Small sites must not be excluded from Biodiversity Net Gain
11th December 2025
Last month, along with more than 80 conservation charities, ecological consultancies and rural businesses, we wrote to the Defra Secretary of State Emma Reynolds, warning against the proposed exemption of small sites from Biodiversity Net Gain (BNG).
Next week, the Government is expected to announce its decision. From what we hear, an exemption for small sites is still on the table.
Under Biodiversity Net Gain (BNG), eligible developments are required to deliver a 10% uplift in biodiversity, from a baseline pre-development state. This can be achieved either through improving habitats onsite or by purchasing offsite ‘units’, which fund habitats created or restored elsewhere.
Government is considering exempting all development sites under 0.5 hectares from the BNG system. It is difficult to believe that a government which recently consulted on expanding the role of the private sector in nature recovery would consider gutting England’s biggest nature market – but that is what this change would amount to.
Small sites make up more than 90% of planning applications, and are responsible for around half of all demand for offsite units. Removing small sites from BNG would reduce access to nature in new developments, weaken a pioneering, world-leading nature market, and undermine nature recovery. An additional exemption for large residential brownfield sites, also rumoured to be under consideration, would greatly exacerbate these problems.
- Southern Damselfly at Cothill Fen, Oxfordshire. Photo copyright Alan S.L. Leung.
By instead setting a 0.1 hectare threshold for inclusion in BNG, and closing the loopholes used on larger sites, Government could deal with the practical challenges of BNG for very small developments, and ensure that housebuilding goals can be achieved, without compromising work to restore our declining habitats.