Defra has updated its guidance on changes to Biodiversity Net Gain policy governing small, medium and brownfield developments. We run though the key points.
Taking in more than 25,000 responses to an eight-week consultation which began in May 2025, the Department for Food & Rural Affairs published details of a refined and streamlined BNG policy late last year. This was met with some criticism at the time, although amendments did not go as far as some sceptics had feared.
Last week, new guidance was shared on exactly what these changes mean. This includes confirmation of exemption for development sites which are less than 0.2 hectares. Although projects at that scale may appear to be relatively innocuous, this change alone means 50% of new residential buildings are likely to escape the requirements enforced by BNG regulations.
For organisations that oversee and administer contributions, this is expected to lead to a 12% fall in baseline biodiversity units used to compensate under mandatory rules. Off-site demand will also drop by around 10%. A separate consultation on residential brownfield developments will guide how the so-called de minimis exemption will work going forward. This applies to sites which have no priority habitats present and work that will impact less than 25 m2 or less than 5m of linear features. In contrast, some previous exemptions are due to end — namely self-build and custom applications.
Other sites that will not be covered by BNG regulations include developments where the primary goal is conserving or enhancing biodiversity. More controversially, temporary planning permits will also fall outside the law. Defra argues this is due to the limited scope for nature recovery in five years or less. Improvements to parkland, playing fields, and public gardens will not need to comply, either.
Changes abound when it comes to metrics, too. Perhaps most importantly, there will be a move away from the existing Excel-based platform, with a new integrated digital service launching specifically for BNG measurement tools. The government is now considering a number of measures that can help support small and medium enterprises navigate this decision. New approaches to watercourse metrics are also being assessed. In particular, the following proposals are on the table:
- Explore and test whether a simplified condition assessment could reduce costs, lessen burdens, and save time while retaining ecological integrity
- Consider how the simplified condition assessment would work alongside the existing RCA
- Explore whether adding a new distinctiveness category for heavily modified watercourses could help ease BNG pressures for sites, particularly where achieving ecological improvements on heavily modified or constrained watercourses is challenging
BNG hierarchy has also been addressed in the update. ‘We will use regulations to amend the biodiversity gain hierarchy for minor development only, where it is not already exempt. This will place off-site biodiversity gains on the same preference as enhancement and creation of onsite habitat,’ a Defra spokesperson explained. ‘The other elements of the biodiversity gain hierarchy will remain in place, with statutory credits remaining the last resort option. Many respondents expressed support for the importance of the mitigation hierarchy, and the principles of first avoiding then mitigating the adverse effects of development remain.’
Moving forward, Local Nature Recovery Strategy [LNRS] areas will be subject to spatial risk assessments. These will not be required in locations that are not covered by these plans, although this could change following local government reorganisation at a later day. Finally, a consultation to seek views on a targeted exemption for brownfield residential development is now underway to consider factors such as open mosaic habitats.
‘These announcements send a strong and welcome signal that Government is listening and acting on industry feedback,’ said Marie-Claude Hemming, Policy Director at Environmental Industries Commission. ‘Getting Biodiversity Net Gain right is critical, and this added clarity on exemptions, timescales and nationally significant infrastructure project (NSIP) implementation gives EIC members the certainty they need to plan and invest with confidence. Crucially, it keeps the focus where it belongs: on delivering tangible, lasting gains for nature.’
Image: Avel Chuklanov/UnSplash
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