BNG operates through two layers of legal mechanism: the planning condition that attaches to the permission, and the legal agreements that secure delivery over 30 years. Understanding how these fit together matters because each does different work, and gaps in either can create problems.
When a local planning authority grants planning permission for a development subject to BNG, the permission automatically includes a biodiversity gain condition. This isn't discretionary—Schedule 7A of the Town and Country Planning Act requires it.
The condition has a specific function: it prevents development from lawfully commencing until the LPA approves a Biodiversity Gain Plan. The Gain Plan must demonstrate how the development will achieve at least 10% net gain, showing baseline calculations, proposed habitat measures, and how any off-site units or credits are secured.
This makes BNG a pre-commencement condition. A developer can hold a valid planning permission and still be unable to start work. If the Gain Plan isn't approved—because the numbers don't add up, because off-site arrangements aren't properly evidenced, because the 30-year management isn't secured—the condition isn't discharged and groundworks can't begin.
LPAs have eight weeks to determine whether a Biodiversity Gain Plan is satisfactory. In practice, getting to approval often requires back-and-forth on details, particularly around legal security for off-site delivery.
The planning condition ensures that BNG is addressed before development starts. But a condition attached to a planning permission doesn't, by itself, bind land for 30 years or create enforceable management obligations.
For on-site habitat delivery, the condition might be sufficient if the habitat areas are within the development site and the obligation runs with the land through the planning permission. But even then, LPAs often want additional security—particularly for habitat management and monitoring over three decades.
For off-site delivery, conditions can't do the job at all. The planning permission applies to the development site, not to land elsewhere. If biodiversity units are being generated on a separate parcel—a habitat bank, a farmer's field, a conservation project—that land needs its own legal mechanism to secure the 30-year commitment.
This is where legal agreements come in.
Section 106 of the Town and Country Planning Act 1990 allows planning obligations to be attached to land. These are contractual agreements between the developer (or landowner) and the local planning authority, and they run with the land—meaning they bind future owners, not just the original signatory.
For BNG, section 106 agreements typically cover:
Section 106 agreements are enforceable by the LPA. If the landowner or their successors don't deliver, the authority can pursue breach of the agreement, potentially seeking injunctive relief through the courts. This gives the commitment teeth that a bare planning condition lacks.
For on-site BNG, the section 106 might secure habitat areas within the development. For off-site BNG, there will typically be a section 106 (or equivalent) on the receptor site where the habitat is being created.
The Environment Act 2021 introduced conservation covenants as an alternative mechanism, specifically designed for long-term conservation commitments. These are agreements between a landowner and a "responsible body"—which might be Natural England, a local authority, or certain conservation charities like Wildlife Trusts or the National Trust.
Conservation covenants work similarly to section 106 agreements in that they bind the land and run with successive owners. But they have some differences:
Enforcement sits with the responsible body, not necessarily the LPA. This means a conservation organisation can directly enforce the covenant if habitat management lapses, without relying on council enforcement resources.
They're designed for conservation purposes, so the legal framework is tailored to habitat management rather than being adapted from general planning obligation provisions.
Registration requirements apply. Off-site BNG land secured by conservation covenant must be registered on the Biodiversity Gain Sites Register maintained by Natural England. This creates a public record of where units are being generated and prevents double-counting.
For habitat banks and off-site BNG providers, conservation covenants are becoming the standard mechanism. They provide the security that developers and LPAs need, with enforcement by bodies that have conservation expertise and motivation.
Whether through section 106 or conservation covenant, the legal agreement securing BNG needs to address several things:
Location and extent of the habitat—exactly which land, mapped and referenced.
Baseline and target condition—what the habitat is now, what it needs to become, and how that translates into biodiversity units.
Management prescriptions—the specific works required to create or enhance habitat and maintain it over 30 years. This might include grazing regimes, cutting schedules, scrub control, water level management, or other interventions depending on habitat type.
Monitoring and reporting—how often the habitat will be assessed, what metrics will be used, and who receives the reports. Many agreements require professional ecological monitoring at intervals (often years 2, 5, 10, 20, and 30).
Financial security—how management will be funded for 30 years. This might involve upfront payments into a management fund, bonds, or other mechanisms to ensure money is available even if the original parties disappear.
Remediation provisions—what happens if the habitat underperforms. If monitoring shows the target condition isn't being achieved, the agreement should specify what corrective action is required.
Allocation of units—for off-site delivery, which development the units are allocated to, ensuring they can't be sold twice.
The legal agreements create enforceable obligations, but enforcement requires someone to act.
For section 106 agreements, that's the local planning authority. LPAs have enforcement teams, but these are often stretched—the Local Government Association has noted concerns about capacity for BNG monitoring. Whether authorities will actively pursue breaches 15 or 20 years after a development completes remains to be seen.
For conservation covenants, the responsible body has enforcement powers. Conservation charities may be more motivated to pursue habitat management failures than council enforcement teams with competing priorities. Natural England can also take action where it holds covenants.
The strength of enforcement is one reason why the quality of the legal agreement matters. A well-drafted agreement with clear obligations, measurable standards, and realistic remediation provisions is easier to enforce than vague commitments. And agreements that include financial security—bonds, management funds, guarantees—provide a route to remedy even if the landowner won't or can't perform.
EcoCapital structures off-site BNG delivery with legal agreements designed to satisfy LPA scrutiny and stand up over 30 years. Units are secured through conservation covenants registered with Natural England, with management and monitoring frameworks built in from the outset.
For developers, this means the paperwork required to discharge the biodiversity gain condition is already in place—unit allocation, legal security, and evidence of 30-year management. For landowners providing habitat bank land, Eco Capital handles the covenant arrangements and ongoing management obligations.
