The 30 January 2020 BNG baseline and degraded land
Where habitat was cleared after 30 January 2020 without the consent it needed, the biodiversity net gain baseline reverts to the value immediately before that clearance.
If habitat on your site was cleared, ploughed, sprayed or stripped after 30 January 2020 without the permission or consent it needed, the biodiversity net gain baseline is not what the ecologist finds on site today. Schedule 7A to the Town and Country Planning Act 1990, inserted by the Environment Act 2021, lets the pre-development biodiversity value be taken as the value immediately before those activities were carried out. In practice that means you buy the 10 per cent gain on the habitat that was there, not on the bare ground you are standing on.
That date is not arbitrary. 30 January 2020 is the day the Environment Bill was introduced to Parliament, so the provision reaches back to the moment the regime became public knowledge.
Why an earlier baseline date exists
Mandatory biodiversity net gain applies to most planning permissions granted after 12 February 2024 for major development and 2 April 2024 for small sites, with a 10 per cent uplift measured in the statutory metric and secured for at least 30 years. The obvious way to cheat it is to flail a species-rich grassland or grub out a hedgerow before applying, so that the baseline is low and the gain is easy.
The degraded land provision closes that route. Where the authority is satisfied that activities carried out after 30 January 2020 reduced the biodiversity value of the onsite habitat, and that those activities were not carried out in accordance with a planning permission or other required consent, the earlier value is used. The applicant does not get the benefit of the clearance.
Two features of the drafting are worth holding onto. It is not limited to deliberate acts aimed at the metric, and it is not limited to acts by the current landowner. A previous owner's clearance in 2021 can set your baseline.
How the rule treats clearance before application
The test is about the activities and their effect, not about motive. Mowing a wildflower meadow to a short sward, scraping topsoil for a temporary compound, tipping inert material over a wet ditch, spraying off a hedge bank, felling a group of trees outside a Tree Preservation Order area: each could reduce measured biodiversity value in the metric, and each is capable of engaging the provision.
What takes an activity outside the rule is lawful authority. Routine agricultural operations that need no consent, works carried out under a planning permission, and operations covered by another required consent sit outside it. The line between ordinary farming and a reduction in value is where most arguments happen, and it is a question of fact for the authority.
A practical consequence for the ecologist: the baseline survey is no longer only a description of what is present. It becomes a reconstruction exercise, and the report needs to say which condition and distinctiveness scores were assigned to the reconstructed habitat and on what evidence. Our note on reviewing another consultant's ecology report sets out what to interrogate in that kind of assessment.
Evidence an authority will ask for
Expect the planning officer, advised by the county ecologist, to want the reconstruction evidenced rather than asserted. The usual package is:
- dated aerial or satellite imagery from before and after the activities, with the source and capture dates stated
- any previous ecological survey of the site or of adjoining land, including surveys commissioned for an earlier scheme
- Historic Environment Record and local records centre data for habitats and species
- the local authority's own habitat mapping or Phase 1 habitat survey data where it exists
- statements from the landowner or occupier about what was done, when, and under what authority
- soil and seed bank evidence where a grassland is claimed to have been more diverse than the current sward suggests
Where the evidence is thin, authorities tend to resolve doubt against the applicant, because the statutory structure puts the burden on the applicant to show the pre-development value. Build the file before you apply.
Aerial imagery and historical records
Imagery is the workhorse. Google's historical imagery, the Environment Agency's LiDAR and aerial photography on the open data portal, and commercial satellite archives give a reasonable sequence for most sites, though cloud cover and capture intervals leave gaps. Resolution is good enough to show that a hedgerow existed, that a field was permanent pasture rather than arable, or that scrub covered a corner of the site.
Imagery alone will not give you a condition score. A grassland that looks uniform green from 400km up could be a modified grassland in poor condition or an other neutral grassland in moderate condition, and the difference in units is substantial. That is why the records search matters: a 2018 extended Phase 1 survey for a withdrawn application is worth more than any amount of imagery.
An illustrative example. A 3.2ha field on the edge of a market town was mapped in a 2019 appraisal as other neutral grassland in moderate condition. In 2022 it was ploughed and reseeded as a ryegrass ley. On an application in 2026 the metric baseline would be modified grassland in poor condition, but the degraded land provision pulls the baseline back to the 2019 habitat, and the required gain rises accordingly. The figures in that example are illustrative, and the actual unit values would come from the statutory metric run by a competent person.
Where the rule does not apply
The provision has limits, and knowing them saves unnecessary cost.
| Situation | Effect on baseline |
|---|---|
| Clearance before 30 January 2020 | Today's habitat is the baseline |
| Works carried out under a planning permission | Today's habitat is the baseline |
| Operations under another required consent | Today's habitat is the baseline |
| Natural change, flood, fire or disease | Not an activity carried out by a person |
| Clearance after 30 January 2020 without required consent | Earlier value applies |
Natural loss is the interesting category. Ash dieback that removes a treeline, or a river that takes a bank out, is not an activity carried out on the land in the relevant sense, although an authority may still ask hard questions about timing. Where you are relying on natural causes, document them contemporaneously, because retrospective explanation reads badly.
Development exempt from the biodiversity gain condition altogether, such as certain small householder applications and some permitted development, does not reach the baseline question at all.
Effect on the gain calculation
The arithmetic consequence is larger than people expect. The 10 per cent uplift is measured against the baseline, so a higher baseline raises both the number of units you must replace and the number you must add. Habitat creation on the developed site is usually constrained by layout, so the shortfall goes off site or into statutory credits, and statutory credits are priced to be the least attractive option.
The sequence to work through, once the baseline is settled:
- Run the statutory metric on the reconstructed baseline, documenting the assumptions.
- Maximise onsite retention and creation within the layout, taking account of the trading rules on distinctiveness.
- Scope off-site units, bearing in mind that the spatial risk multiplier discounts units further from the development.
- Treat statutory credits as the fallback, not the plan.
- Draft the biodiversity gain plan with the baseline evidence attached, because the authority has to approve it after permission is granted.
Our explainer on soil translocation and habitat creation on stripped ground covers the practical side of rebuilding value on a site that has already been cleared, and the overlap with hedgerow protection is dealt with in hedgerow units and the Hedgerows Regulations.
Avoiding the problem on acquisition
For anyone buying land, this is now a due diligence item with a price attached. Add three things to the pre-acquisition checklist. Commission a desk-based baseline review covering imagery from early 2020 onwards. Ask the vendor for a written statement of operations carried out since 30 January 2020 and the consents relied on. Where the land has been cleared, price the metric consequence into the bid rather than discovering it at the biodiversity gain plan stage.
If you are the one managing land you expect to develop, keep a dated record of every operation and the authority for it. A farm diary and a folder of agri-environment paperwork is unglamorous evidence that answers the question in one meeting.
A biodiversity net gain assessment under the Environment Act 2021 regime expects the statutory metric to be completed by a competent person and the biodiversity gain plan to be approved by the local planning authority, so an AI-assisted draft is a starting point for that professional rather than a substitute for them. 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.
Frequently asked questions
What is the 30 January 2020 rule in biodiversity net gain?
It is the degraded land provision in Schedule 7A to the Town and Country Planning Act 1990, inserted by the Environment Act 2021. Where activities carried out after that date, without the planning permission or other consent they required, reduced the biodiversity value of the site, the pre-development value can be taken as the value immediately before those activities. The date is when the Environment Bill was introduced.
Does the rule only apply if clearance was deliberate?
No. The statutory test turns on whether activities reduced the biodiversity value and whether they were carried out in accordance with a required consent, not on motive. It also is not limited to acts by the current owner, so clearance by a previous owner in 2021 can set the baseline for an application made years later.
What evidence shows what the habitat used to be?
Dated aerial and satellite imagery with stated capture dates, any earlier ecological survey of the site or adjoining land, local records centre and Historic Environment Record data, council habitat mapping, landowner statements about operations and consents, and soil or seed bank evidence. Imagery alone rarely supports a condition score, so earlier survey data is the most valuable item.
Does normal farming trigger the degraded land provision?
Routine agricultural operations that need no consent sit outside the provision, and so do works carried out under a planning permission or other required consent. The boundary between ordinary farming practice and an activity that reduced biodiversity value is a question of fact for the authority, and it is where most disputes arise.
How does a higher baseline change the gain I must deliver?
The 10 per cent uplift is measured against the baseline, so a higher baseline increases both the units you must replace and the units you must add. Onsite creation is usually limited by layout, which pushes the shortfall off site or into statutory credits, and statutory credits are deliberately priced as a last resort.
How do I protect myself when buying land?
Commission a desk-based baseline review using imagery from early 2020 onwards, ask the vendor for a written statement of operations carried out since 30 January 2020 and the consents relied on, and price the metric consequence into the bid where clearance has occurred. Discovering the issue at biodiversity gain plan stage is far more expensive.
Sources and further reading
This article is general guidance about the planning system in England and, where stated, the rest of the UK. It is not legal or professional advice. Check your local planning authority’s validation requirements and take professional advice for your specific site.