A biodiversity net gain statement outline for a small site

A small sites biodiversity net gain statement has one job at application stage: to show the authority that you know whether the gain condition applies to your scheme, what the site's starting biodiversity value is, and roughly how you intend to deliver a 10 per cent uplift. The full biodiversity gain plan comes later, after permission and before you start on site. Getting the order wrong is the most common reason a small site stalls, because the baseline habitat survey has a season and the gain plan has a deadline, and neither moves for your programme.

Confirming whether the gain condition applies

Mandatory biodiversity net gain under the Environment Act 2021 works through Schedule 7A to the Town and Country Planning Act 1990, which applies a deemed condition to most planning permissions. It took effect for major development on 12 February 2024 and for small sites on 2 April 2024.

Start the statement by addressing the exemptions, because several of them matter on small sites.

• De minimis development, where the works affect less than 25 square metres of on-site habitat and less than five metres of linear habitat such as hedgerow.
• Householder applications.
• Self-build and custom build development, within the limits set in the regulations on the number of dwellings and the site area.
• Development on a registered biodiversity gain site.
• Certain urgent and Crown development.

Say which exemption you rely on and why, with the figures. A statement that asserts the de minimis exemption without a plan showing the habitat affected and its area will not satisfy an officer, and the self-build exemption in particular has conditions attached that an authority will check.

Where no exemption applies, say so plainly and move on. Half a page settles it.

The small sites route and when it may be used

Where the gain condition applies, the statutory metric has a simplified route for smaller schemes, intended to reduce the survey and calculation burden.

Broadly it is available where the development is not major, the site contains no priority habitat other than hedgerow or arable field margin, and the scheme does not engage the more demanding assessment regimes. The eligibility conditions are set out in the metric's own user guide and are revised from time to time, so state the version of the metric and the user guide you used and confirm eligibility against it rather than from memory.

Where the site has any priority habitat on it, the simplified route is unavailable and the full metric applies. That is worth establishing in the first survey visit, because it changes the cost and the timetable.

Record in the statement: the metric version, the route used, the date of the habitat survey, the surveyor's name and competence, and the eligibility check.

Baseline habitat survey and who can do it

The baseline is the whole exercise. Everything downstream is arithmetic applied to it.

The survey classifies habitats using the recognised UK habitat classification and assesses the condition of each parcel against the published condition criteria. It needs doing at a time of year when the vegetation can be identified, which in practice means the growing season, with April to September the useful window for grassland and other botanical work.

The Environment Act regime expects the statutory metric to be completed by a competent person, and the biodiversity gain plan has to be approved by the local planning authority, so this is one report where professional involvement is legally required rather than advisable. An AI-assisted draft is a starting point for that ecologist, not a substitute for the survey. Where the site has buildings, scrub or mature trees, a Preliminary Ecological Appraisal usually covers the protected species screening at the same visit, which saves a second mobilisation.

Note: a baseline survey carried out after vegetation has been cleared does not help you. Clearance before survey is treated as degradation, and the metric has provisions that apply the pre-clearance baseline where that has happened.

Recording habitat parcels and condition

This is the section the authority reads most carefully, so give it structure.

For each parcel record the habitat type and its classification code, the area in hectares or the length in metres for linear features, the condition assessed against the published criteria with the reasons, the strategic significance applied and the justification for it, and the date of assessment.

Then present it as a table rather than as prose, and present a habitat plan at a readable scale with each parcel numbered to match the table. Officers cross-check the plan against the layout drawing, and a mismatch in site area between the two is the single most common query.

Two further points. State the red line area and confirm it is the same on every drawing. And describe any habitat on the boundary that is retained but affected, such as a hedgerow within the root protection area of construction works, because retained habitat in worse condition after development counts against you.

On site gain through planting and habitat creation

For most small sites the gain comes from converting low-value habitat into something better, and the land available is usually the garden, the margins and the attenuation features.

What tends to work on a plot of a few dwellings: species-rich grassland instead of amenity lawn in the open space, native hedgerow planting along boundaries instead of fencing, individual trees where there is real root space, a wildlife pond where the ground and the safety considerations allow, and lifting the condition of a retained hedgerow through a management regime rather than removing and replacing it.

What does not work: counting narrow strips that will be mown or trampled, planting proposals with no management regime attached, or an uplift that depends on a habitat type that cannot plausibly establish on the soil present. A wildflower meadow specified on a compacted clay subsoil with no soil preparation is a calculation rather than a habitat.

Set out the creation and improvement proposals parcel by parcel with the target habitat type and the target condition, because the metric needs both and the condition target is what the management plan has to deliver.

Off site units and statutory credits as a fallback

Where the layout cannot carry the uplift, the shortfall goes off site.

The route is registered off site units allocated to your development from a parcel on the biodiversity gain site register, secured by a conservation covenant or a planning obligation. Statutory credits sold by government sit behind that as a last resort and are priced to be unattractive.

For the statement at application stage, say what the shortfall is in units, say that off site provision is intended, and say whether a provider has been identified. You do not need the allocation in place to get permission, but you do need it before the gain plan can be approved, which means before you start on site. Agreements in principle that never reach the register are the usual cause of delay.

The trade-offs between the two delivery routes, including the spatial risk reduction applied to distant units, deserve working through before the layout is fixed.

The 30 year management and monitoring commitment

Habitat created or improved has to be maintained for at least 30 years, secured by condition, by a planning obligation or by a conservation covenant.

For a small site that means naming who will do it. A management company funded through estate charges, a residents' arrangement, or the landowner under an obligation are the usual answers, and the authority will want the mechanism rather than an intention. Set out the management prescriptions by habitat type, the monitoring points and intervals, and who reports to whom.

Be realistic about what a handful of households will maintain. A prescription requiring an annual late-summer cut and removal of arisings from a communal meadow is achievable. One requiring quarterly specialist intervention is not.

What goes in at application and what follows

Keep the two documents distinct, because conflating them is what produces a plan that cannot be approved.

At application: the exemption check, the metric version and route, the baseline survey and habitat plan, the pre-development biodiversity value, the proposed post-development value with the creation and improvement proposals, the off-site shortfall if any, and the proposed securing mechanism. That is the statement, and it sits alongside the Planning Statement and the design material described in the design and access statement outline for a minor scheme.

After permission and before development begins: the biodiversity gain plan for the authority's approval, with the completed metric, the habitat details, any allocated off site units, any credits purchased, and the irreplaceable habitat position. The deemed condition prevents commencement until that plan is approved.

A Biodiversity Net Gain Assessment drafted on PlanScope follows this structure and flags the site-specific inputs your ecologist has to supply. Running the submission through a final check against the validation list is worth the hour, and the sequence in the internal quality check covers it.

PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval. For specialist technical reports, qualified professional input may be required.