Mandatory Biodiversity Net Gain has taken effect for Nationally Significant Infrastructure Projects in England, requiring Development Consent Order applications made on or after 2 November 2026 to deliver at least a 10% increase in biodiversity value.
The Planning Inspectorate updated its NSIP application guidance on 2 November to reflect the change. Covered applications must now include an outline biodiversity gain plan showing how the 10% objective will be met, while the draft DCO must contain requirements securing delivery of that objective.
Illustrative view of habitat creation alongside a major infrastructure construction corridor, showing the relationship between temporary works, ecological assessment and biodiversity gain delivery. Photo: London Construction Magazine
The trigger is the DCO application date
The statutory framework comes from section 99 and Schedule 15 of the Environment Act 2021, which amended the Planning Act 2008 and inserted Schedule 2A. The Environment Act 2021 (Commencement No. 11) Regulations 2026 brought those provisions into force on 7 May 2026.
The operative date for applications is set through the biodiversity gain statements published by Defra. The sector biodiversity gain statements apply the objective to relevant DCO applications made on or after 2 November 2026 and have the same effect as if they were included in the relevant National Policy Statement.
This means the key transition point is submission of the DCO application. A project that carried out design, consultation or environmental work before 2 November does not escape the regime if its DCO application is made on or after that date.
The requirement applies to NSIPs, or parts of NSIPs, in England as far as the mean low-water mark, including the intertidal zone. For cross-border projects, the mandatory baseline, metric and biodiversity gains apply to the English component. Infrastructure consented through routes such as Hybrid Bills sits outside this NSIP BNG framework.
BNG now sits inside the DCO application
The Planning Inspectorate's application guidance requires the outline biodiversity gain plan to set out how the development will achieve at least 10% BNG. Applicants must also propose DCO requirements that secure the biodiversity gain objective.
Defra's NSIP BNG guidance requires a single statutory biodiversity metric calculation for the development and a BNG boundary plan. The boundary plan must distinguish habitats that will be lost or deteriorated, areas proposed for biodiversity gains and unimpacted habitats that are included or excluded from the baseline.
The BNG boundary is therefore not automatically the same as the full DCO order limits. The baseline includes habitats inside the order limits that will be negatively affected by the development, either permanently or temporarily, together with areas that will be used to deliver on-site gains.
That brings construction compounds, storage areas, access routes and other temporary construction land into the calculation where they cause habitat loss or deterioration. Where a temporarily affected habitat is reinstated to the same habitat type and condition, Defra treats that reinstatement as non-significant for securing purposes. Habitat creation or enhancement being counted as a significant gain must be legally secured.
LCM has previously examined why physical ecological measures do not by themselves prove compliance in its guide to wildlife crossings and green bridges. Under the NSIP regime, the statutory metric, gain plan and legal securing mechanism determine whether the 10% objective is met.
Habitat obligations extend beyond construction
All on-site habitat creation or enhancement used as a significant biodiversity gain must be maintained for at least 30 years from completion of the habitat works. Defra allows those gains to be secured through DCO requirements, section 106 obligations or conservation covenants.
Where on-site gains are proposed, the application documentation must include a habitat management and monitoring plan. Updated gain plans and associated documents then move into the post-consent process, with the relevant discharging authority responsible for approving the updated biodiversity gain plan before development covered by the requirement can commence.
For long construction programmes, this moves ecology beyond a consent-stage assessment. Baseline assumptions, temporary construction footprints, habitat reinstatement and long-term management commitments can all affect design development and the programme for discharging DCO requirements.
The issue is particularly relevant to linear infrastructure, where compounds, access routes, working widths and temporary land can cover a substantial area. LCM's earlier examination of the A417 wildlife bridge and long-term ecological performance showed how infrastructure delivery can continue to carry habitat management and monitoring obligations long after the structural work itself is finished.
Statutory credits can become expensive quickly
NSIP promoters can develop on-site and off-site BNG options in parallel. Registered off-site biodiversity units can be allocated to the development, while statutory biodiversity credits remain the last-resort route where sufficient on-site and off-site gains cannot be secured.
Defra requires two statutory biodiversity credits for every one biodiversity unit needed to close a shortfall. LCM calculated the effective cost per missing unit from the statutory biodiversity credit price list in force on 2 November 2026.
| Credit category | Defra price per credit | LCM cost per missing unit |
|---|---|---|
| A1 | £42,000 | £84,000 |
| A2 | £48,000 | £96,000 |
| A3 | £66,000 | £132,000 |
| A4 | £125,000 | £250,000 |
| A5 high-distinctiveness lakes | £650,000 | £1.3m |
| Hedgerow | £44,000 | £88,000 |
| Watercourse | £230,000 | £460,000 |
Those figures are last-resort statutory credit costs, not estimates of the BNG bill for a particular infrastructure scheme. The number and type of units required depend on the statutory metric calculation, and Defra states that its published credit prices do not include any applicable spatial risk multiplier.
How LCM calculated this
LCM reviewed Defra's statutory biodiversity credit price list on 2 November 2026. Defra requires developers using statutory credits to buy two credits for every one biodiversity unit needed. LCM multiplied each published credit price by two to show the effective cost of closing a one-unit shortfall before any spatial risk multiplier.
A new consent and programme constraint
The new regime makes biodiversity evidence part of the DCO application itself. Applicants need the ecological baseline, statutory metric, BNG boundary and delivery strategy sufficiently developed when the application is submitted, rather than leaving the biodiversity calculation entirely to the post-consent stage.
The Planning Inspectorate's updated 2 November guidance also requires the completed biodiversity metric calculation tool to be submitted in its original Excel format so that the information can be reviewed. Where on-site gains are proposed, the supporting application package includes the habitat management and monitoring material required by the relevant biodiversity gain statement.
For contractors and promoters, the immediate construction issue is the relationship between the ecological baseline and the land actually needed to build the scheme. Compounds, haul routes, storage areas and maximum working widths can affect the biodiversity calculation where they disturb habitat, while significant gains create management and monitoring duties lasting at least 30 years.
Any NSIP promoter making a DCO application from 2 November 2026 therefore enters examination with the 10% biodiversity objective already embedded in its application documents and draft consent requirements. The Planning Inspectorate's guidance was formally updated on 2 November 2026 to reflect that position.
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