Biodiversity net gain on major infrastructure projects

Mandatory biodiversity net gain for major infrastructure projects sits in a different part of the statute book from the regime that applies to planning applications, and it operates on a different timetable. The Environment Act 2021 provides for a biodiversity gain regime for projects consented by development consent order under the Planning Act 2008, built around a biodiversity gain statement issued by the Secretary of State and a biodiversity gain plan approved by the Secretary of State rather than by a local planning authority. The commencement of bng nationally significant infrastructure provisions has been moved more than once, so verify the current position on legislation.gov.uk and gov.uk before relying on any date.

That caveat matters more than any summary of the mechanics. Promoters have programmed survey work against announced dates that then shifted, and the surveys are the part you cannot redo quickly.

How the duty applies to consented infrastructure

The architecture is familiar in outline. A percentage uplift in biodiversity value, measured with the statutory metric against a pre-development baseline, secured and maintained for 30 years, with the gain hierarchy applying so that on-site delivery is preferred, off-site units come next, and statutory credits are the last resort.

What differs is who sets the percentage and who approves the plan. For development consent orders the percentage is set through a biodiversity gain statement made by the Secretary of State for the relevant category of development, and the gain plan is approved as part of the consenting process rather than discharged as a pre-commencement condition by a council.

For the planning application regime, by contrast, the mechanism is a deemed condition on the permission, which is explained in the biodiversity gain condition on every permission.

Differences from the planning application regime

The land assembly difference is the one that changes behaviour. A promoter with compulsory acquisition powers can include land for biodiversity delivery within the order limits, which a planning applicant generally cannot, and that makes on-site and near-site delivery more achievable on a linear scheme than it first appears.

Irreplaceable habitats are treated separately from the metric in both regimes, and the approach to them is set out in irreplaceable habitats and the biodiversity gain exception.

Metric and baseline on a linear scheme

A linear project is a different exercise from a site. The baseline runs for kilometres, crosses dozens of ownerships, and includes habitat parcels you cannot get onto without a notice or a negotiation.

The practical problems are predictable:

• Access for survey across many ownerships, each requiring permission or statutory notice
• Habitat condition assessment over a long corridor, where the surveyor cannot see everything in one season
• Temporary land take for compounds, haul roads and laydown areas, which has a baseline and a restoration value
• Permanent land take for the asset itself, which usually cannot be habitat
• Spatial risk multipliers in the metric, which penalise delivery far from the loss
• Temporal risk, where habitat creation that takes decades to reach target condition is discounted

Treat temporary and permanent land take as separate accounting exercises. Compounds reinstated to a better condition than they started can contribute, but only where the reinstatement is evidenced and secured, and a reinstatement commitment with no management plan behind it will not survive examination.

A Biodiversity Net Gain Assessment with the statutory metric completed by a competent person is the central document, and the regime expects exactly that. The draft is a starting point for the competent person rather than a substitute.

Securing the gain through a development consent order

There is no section 106 agreement in the Planning Act regime. The gain is secured through requirements in the order itself, supported where necessary by side agreements with landowners, conservation covenants or entries on the biodiversity gain site register for off-site units.

Draft the requirements so they can actually be complied with. That means a named plan document with a version number, a trigger for submission and approval, a monitoring and reporting obligation with intervals, and a remedy if target condition is not reached. Requirements drafted loosely at examination become disputes at delivery.

Where off-site units are bought, the register entry and the 30-year management obligation sit with the responsible body or landowner, and the promoter's order requirement has to reference them in a way that survives a change of ownership.

Timing relative to examination

Work backwards from the examination, not forwards from today.

1. Baseline habitat surveys need a growing season, and botanical survey is realistically April to September
2. Protected species surveys have their own windows, which may add another season
3. The metric calculation and the gain strategy follow the surveys
4. Preliminary environmental information is published before the application, so the strategy has to be at least outline by then
5. The application includes the environmental statement and the gain evidence
6. Examination runs on a fixed statutory timetable, and new evidence introduced late is hard to accommodate

A Preliminary Ecological Appraisal at the earliest stage scopes all of that, and on a corridor scheme it is worth doing before the route options are narrowed, because ecology constraints move routes.

Commencement and the position to state

Because the commencement of the infrastructure provisions has shifted, any document you write should carry an explicit statement of the position you have relied on and the date you checked it. That is good practice generally and essential here.

Three things to check at the time of writing: whether the relevant commencement regulations have been made, whether a biodiversity gain statement has been published for your category of development, and what transitional provisions apply to applications already accepted for examination. The PlanScope planning law timeline is a place to follow changes, and the primary sources are the Act and the commencement instruments themselves.

Do not assume that an announced date is in force. And do not assume that because the duty is not yet in force, the examining authority will ignore biodiversity: policy and the environmental assessment regime already require it to be addressed.

Evidence the examining authority expects

Even ahead of the statutory duty biting, a promoter should expect to produce:

• Baseline habitat survey data with survey dates, surveyor names and condition assessments
• The metric calculation with the inputs visible, not just the headline percentage
• Habitat creation and enhancement plans tied to land within or secured outside the order limits
• A habitat management and monitoring plan covering the full 30 years
• An explanation of how the gain hierarchy was applied, with reasons where on-site delivery was rejected
• The draft order requirements that secure all of it

Get the metric inputs reviewed before submission. An examining authority with a competing metric from an interested party will focus on condition assessments and strategic weighting, and those are judgement calls that need to be defensible.

Browse all 66 PlanScope report types to see which documents a corridor scheme is likely to need. For specialist technical reports, qualified professional input may be required.

This is general guidance, not legal advice; check the position with your local planning authority or a qualified professional before relying on it. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.