What the data shows so far:
- Just over under 60% (95 of 160) deliver their gain entirely on site. Another 34 use a mix of on-site and off-site measures, while 17 rely wholly on off-site units and 14 did not state an approach. Two bought Statutory Credits.
- Off-site reliance is a recurring theme. A number of plans record an on-site biodiversity loss offset by purchased habitat units — a legitimate route, but one that moves the gain away from the community where the development happens.
- Net gain has to be met habitat type by habitat type (area, hedgerow, watercourse), not as a single blended figure. Several plans that pass overall are marginal — or fall short — on an individual module.
Accessing this data was harder than it should be:
- There is no central register of gain plans – why can’t Defra or Natural England include them in their BGS allocation dataset? These documents should be easily accessible.
- Each council’s portal has to be searched separately, with no consistent way of identifying the relevant application. Only a few authorities (City of York, Bristol and Cotswold among them) have a dedicated application category for BNG discharges. Otherwise the BGPs sit inside generic “discharge of conditions” applications and are very difficult to find.
- BGPs are produced in a variety of forms – as clean PDFs, fillable forms, bespoke versions or scanned images requiring OCR – which is challenging, especially if they are hand-written.
- They are often internally inconsistent: off-site figures just copied from the on-site section, credits confused with habitat-bank units, or headline numbers that do not reconcile.
- Off-site claims frequently differ from what the Biodiversity Gain Sites register records as allocated.
- Many applications do not include the required BNG Metric calculation.
- Some applications can’t be analysed because all that is produced (and approved) is the certificate of the off-site HU purchase – and sometimes not even that. As a result, we’ve been unable to include these in our analysis.
The information exists, but we can only conclude that the planning approval process makes meaningful public scrutiny far harder than it needs to be. Using the available standard Defra form and creating a single searchable register of BGPs would be a straightforward improvement.
The full dataset and analysis are here — comments, corrections and more data are welcome:
NB. This analysis will grow as we add more data.
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Bristol Tree Forum 