Biodiversity Net Gain in Sherborne: What We Know So Far
Biodiversity Net Gain has been generating quiet interest in Sherborne for some time. The parish council minutes have carried references to it since September 2024. Earlier this year, the Gloucestershire Local Nature Partnership sent its members a newsletter announcing the first registered BNG site in the county. I wrote a short piece about it for this blog. The response was striking: it attracted about four times the readership of an average post. Clearly, people want to know more.
On Monday I had the opportunity to speak directly with National Trust staff about the BNG project here at Sherborne at their quarterly “drop in session”. What follows is my best account of what I learned. I have shared this draft with the NT to check for factual accuracy before publishing. I should contextualise by saying this scheme is early in its life and there are still, understandably, loose ends here and there.
What is Biodiversity Net Gain?
BNG is a legal requirement introduced under the Environment Act 2022. Developers must demonstrate that any new development leaves biodiversity in a measurably better state than before. Where a development cannot achieve that on-site, it must purchase biodiversity units from a registered off-site habitat scheme. Those units are created and maintained by landowners who commit to managing land for nature over a 30-year period.
The system is designed to channel development money into long-term diverse habitat creation. In principle, it is a sound idea. Personally, I am broadly in favour of it. While there are broader questions nationally about productive agricultural land, it is also clear that farmers are struggling to survive anyway - money going into biodiversity doesn’t necessarily equate to land taken out of agricultural production.
The Sherborne NT Site
National Trust land at Sherborne Farm is being prepared for registration as a BNG offset site. The NT expects registration on the Defra Biodiversity Gain Site Register imminently, possibly within days of this post being written.
The habitat programme involves converting existing arable fields to species-rich grasslands. The NT has already begun preparatory work, funded initially by NT centrally. The establishment cost committed so far is £440,000. Total programme costs are estimated at £1.4 million over the life of the scheme, though the source of funding beyond the initial £440,000 has not yet been fully determined. It may come from BNG credit sales, further NT central investment, or other sources.
Biodiversity units at Sherborne are priced at circa £26,000 per credit. The NT hopes credit sales will repay the initial loan from NT central and contribute to ongoing management costs.
Where Does the Money Go?
This was one of the questions I was asked to raise on behalf of the group. The answer is layered.
NT central has effectively pre-funded the Sherborne project at risk, in anticipation of BNG credit income. The local estate has not funded it independently. Credit income, when it arrives, will flow back toward NT central to repay that loan. Whether any surplus remains with the local estate or flows further into NT's broader finances is not yet clearly settled.
I asked whether the income would be ringfenced to maintain the specific BNG site. The 30-year management obligation means the NT must sustain the habitat condition for three decades. The costs of doing so need to be met from somewhere. NT central appears to be the financial backstop if credit income falls short.
Who Monitors the Scheme?
A Section 106 agreement is in place with Cotswold District Council. CDC will inspect the BNG sites once every five years over the 30-year management period. This is the statutory monitoring arrangement.
Five-yearly inspections are a relatively light touch over a long timeframe. Much can change in a habitat between visits. That said, CDC as the responsible statutory body is a more robust arrangement than some alternatives. The formal legal commitment is real.
Community Benefit
The Gloucestershire Nature and Climate Fund, which acts as broker for BNG credit sales in the county, has stated that any operating surplus will be reinvested in nature and climate projects across Gloucestershire. I asked the NT directly how that community benefit mechanism works in practice.
The honest answer, as I understood it, is that any such benefit would be applied broadly and at GNCF's discretion across the county. There is no mechanism that directs surplus specifically to communities adjacent to offset sites. Sherborne would not automatically see a direct financial return from GNCF's activities here.
That is worth knowing. It does not diminish the conservation value of the scheme. But it is a reasonable distinction to draw.
A Note on the Long View
I asked how the NT budgets confidently for 30-year management costs from a single upfront payment. They seemed reasonably comfortable with their modelling. I am personally less certain that any organisation can forecast land management costs three decades ahead with confidence, given inflation, ecological unpredictability, and potential policy change. The practical answer seems to be that NT central acts as insurer of last resort. For a large and durable organisation, that is a reasonable backstop.
There is also a political question mark, raised by the NT themselves, over whether the BNG framework would survive a change in government. BNG is enshrined in primary legislation, which makes outright repeal unlikely in the short term. But it is not impossible over a 30-year horizon.
An Honest Tension
The NT raised something that I found refreshingly candid. BNG has the potential to be financially significant for large landowners. The NT expects the Sherborne scheme, and others like it, to generate substantial income. But that income comes from developers purchasing credits, and the NT is conscious that some of those developers may be organisations whose activities sit uncomfortably alongside the NT's own conservation values.
Accepting payment from a developer whose project has destroyed habitat elsewhere is, at minimum, a complicated moral position. The NT is aware of this. It is to their credit that they raised it unprompted.
When credits are sold, the Defra register will record which development they are allocated to. That information will be publicly visible. It is worth watching.
Sherborne's Particular Suitability
I asked how Sherborne compared to other National Trust estates in terms of BNG potential. The impression I came away with is that the NT regards Sherborne as particularly well-suited to delivering strong BNG outcomes, relative to many other sites in their portfolio. The combination of existing habitat quality, land type, and landscape character appears to make this estate something of a standout candidate. That is worth noting. It suggests BNG activity at Sherborne may be more significant, and more sustained, than a single scheme implies.
What Comes Next
The Sherborne site should appear on the Defra Biodiversity Gain Site Register shortly, having been accepted yesterday. When it does, the unit count, habitat types, and responsible body will all be confirmed in a public document. We will update the blog when that happens.
In the meantime, I am grateful to the NT staff who gave their time to answer these questions straightforwardly. BNG is a complex mechanism. Understanding how it works locally, and asking reasonable questions about accountability and benefit, seems exactly the kind of thing a catchment support group like ourselves should be doing.
One final observation. I was one of only two members of the local community who attended this quarterly NT session. The National Trust engaged honestly, openly, and candidly on the matters raised. They answered difficult questions without deflection. It would be unreasonable to criticise the NT's communication if the community does not turn up to participate. These briefings exist. Please use them.
