Thirty year management and monitoring under BNG

The 30 year requirement under biodiversity net gain is the part that turns a one-off assessment into a long term land management commitment. Where a scheme delivers substantial on-site habitat improvement, or buys off-site units, that habitat has to be maintained and monitored for at least 30 years, secured by a planning obligation or a conservation covenant, with a habitat management and monitoring plan setting out who does what and when.

Thirty years is longer than most development companies hold a site and considerably longer than most management contracts. That mismatch is the practical problem the regime creates, and it needs answering at application stage rather than at discharge of conditions.

What the thirty year requirement covers

The biodiversity gain condition is deemed to be attached to most planning permissions in England under Schedule 7A to the Town and Country Planning Act 1990, inserted by the Environment Act 2021. Development cannot lawfully begin until the local planning authority has approved a biodiversity gain plan showing a gain of at least ten per cent measured on the statutory metric.

The 30 year duration attaches to the habitat, not to the permission. It applies to significant on-site enhancements and to off-site gains registered against the development. It does not apply to retained habitat that was already there and is simply not being harmed, and it does not apply to on-site works the metric treats as minor.

So the first question on any site is which parcels of your proposed habitat are carrying a 30 year obligation and which are not. The metric output tells you, and the answer usually changes the landscape design.

How habitat is legally secured

There are two routes, and the choice has consequences for cost, flexibility and who ends up responsible.

A planning obligation under section 106 of the 1990 Act binds the land and is enforceable by the local planning authority. It is familiar, it can carry payment obligations and step-in rights, and it sits with the rest of the agreement.

A conservation covenant under Part 7 of the Environment Act 2021 is an agreement between a landowner and a designated responsible body. It also binds successors in title, and it is the usual mechanism for off-site habitat banks because the responsible body, rather than a planning authority with other priorities, holds the enforcement role.

Conditions alone will not do the job for a 30 year commitment, because a condition cannot require payment and the authority's practical remedies against a dissolved developer are thin.

The management and monitoring plan

The habitat management and monitoring plan is the operational document. It names the habitat parcels and their target condition on the metric, sets out the establishment works, the annual management operations, the monitoring regime, the reporting route and the remedial actions available if a parcel is failing.

Write it as an instruction to whoever will hold the land in year 18, not as a planning document. That means plain management prescriptions with months and frequencies: cut dates for a meadow, grazing densities and periods, scrub control cycles, tree and hedge maintenance, and what is specifically not to be done.

The monitoring pattern most plans adopt is a survey in each of the first five years, then at roughly five yearly intervals to year 30, with a condition assessment against the metric criteria and a written report to the authority or the responsible body. That is the usual approach rather than a statutory rule, so check what the authority expects locally.

A Biodiversity Net Gain Assessment sits upstream of all of this, and the habitat baseline it rests on comes from an ecological survey. Biodiversity net gain under the Environment Act 2021 expects the statutory metric to be completed by a competent person and the gain plan to be approved by the authority, so an AI-assisted draft is a starting point for that professional rather than a substitute for them.

Who carries out monitoring

Condition assessment against the metric criteria is ecological survey work, so it needs a suitably qualified ecologist. A grounds maintenance contractor cannot assess whether a grassland parcel has reached moderate condition.

On larger schemes the arrangement that works is a management company or a land trust holding the land and the funding, with an ecologist appointed to the monitoring role under a long term agreement. On small sites the obligation often falls back on individual householders, which is where the regime is weakest, because a rear garden hedgerow parcel managed by whoever buys plot seven in year 12 is a fragile proposition.

Be honest about that in the plan. An authority is more likely to accept a design that puts the 30 year parcels in a single managed area than one that scatters them across private gardens.

Costs and who bears them

The cost components are establishment works, annual management, monitoring surveys and reporting, administration of the management body, and a contingency for remedial works. On off-site units the provider prices all of that into the unit price and takes the risk.

On-site delivery looks less expensive at the outset and carries the long tail. Someone has to pay for year 22, and if that someone is a residents' management company funded by service charge, the charge has to be set at a level that survives three decades of inflation and resale.

Where the authority requires financial security, expect a bond, a cash deposit or a stepped payment schedule. Those terms are negotiated in the section 106 agreement, and they are worth the drafting time.

A Landscape Strategy and, on larger schemes, a Green Infrastructure Plan should be drawn up alongside the habitat plan rather than after it, because a planting scheme designed for appearance and a habitat parcel designed for metric condition pull in different directions.

Failure and remedies

If a parcel is not reaching its target condition, the plan should already say what happens: a review, a revised management prescription, replacement planting, or in the worst case the purchase of off-site units or statutory credits to make up the shortfall.

The legal remedies depend on the route. A breach of a section 106 obligation is enforceable by the authority, including by injunction and, where the agreement provides for it, by drawing on a bond or exercising step-in rights. A conservation covenant is enforceable by the responsible body against the current owner.

What nobody has much experience of yet is year 25. The regime is young, the first monitoring cycles are only now producing data, and how authorities respond to a parcel that has quietly failed is untested. Plan for the possibility that enforcement becomes more active, not less.

The honest uncertainty is worth stating in your own documents. An obligation drafted with a realistic remedial mechanism is easier to defend than one that assumes the habitat will simply work.

To see which ecological and landscape documents a scheme is likely to need, browse all 66 PlanScope report types, and start the ecology work with a Preliminary Ecological Appraisal before the layout is fixed.

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