculations and delivery will need to be aligned specifically to English components of the scheme.

Applicants will be required to submit an outline biodiversity gain plan as part of their DCO application to the Planning Inspectorate.

The outline plan must set out:

• the applicant’s strategy for achieving at least 10% net gain; and
• how biodiversity gains will be calculated, secured and managed over the long term.

While detailed delivery mechanisms may be finalised post‑consent, this requirement means that BNG will need to be embedded early in project design, land referencing and environmental assessment work.

Between now and November 2026, Defra has committed to:

• laying the necessary secondary legislation;
• publishing biodiversity gain statements for all NSIP types in May 2026;
• issuing an updated biodiversity metric user guide tailored to NSIPs; and
• publishing further guidance to support implementation.

Defra will continue to work with industry stakeholders, the Planning Inspectorate and local planning authorities to support readiness. Post‑implementation, the regime will be monitored and may be refined, including the possibility of future exemptions where justified and supported by evidence.