Competent person rules and biodiversity net gain drafts

A biodiversity net gain competent person is not a formality bolted onto the paperwork. The statutory metric requires habitat parcels to be identified, mapped and condition assessed against published criteria, in the field, at the right time of year. No amount of drafting skill substitutes for that. What a drafted document can do is assemble everything around the ecology: the policy framing, the site description, the programme, the gain plan structure and the questions your ecologist needs answered.

Understanding where that line falls saves money, because it stops you paying consultant rates for narrative and it stops you submitting a metric nobody competent has stood behind.

What the regime requires of the author

Mandatory biodiversity net gain arrived under the Environment Act 2021, which inserted the biodiversity gain condition into the Town and Country Planning Act 1990. It applied to major development from 12 February 2024 and to small sites from 2 April 2024, with exemptions including householder development and certain self-build schemes.

The condition works by deeming a pre-start requirement onto most planning permissions: development may not begin until the local planning authority has approved a biodiversity gain plan showing at least a 10 per cent uplift against the pre-development baseline, secured for 30 years.

The baseline and the uplift are both calculated with the statutory biodiversity metric published by Defra. The metric guidance is explicit that it should be applied by a person with the ecological competence to use it, because almost every input is a judgement about habitat type and condition rather than a measurement anyone can take.

Why habitat condition cannot be assessed from a desk

Habitat type might sometimes be inferred from aerial imagery. Condition cannot.

The metric's condition assessments ask about sward structure, the proportion of undesirable species, bare ground, litter accumulation, evidence of management, hedgerow gaps, height and width, canopy connectivity and a dozen similar field observations. Each criterion is scored on site by someone who knows what they are looking at, and the difference between good and moderate condition on a single parcel can move the unit total enough to change the whole strategy.

Timing matters as much as skill. Grassland assessed in February tells you very little about species richness, and an assessment run outside the botanical season will be challenged by the authority's ecologist.

The seasonal windows are unforgiving on a development programme. Botanical survey work runs roughly April to September. Bat emergence surveys run May to September. Great crested newt environmental DNA sampling runs from mid-April to the end of June. Miss the window and the metric waits a year, or it goes in on assumptions that a reviewer will discount.

That is the practical reason a Preliminary Ecological Appraisal usually comes first. It establishes what is present, and it sets the survey programme that the metric work then depends on.

What a draft can genuinely prepare

Plenty, as it turns out. A biodiversity gain plan is mostly structured narrative around a small core of calculated numbers.

• The site and development description, including the red line area and the phasing.
• The policy and legal framing: the gain condition, the relevant local plan policy, the authority's own net gain guidance.
• The application of the mitigation hierarchy in plain terms, explaining what was avoided, what was minimised and what is being compensated.
• The 30-year management and monitoring narrative, with the reporting intervals set out.
• The programme showing when surveys run and when the plan is submitted.
• A schedule of the facts the ecologist still needs to supply, flagged rather than guessed.

That last point is the useful one. A draft that inserts a clear placeholder where a habitat unit figure belongs is doing its job. A draft that invents a plausible figure is worse than no draft at all, and it wastes the reviewer's time on correction rather than judgement.

The parts only the ecologist can complete

The metric itself, obviously. Also the habitat classification to UK Habitat Classification, the condition assessments, the strategic significance judgement, the difficulty and time-to-target multipliers, and the professional sign-off that the outputs are sound.

Irreplaceable habitat is its own category. Ancient woodland, lowland fen, blanket bog and similar habitats sit outside the metric trading rules and need bespoke compensation agreed with the authority and Natural England. A drafting tool can flag that a designation appears in the desk data. It cannot design the compensation.

Where protected species are involved, a separate legal threshold applies: surveys and any mitigation licence require a suitably licensed ecologist under the Wildlife and Countryside Act 1981 and the Conservation of Habitats and Species Regulations 2017.

A Biodiversity Net Gain Assessment is a report type where a competent person is legally required, and an AI-assisted draft is a starting point for that professional rather than a substitute for them.

Getting the sequence and the programme right

The most expensive mistake is leaving ecology until the planning application is drafted.

1. Commission the ecological appraisal early, in the season that suits the habitats present.
2. Fix the baseline date and record it, because the pre-development value is normally taken at the date of application.
3. Run the metric on the baseline before the layout is fixed, so the design can respond to where the units are.
4. Design the on-site gains into the scheme, then test the residual shortfall.
5. Investigate off-site units or statutory credits only after the on-site position is settled.
6. Draft the gain plan narrative in parallel, leaving the calculated figures to the ecologist.

There is a trap in step 2. Habitat degraded after 30 January 2020 can be assessed at its pre-degradation value, so clearing a site to simplify the baseline achieves nothing except a worse starting point and a difficult conversation. The note on habitat units as the currency of biodiversity net gain explains how the trading rules then constrain what a shortfall can be made up with.

What happens when the metric is unsupported

Authorities check. Many have retained an ecologist or use a county ecology service, and the first thing that person opens is the condition assessment.

A metric submitted without field condition assessments, or with habitat types that do not match the site, gets one of three responses: a request for further information that stops the clock, a refusal to approve the gain plan, or approval followed by a condition discharge dispute at the worst possible moment, when the contractor is mobilised and the gain plan is the only thing standing between you and a lawful start.

None of those outcomes is recoverable by better drafting. They are recoverable by booking the survey.

There is a reputational dimension too. Authorities remember which agents submit metrics that hold up. On a second application in the same borough, a gain plan from a team whose last one was sound moves through consultation noticeably faster than one from a team whose last one was withdrawn.

See PlanScope pricing for the report tiers, and the professional directory for the review route when your draft needs a competent person to check and sign it.

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. For specialist technical reports, qualified professional input may be required.