Ten percent is no longer a target on a future horizon. As of today, 2 November 2026, it is a legal minimum. Every Development Consent Order application for a Nationally Significant Infrastructure Project submitted from this date must show at least 10% biodiversity net gain before consent can be granted.
This is not a drill, and it is not a countdown anymore. The rule is live. After slipping past earlier expectations, Defra confirmed the timetable in April 2026, and the clock has now run out. Standard housing and commercial schemes under the Town and Country Planning Act have worked under mandatory BNG since 2024. NSIP promoters, the people behind power lines, reservoirs, railways and energy infrastructure, are now in the same boat, with a bespoke metric built for the scale and complexity of their projects.
At Biodiversity Surveyors, we have spent months preparing clients for this transition. This guide sets out exactly what changes from today and what applicants need to do first.
Key Takeaways
- Biodiversity net gain NSIP 2 November 2026 rules apply to every DCO application submitted on or after today, under the Environment Act 2021 framework.
- An outline biodiversity gain plan (OBGP) must accompany the DCO application; a full, updated plan needs approval before works begin.
- The BNG boundary is wider than the red line, it covers all land temporarily or permanently disturbed, including compounds, access routes and laydown areas.
- Irreplaceable habitats such as ancient woodland and veteran trees sit outside the baseline and the 10% target, and cannot be offset with statutory credits.
- Barclays analysis reported on 15 October 2026 warns that NSIP demand could squeeze the supply of off-site biodiversity units, making early procurement a priority.
What Changes Under Biodiversity Net Gain NSIP 2 November 2026 Rules
The core obligation is simple to state: at least 10% net gain in biodiversity value, measured against a baseline, using a metric designed specifically for NSIPs rather than the standard planning metric.
Two documents now sit at the heart of every DCO submission.
The outline biodiversity gain plan (OBGP) must accompany the application itself. It sets out the intended approach, baseline, boundary, likely gains, and how losses will be addressed.
The full, updated biodiversity gain plan follows later and must be approved before any works start on site. This is where the detail, contracts and legal agreements need to be locked down.
Only habitats that are negatively affected by the project enter the baseline calculation. Habitats left untouched do not count towards the loss side of the ledger, which keeps the assessment focused on genuine impact.
Why the Boundary Matters More Than the Red Line
A common mistake in early NSIP BNG planning is assuming the biodiversity boundary matches the application's red-line boundary. It does not.
The BNG boundary captures all land temporarily or permanently disturbed, including:
- Construction compounds
- Access roads and haul routes
- Laydown and storage areas
- Any land affected by construction activity, even briefly
If a habitat is disturbed and restored within two years, it is currently not treated as a loss, though government is considering extending that window to five years. Applicants should plan surveys and restoration methodologies with that possible change in mind, rather than assuming the two-year rule will last the life of their project.
Practical Checklist for DCO Applicants From Day One
Promoters moving through pre-application or early DCO stages now need to build BNG into the programme, not bolt it on afterwards.
1. Commission Baseline Surveys Early
The baseline survey drives everything downstream, the metric calculation, the OBGP, and the eventual gain plan. Delayed surveys mean delayed applications. Seasonal survey windows for certain habitats make early instruction essential.
2. Map the BNG Boundary Separately From the Red Line
Treat the biodiversity boundary as its own exercise. Walk through every compound, access route and laydown area with the ecology team before finalising the application boundary, so nothing is missed.
3. Identify and Ring-Fence Irreplaceable Habitats
Ancient woodland and veteran trees are excluded from the baseline and the 10% target entirely. They cannot be compensated using statutory biodiversity credits. Where these habitats fall within or near the project footprint, route design around them wherever feasible and document the exclusion clearly in the OBGP.
4. Understand the Catchment Rule for Water Habitats
Off-site gains can generally be delivered in any affected local planning authority area. Water-related impacts, however, must be compensated within the same catchment. This geographic constraint can narrow the available options sharply for linear infrastructure crossing multiple catchments.
5. Start Procuring Units Now, Not Later
Barclays analysis reported on 15 October 2026 flagged a real risk: rising NSIP demand for off-site biodiversity units could tighten supply across the market. Promoters who wait until the full gain plan stage to shop for units risk finding the best sites already allocated elsewhere.
6. Remember the Scope Is Onshore Only
The regime extends to the mean low-water mark and no further. Offshore elements of a project sit outside the BNG requirement, which matters for energy and marine-linked infrastructure with mixed onshore and offshore components.
7. Plan for 30 Years of Monitoring
Habitat monitoring and management commitments typically run for 30 years. This is a long-term liability that needs to be reflected in land agreements, funding mechanisms and ongoing management contracts from the outset, not treated as an afterthought once consent is granted.
How This Sits Within the Wider 2026 BNG Landscape
NSIPs are not the only part of the system shifting this year. Several other changes affect the broader market that NSIP promoters now compete within for units and expertise.
| Change | Effective | Detail |
|---|---|---|
| Small site exemption | From 31 July 2026 | Sites of 0.2 hectares or below exempt from mandatory BNG |
| Self/custom-build exemption | Removed | No longer exempt from BNG requirements |
| Brownfield consultation | Closed 10 June 2026 | Proposed exempting brownfield residential sites up to 2.5 hectares; outcome not yet confirmed |
Separately, the Office for Budget Responsibility's October 2026 forecast, published alongside the 28 October Budget, cut projected UK net housing additions by 190,000, citing BNG among the regulatory costs weighing on housebuilding. That figure is a reminder that biodiversity obligations are now a genuine line item in national housing delivery forecasts, not a niche planning condition.
For NSIP promoters, the practical read-across is competition. If unit supply tightens across residential and infrastructure sectors simultaneously, early procurement becomes even more valuable.
Conclusion
From today, biodiversity net gain NSIP 2 November 2026 requirements are a fixed part of the DCO process, not an emerging risk to monitor. Applicants submitting now need baseline surveys, a properly mapped BNG boundary, a realistic OBGP and an early procurement strategy for off-site units.
Biodiversity Surveyors works with promoters and their consultants to run NSIP-specific baseline assessments, calculate the bespoke metric, and build defensible outline and full gain plans. Contact the team early in your pre-application timeline, before the survey season closes and before the best off-site units are gone.
FAQ
Does biodiversity net gain NSIP 2 November 2026 apply to applications already submitted before this date?
No. The 10% requirement applies to DCO applications submitted on or after 2 November 2026, following the timetable Defra confirmed in April 2026.
Can ancient woodland losses be offset with biodiversity credits?
No. Ancient woodland and veteran trees are irreplaceable habitats, excluded from the baseline and the 10% target, and cannot be compensated using statutory biodiversity credits.
What is the difference between the OBGP and the full biodiversity gain plan?
The outline biodiversity gain plan (OBGP) accompanies the DCO application. The full, updated plan must be approved before construction works begin.
Do offshore works need to meet the BNG target?
No. The regime is onshore only, extending to the mean low-water mark.
How long do habitat monitoring commitments last?
Monitoring and management typically run for 30 years under the current framework.
Should professional advice be sought before finalising a DCO application?
Yes. Given the technical complexity of the NSIP metric and catchment rules, professional ecological and planning advice should be taken on a case-by-case basis.