Biodiversity net gain (BNG) becomes mandatory for nationally significant infrastructure projects (NSIPs) from 2 November 2026. From that date, any application for a development consent order (DCO) must deliver at least a 10% measurable improvement in biodiversity — the same headline figure as the town-and-country planning regime, but delivered through a distinct legal machinery of biodiversity gain statements and post-consent gain plans. This post explains what changes, what Defra's ten gain statements require, and what promoters and landowners should be doing now.
The extension completes the rollout begun by the Environment Act 2021: mandatory BNG reached major development in February 2024, small sites in April 2024, and infrastructure is the final piece. Defra confirmed the November date and published the supporting guidance and statements in June 2026.
What changes on 2 November 2026?
- Who it catches: DCO applications made on or after 2 November 2026. Applications submitted before that date are outside the statutory requirement, even if they are examined and decided afterwards — a cliff-edge that is already shaping submission timetables.
- The requirement: at least 10% net gain in biodiversity, measured with the statutory biodiversity metric, across all NSIP types — energy, transport, water, waste and wastewater. There are no sector exemptions and no voluntary opt-in phase.
- The mechanism: instead of the planning-condition route used for ordinary applications, each sector has a biodiversity gain statement setting out how BNG applies; the promoter then submits a biodiversity gain plan for approval after consent, before development begins.
- Duration: habitat enhancements must be secured and maintained for at least 30 years, mirroring the TCPA regime.
The ten biodiversity gain statements
On 4 June 2026 Defra laid ten biodiversity gain statements covering the NSIP sectors — including energy, transport, water resources, wastewater and hazardous waste — plus a statement for development where no national policy statement has effect. From 2 November they take effect as if written into the relevant national policy statement, which means the Examining Authority and the Secretary of State must decide applications against them. Alongside the statements, guidance on preparing BNG baselines for NSIPs explains the evidence expected at application stage: a metric-based baseline, the projected habitat losses and gains, and how the 10% will be achieved and secured.
How NSIP BNG differs from the ordinary planning regime
If you know BNG from housing schemes, the infrastructure version rhymes but does not repeat:
- No small-site relief. The TCPA regime's exemptions — including the new 0.2 hectare exemption arriving on 6 August 2026 (see our guide to the 0.2 ha exemption) — have no NSIP equivalent. Linear infrastructure crossing dozens of habitat parcels is squarely in scope.
- Statement-led, not condition-led. The gain statements define how the requirement bites per sector; the biodiversity gain plan is approved post-consent rather than discharged as a planning condition.
- Same delivery hierarchy. On-site enhancement first, then registered off-site units, with statutory credits strictly the last resort — at the government's deliberately punitive prices (see the 2026 statutory credit price table).
- Irreplaceable habitats — ancient woodland, blanket bog and the rest — sit outside the metric arithmetic and still require bespoke compensation agreed case by case.
What DCO promoters should do now
- Fix your submission date honestly. If the DCO will be made after 2 November, design surveys and land negotiations around a 10% commitment from day one; retrofitting BNG into a mature scheme design is the expensive route.
- Baseline early. Habitat condition surveys are seasonal; a missed summer window can cost a year. The baseline guidance expects metric calculations grounded in current survey data.
- Secure land for delivery. On-site gains along linear schemes are often thin; promoters will compete for registered off-site units in the same national market as housing developers — engaging habitat bank operators early is now a programme-critical task.
- Plan the 30-year governance. Management, monitoring and funding for three decades must be legally secured — through the DCO itself, side agreements or conservation covenants.
What it means beyond the mega-projects
Most applicants will never promote an NSIP, but the change still matters. It completes a policy direction: every tier of development in England now internalises its biodiversity cost, from a self-build plot to a reservoir. Councils increasingly read that direction into what they expect from sustainability statements — clear BNG arithmetic, a credible delivery route and honest treatment of exemptions. And infrastructure demand entering the off-site unit market will influence unit prices for everyone else. For the wider 2026 rule changes affecting ordinary applications, see our summary of the BNG changes and new exemptions.
Key takeaways
- BNG is mandatory for DCO applications made on or after 2 November 2026 — 10%, all sectors, no exemptions.
- Ten biodiversity gain statements take effect as national policy; a post-consent biodiversity gain plan secures delivery.
- The TCPA regime's small-site and 0.2 ha exemptions do not apply to NSIPs.
- Promoters should baseline, secure land and plan 30-year management now; everyone else should expect knock-on demand in the off-site unit market.
How Fortress Associates can help
For the planning applications most of our clients make — new homes, extensions, commercial and mixed-use schemes — our sustainability statement service produces a planning-ready statement covering 10% biodiversity net gain under the Environment Act 2021, water efficiency to the 110 litres per person per day standard, urban greening and BREEAM where required, with the Urban Greening Factor addressed for London sites. The report is free, ready in minutes, and covers every UK local authority. Start with our guide to what a sustainability statement is, or contact us about your project.
Sources & further reading
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