Downloading the biodiversity metric and version control

The statutory biodiversity metric is a spreadsheet, and the version of that spreadsheet matters as much as the numbers inside it. Defra publishes the tools and their user guides on gov.uk, a validating officer checks which version was used, and a calculation produced in an old version or in a third party summary is a common reason a submission is returned. Download the current tool from the official page at the start of the project, and record the version and the date you downloaded it.

For a self-builder the practical question is which of the published tools applies, and whether the small sites version is available for the scheme.

Where the current tools and guides are published

The metric, the small sites variant, the user guides and the condition assessment sheets are published together by Defra on gov.uk and updated from time to time. Take them from that page rather than from a consultant's file, a forum link or an old email, because superseded copies circulate widely and look identical on the first tab.

Download the whole set. The user guide and the condition assessment sheets are what let you check whether a habitat has been classified and scored sensibly, and they are where the rules that decide your result actually live.

Store the downloaded files with the project record. When the officer asks which version produced the figures, the answer should come from your own file rather than from memory.

Choosing between the full metric and the small sites tool

The small sites metric is a simplified tool for smaller developments, designed so that a scheme can be assessed without the full complexity of the main tool. Eligibility is defined in the guidance and turns on the scale of the development, the site area, and the habitats present, with sites affecting priority habitats or requiring protected species licences generally excluded.

Check eligibility before starting, because moving between tools partway through means redoing the baseline. The criteria are set out in our note on small sites metric eligibility, and the user guide is the authority on the current wording.

Using the small sites tool where the full metric is required will be picked up. Using the full metric where the small sites tool would have been acceptable is not an error, just more work.

Why the version number has to be recorded

Metric versions change the arithmetic. Multipliers, habitat classifications and condition criteria have all been revised between releases, so the same site surveyed by the same ecologist can produce different unit figures in different versions.

Three habits keep this manageable:

1. Record the tool name, version number and download date in the biodiversity gain plan and in any ecology report
2. Use one version throughout a project, from the application stage baseline to the gain plan
3. Where a project spans a version change, say in the submission which version was used and why, rather than leaving the officer to work it out

Authorities generally accept a calculation prepared in the version current when the work was done, provided it is stated. What causes problems is silence.

Reading the user guide and the condition sheets

The condition assessment sheets are the part most applicants skip and most officers check. Each habitat type has criteria, and condition is scored against them by an ecologist on site rather than judged from a photograph.

Read the guidance on strategic significance too, because it draws on local nature recovery strategies and other published plans and it changes the result. Where you are unsure whether an area counts as strategically significant, the local ecology adviser or the authority's ecologist is the right person to ask, and asking early costs less than arguing later.

The guide also sets out the rules on trading between habitat types, which is why a plan proposing to replace a hedgerow with amenity grassland fails regardless of how the areas compare.

What changes between versions and what does not

The framework has been stable: baseline habitats are classified, condition is assessed, units are calculated, and post-development habitats are scored with multipliers for difficulty and time. What changes between versions is the detail, including specific multipliers, classification wording and the treatment of particular habitat types.

The practical effect is that a metric output from two years ago cannot be assumed to hold. If a site was assessed for an earlier application that lapsed, budget for a re-run rather than a cut and paste.

Habitat data also ages. A baseline survey carried out outside the appropriate season, or several years ago, will be questioned by the authority's ecologist whatever version of the tool was used. The metric depends on the survey, so no amount of version control rescues a poor baseline. Finding the designations and habitats near a site before commissioning that survey is worth doing, and our note on using MAGIC to find ecological designations sets out how.

Keeping the audit trail

Version control is only half of it. Keep the survey notes, the habitat plan the areas were measured from, and the file itself in one place, because the same evidence is needed twice: once at application stage and again when the biodiversity gain plan is submitted for approval before development starts.

On a small scheme that gap can be a year or more, by which time the ecologist may have moved firm and the layout may have changed. A complete folder is what lets someone else pick the work up.

Submitting the spreadsheet rather than a summary

Submit the completed tool itself, not a narrative summary of it. Officers open the file, look at the habitat rows, check the areas against the landscape drawings and inspect the condition scores. A report quoting a headline percentage without the calculation behind it will be returned as incomplete.

Two checks before you submit. First, reconcile every habitat area in the spreadsheet with the areas shown on the landscape and layout drawings, because discrepancies here are the single most common query. Second, make sure the file is the one you intended: working copies with test figures get sent by accident, and the officer will read whatever arrives.

The Biodiversity Net Gain Assessment page sets out what the wider assessment covers and how it fits with the other application documents.

Who must complete it and what a draft can do

The biodiversity net gain regime under the Environment Act 2021 expects the statutory metric to be completed by a competent person, which in practice means an ecologist who can classify habitats and assess condition to the published criteria. Habitat classification is a field skill, and the tool assumes the person entering the data has it.

An AI-assisted draft can prepare the narrative that surrounds the metric: the policy context, the description of the site and scheme, the explanation of the approach, and the structure of the biodiversity gain plan. It cannot survey a field, classify a hedgerow or score condition, and it should not be presented as though it can.

PlanScope drafts those narrative documents from your site data and answers and inserts flags where site facts are missing. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval. For the metric itself, the Environment Act 2021 regime expects a competent person, so the spreadsheet is a job for your ecologist.

This is general guidance, not legal advice, and the published tools are updated periodically. Check the current version on gov.uk and confirm local requirements with your local planning authority before relying on any figure. Enter your postcode on PlanScope to see which supporting documents your scheme is likely to need.