The 30-year BNG obligation: who signs what

Biodiversity gains have to be maintained for at least 30 years, and the question of who signs what has three answers depending on where the habitat sits. On-site enhancements are secured by planning condition or by a section 106 obligation between the developer, the landowner and the council. Off-site gains are secured either by a conservation covenant between the landowner and a designated responsible body, or by a section 106 agreement. In every case a habitat management and monitoring plan sits behind the legal document and does the real work.

The 30 year BNG management period is long enough that the parties signing today will mostly have moved on before it ends. That is why the mechanism has to bind successors rather than people.

Why the regime asks for 30 years

Habitats take time. A species-rich grassland created from arable ground needs years of the right cutting and grazing regime before it resembles the target condition the metric assumed, and a new woodland needs far longer.

Thirty years is the statutory minimum written into the biodiversity gain framework under the Environment Act 2021 and Schedule 7A of the Town and Country Planning Act 1990. It is a floor, not a ceiling, and some authorities and some habitat bank operators secure longer.

The period runs from the completion of the works creating or enhancing the habitat, so a phased scheme can have several start dates. Set out in the management plan which parcel starts when, or the monitoring schedule becomes impossible to administer.

Conservation covenants and responsible bodies

A conservation covenant is an agreement between a landowner with a qualifying interest and a body designated by the Secretary of State as a responsible body. It binds successors in title and is registered as a local land charge.

Three practical points decide whether this route works.

The landowner must have a sufficient interest for the length of the covenant, which is where leasehold and short tenancies cause problems. A tenant farmer cannot bind land beyond their own interest.

Any lender with a charge over the land needs to consent, because the covenant affects the security. This is the single most common cause of delay, and it should be started weeks before anyone expects to sign.

And the responsible body has to agree to take it on. The list of designated bodies is published by government, and each one has its own criteria, its own fee structure and its own appetite. A body that manages heathland may not want a small urban grassland parcel.

The background to the mechanism itself is set out in the note on conservation covenants under the Environment Act 2021.

Section 106 as the alternative

A planning obligation under section 106 of the 1990 Act does the same job through a different route. The agreement is between the council and everyone with an interest in the land, and it runs with the land so that successors are bound.

Its advantage is familiarity. Councils know how to draft, monitor and enforce them, and the applicant's solicitor has done a hundred of them. Its disadvantage is that the local authority becomes the enforcing party for three decades, and monitoring capacity in planning departments is thin.

Where the off-site land lies in a different authority's area from the development, a section 106 gets awkward, because the council enforcing the obligation has no jurisdiction over the land. That is the case where a conservation covenant usually wins.

Whichever route is chosen, a condition on the permission alone does not secure off-site land, because the council cannot condition land outside the application site in a way that binds a third party.

What the management and monitoring plan contains

The habitat management and monitoring plan is the operational document, and the legal agreement should annex it rather than paraphrase it.

It should record the baseline habitat and condition as assessed in the metric, the target habitat and target condition for each parcel, and the year by which each target is to be met. Then the prescriptions: cutting dates, grazing regimes, stocking densities, scrub control, tree maintenance, water level management, and what is not to be done.

After that, the monitoring schedule. State which years carry a survey, who carries it out and to what method, what is measured, and who receives the report. Monitoring is typically more frequent during the establishment years and at longer intervals afterwards, and the register entry records the agreed schedule.

Finally the remedial mechanism. Say what happens when a parcel misses its condition target at a monitoring point, and give a defined period to put it right before any enforcement step.

Money and who carries the cost

Thirty years of management, monitoring and reporting costs real money, and the metric takes no view on whether anyone has set it aside.

Deal with it explicitly. Options include a capital sum paid to the responsible body or land manager at the outset, a bond or escrow arrangement, a service charge on the development where a management company is involved, or an income-generating use of the land compatible with the habitat.

Councils increasingly ask for evidence of the funding arrangement before signing the agreement, and a gain plan that assumes the landowner will absorb the cost out of goodwill is not evidence.

Transfer of land during the period

Both mechanisms bind successors, so a sale does not end the obligation. What a sale does do is create practical risk.

Make sure the covenant or obligation is properly noted on the title so that a buyer's solicitor finds it. Require the outgoing owner to hand over the management plan and the monitoring record, and consider a positive obligation to notify the responsible body or the council on transfer.

Where the land is sold in parcels, the plan needs to work parcel by parcel. A management prescription that depends on grazing the whole holding as one unit falls apart when half of it changes hands.

What happens if management fails

Under a conservation covenant, the responsible body can enforce, with remedies including an order requiring performance and damages applied to putting the habitat right.

Under a section 106, the council can enforce through the courts, including by injunction, and can carry out works itself and recover the cost in some circumstances.

Behind both sits the biodiversity gain condition on the permission itself. The gain plan has to be approved before development may lawfully start, and a plan that relies on off-site land which is not yet registered and allocated is not an approvable plan. That sequencing is the discipline that makes the rest of it work.

Commission the ecology early so the securing mechanism can be built alongside the design. A preliminary ecological appraisal in the right season tells you how much of the requirement the site itself can carry, and the Biodiversity Net Gain Assessment must be completed by a competent person under the Environment Act 2021 regime, with an AI-assisted draft serving as a starting point for that person rather than a substitute. Enter your postcode on PlanScope to see which ecology documents a site is likely to need.

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.