IN Brief:
- England’s mandatory biodiversity net gain rules now apply to qualifying nationally significant infrastructure project applications.
- Applications for development consent orders from 2 November 2026 need an outline plan and statutory biodiversity metric calculation.
- On-site and registered off-site habitat gains can be combined; statutory credits remain a last resort.
Defra has brought mandatory biodiversity net gain into the consenting process for nationally significant infrastructure projects in England. Developers making a qualifying development consent order application on or after 2 November 2026 must demonstrate how their proposals will achieve an increase of at least 10% in biodiversity value. The requirement extends an established principle of English planning law into the regime used for major infrastructure, with separate procedures and documentation.
Schedule 2A to the Planning Act 2008, inserted by the Environment Act 2021, provides the statutory framework. It applies to qualifying nationally significant infrastructure projects seeking a development consent order from 2 November 2026, with the application date establishing whether the new duty applies. Infrastructure authorised through other routes, including hybrid Bills, is treated separately under the legislation.
A major road, railway, energy, or other qualifying development may include permanent works, associated infrastructure, and temporary construction areas spread across several locations. Applicants have to identify the relevant habitats within the biodiversity net gain boundary and calculate their baseline and projected values. Ecology surveys and consistent land boundaries are therefore part of assembling the consent evidence alongside the engineering and environmental assessments.
The statutory biodiversity metric measures habitat value using characteristics including area or length, habitat type, condition, and strategic significance. The required 10% increase concerns biodiversity units, not a fixed proportion of landscaping or trees. Developers must compare the baseline habitat value with the post-development value, accounting for habitat losses, proposed enhancement, and the metric’s adjustments for delivery risk and timescale.
Applications submitted from the commencement date must include an outline biodiversity gain plan describing the strategy for achieving the statutory objective. Applicants must also propose requirements in the draft development consent order that secure delivery. The Secretary of State must be satisfied that the relevant biodiversity gain objective can be met before granting consent, with the applicable biodiversity gain statement forming part of the assessment framework.
Sector-specific biodiversity gain statements cover national networks, energy, airports, water resources, data centres, and other forms of nationally significant infrastructure. Published in June 2026, they carry the same effect as provisions in the relevant national policy statements. Applicants need to apply the statement governing their project type when defining the metric calculation, delivery approach, and supporting documentation.
Habitat creation and enhancement within the project boundary can contribute towards the gain requirement. For nationally significant infrastructure projects, on-site habitat improvements counted as gains must be secured and maintained for at least 30 years from completion of the enhancement works, through a development consent order requirement, planning obligation, or conservation covenant as applicable. That commitment links ecological design with long-term access, monitoring, and land management arrangements.
Where the required gain cannot all be achieved within the project boundary, developers may use registered off-site biodiversity units. The land must be secured for the necessary management period, with the gains recorded and allocated to the scheme. The statutory metric also takes account of the distance between the affected site and off-site habitat, meaning the location of compensating land influences the number of units required.
Statutory biodiversity credits are available as a final route if suitable on-site and registered off-site gains cannot meet the objective. Applicants must explain why those alternatives are insufficient before relying on credits. The metric calculation sits alongside existing environmental obligations: the developer must still avoid and reduce ecological harm where possible and address other protected sites, habitats, and species through the relevant assessment procedures.
Linear infrastructure creates particular challenges because the route can pass through several habitat types and administrative areas, with embankments, drainage, access tracks, and construction compounds affecting the overall boundary. Temporary land take and proposed reinstatement need consistent treatment in the metric. Survey information, construction phasing, and the intended condition of habitats after works are completed will all influence the biodiversity gain plan.
For projects extending beyond England, the mandatory gain calculation concerns habitats within England, with biodiversity measures elsewhere considered separately. Coastal projects are covered as far as the mean low-water mark, including the intertidal zone, while the marine environment beyond it falls outside this statutory calculation. These boundaries require particular attention where a development includes linked terrestrial and marine works.
The new commencement date changes the information required from project teams preparing consent applications. Baseline surveys, metric calculations, an outline gain plan, and enforceable long-term habitat commitments will need to be developed alongside the engineering design. The first applications made under the new regime will test how the statutory requirements are applied to large sites and infrastructure corridors.
