BNG developments
Back in December 2023 I wrote about the BNG onion - we keep peeling back the layers, but the further we go, the more likely it is to make us weep. Well we’ve just had the Government responses to last year’s consultations on changes to BNG, so get your tissues ready as we peel off the next layer!
There were two consultations: one on changes to minor, medium and brownfield development and the other on bringing Nationally Significant Infrastructure Projects (NSIPs) into the BNG regime. The main news for NSIPs is that the proposed start date is pushed back to 2nd November 2026 in order to give all parties more time to get to grips with the new regime. We’ll publish another blog about this is due course.
For now, here are the key outcomes of the consultation on minor, medium and brownfield development:
1. Introduction of a new exemption for sites of 0.2 hectares or less (so just under half an acre, or 0.4942 acres to be precise). To simplify the regime, the exemption for self-build and custom-build development will be removed, as it is anticipated that most will fall within the area exemption.
This is to be introduced before 31st July 2026.
2. New exemptions for
a. development whose primary objective is to conserve or enhance biodiversity, such as creating ponds - to be introduced “later in 2026”
b. temporary planning permissions granted for a maximum of 5 years - to be introduced before 31st July 2026
c. development enhancing parks, playing fields and public gardens - to be introduced “later in 2026”
3. The biodiversity gain hierarchy for minor development only will be changed so that on-site delivery of BNG is not given preference over off-site delivery. This will be useful for smaller scale development where off-site mitigation might often be the practical answer on constrained sites. To be introduced before 31/7/26.
4. The current excel-based Metric will move to a “digital, integrated service that is more accessible, user-friendly, reliable and data‑driven for all users”. This could be a game-changer (if it works).
5. Changes to the watercourse metric will be explored so that it can be made more proportionate to the level of impact from the development.
6. Changes will be made to the spatial risk multiplier so that off-site units for all types of development can be sourced from anywhere within the same Local Nature Recovery Strategy area on a one-for-one basis. This means that it will no longer be relevant whether the development is in the same Local Planning Authority or National Character Area as the off-site units. This could substantially change the “sphere of influence” for some habitat banks.
7. There is to be a review of the definition of “Open Mosaic Habitat” on brownfield sites. Further changes to BNG on brownfield sites are being considered in a separate consultation which closes on 10th June 2026.
All these proposals will be introduced as part of a package of reforms which will start later in 2026.
Overall, the changes will be broadly welcomed by those dealing with BNG on a day-to-day basis, so not too many tears from the BNG onion this time, but there will inevitably be some confusion about which rules apply as the various proposals are brought into effect over time. We don’t know when exactly the changes to the spatial risk multiplier will come into effect, for example, which could change the areas that developers can source units from and have an impact on the value of units in some places. However, this is all part of the teething pains of a new and novel marketplace and practitioners have already learned to navigate the complexities with care and attention.
As always, the message to those considering dipping a toe in the BNG waters is to take your time, pay attention to the details and ensure you take good advice.
21st April 2026