Who may sign a biodiversity gain plan

Nobody signs a biodiversity gain plan in the way a structural engineer signs a calculation. The question of who signs a biodiversity gain plan has a two-part answer: the person with the benefit of the planning permission submits it, and the local planning authority approves it. What sits behind that is the statutory metric, and the metric is where competence actually bites.

That split catches developers out. You can submit a plan yourself and still be refused because the habitat baseline underneath it was assessed by somebody who was not competent to assess it.

What the gain plan has to contain

The biodiversity gain condition is a deemed condition imposed on most grants of planning permission in England by Schedule 7A to the Town and Country Planning Act 1990, inserted by the Environment Act 2021. It became mandatory for major development on 12 February 2024 and for small sites on 2 April 2024, and the position for nationally significant infrastructure projects is set separately, so check where that currently stands.

The condition prevents development beginning until a biodiversity gain plan has been submitted to and approved by the authority. The plan has to set out the pre-development biodiversity value of the onsite habitat, the post-development value, any registered offsite gains allocated to the development, any statutory biodiversity credits purchased, and how the 10 per cent uplift is achieved and maintained for at least 30 years.

The 30 year commitment is the part that changes the paperwork. Habitat of any consequence onsite has to be secured by condition, a section 106 obligation or a conservation covenant, with a habitat management and monitoring plan behind it. A plan that calculates the uplift but says nothing about who maintains the grassland in year 22 is incomplete.

The competent person expectation behind the metric

The statutory biodiversity metric is a Defra tool, published with a user guide and condition assessment sheets. The guidance is explicit that the metric is intended for use by a competent person, and the term is not defined by reference to a register or a licence. It means somebody with the ecological knowledge and field experience to classify habitats and judge their condition correctly.

There is a narrower route for small development. Defra published a small sites metric for use where a scheme meets stated criteria, and that version was designed to be usable without an ecologist in limited circumstances. The user guidance sets out when it cannot be used, including where priority habitats are present or protected species are likely. Read those exclusions before assuming the shortcut applies, because a small sites metric completed on a site it was never meant for is worse than no metric at all.

For anything above that, the practical standard is an ecologist who classifies habitats to the UK habitat classification, assesses condition against the published sheets, and can defend the strategic significance scoring against the local nature recovery strategy. A Biodiversity Net Gain Assessment of that kind requires a competent person as a matter of law under the Environment Act 2021 regime, and an AI-assisted draft is a starting point for that professional rather than a substitute for them.

Habitat condition assessment and its evidence

Condition assessment is the step that moves the numbers most, and it is the step most often done badly.

Each habitat type has its own criteria sheet with a set of pass or fail attributes, and the resulting condition category feeds straight into the unit calculation. A field of species-poor grassland in poor condition and the same field in moderate condition produce materially different baselines, and the only thing separating them is a professional judgement recorded on a sheet.

What a local planning authority ecologist looks for in the evidence:

• a survey date in an appropriate season for the habitats present, with the surveyor named
• habitat parcels mapped to a scale that can be checked against the layout drawing
• completed condition sheets for each parcel, not just the resulting score
• target notes and photographs supporting the condition calls
• a clear statement of any access constraints and what was assessed from the boundary

Where the survey was done outside a sensible season, expect either a precautionary condition assumption or a request to resurvey. Botanical survey work is broadly useful between April and September, so a baseline taken in January is vulnerable.

Who submits the plan and who approves it

The plan is submitted by the person who proposes to carry out the development, which in practice means the developer or their agent. It is approved by the local planning authority, and the authority can ask for revisions before it approves.

That sequence has a programme consequence that still surprises people. Approval happens after permission is granted, not as part of determining the application, so the gain plan sits between permission and the start on site. Where offsite units or credits are needed, the allocation has to be arranged and recorded before the plan can be approved.

Bringing the metric forward into the application is the usual answer. And it costs nothing but sequencing. An authority will not formally approve a gain plan at that stage, but submitting the baseline metric with the application lets the officer check the approach, and it avoids discovering a shortfall after the land deal has completed. The division of responsibility between the person drafting and the person submitting is worth settling in writing, as it is whenever one party writes and another submits.

What professional membership actually signals

No statutory register of biodiversity net gain assessors exists. What the market uses instead is membership of the Chartered Institute of Ecology and Environmental Management, at full or chartered grade, together with evidence of metric work on comparable sites.

Membership signals three things. The member is bound by a code of professional conduct, has demonstrated competence against a published framework, and carries professional indemnity cover through their practice. None of that guarantees a particular condition call is right, and none of it is a licence in the sense that bat work requires a licence. The distinction between competence and licensing runs through ecology work generally, and which ecology licence covers which species activity is a separate question from who may run the metric.

Ask for the assessor's recent metric experience rather than their membership letters alone. Ask, too, whether they will attend a site meeting with the authority's ecologist if the baseline is challenged.

Where liability sits if the baseline is wrong

An overstated baseline is the expensive error, because it inflates the number of units the scheme has to deliver. An understated baseline is the dangerous one, since it understates the uplift required and can leave a development in breach of its own condition.

The regime has an anti-degradation rule to stop baselines being improved by clearance. Where onsite habitat has been degraded since 30 January 2020, the pre-development value is assessed as at immediately before the degradation rather than as found, unless the works were lawful. Clearing scrub in advance of an application is therefore not a strategy.

Contractually, the assessor owes a duty of care to the client who appointed them, and their liability is usually capped by their appointment. The developer still carries the planning consequence, which means a breach of condition notice, an injunction risk and a stalled site. Independent review of the metric before submission costs less than either, and the case for peer review of technical evidence is strongest where the output is a single number everything else depends on.

Briefing an ecologist for the metric alone

Where the scheme is simple and you only need the metric, write the brief tightly: habitat survey and mapping of the application site to the UK habitat classification, condition assessment with completed sheets, baseline and post-development metric calculations in the current statutory version, a trading rules check, and a short note on achievability of the proposed habitat creation.

State the version of the metric expected, name the drawing revision the post-development habitats are taken from, and require the completed metric file rather than only the summary figures. The file is what the authority will interrogate.

Reviewers listed in PlanScope's professional directory can review and sign off AI-drafted ecology documents, and PlanScope's draft is a starting point for that professional rather than a replacement. Enter your postcode on PlanScope to see which reports your site is likely to need.

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