Biodiversity net gain (BNG) has been a statutory requirement for over two years now, and for many schemes, it has been one of the trickier boxes to tick.
The default position is usually a mandatory 10% BNG on most planning permissions, with some local authorities imposing higher percentages through local plans.
New regulations, laid before parliament this week and set to come into force on 6 August 2026, confirm some of the anticipated changes to the BNG regime we have been expecting.
Ros Trotman, Partner in Thrings’ Planning and Environment team takes a look at what is changing and what schemes they will impact.
What’s changing?
Here are four key changes to be aware of:
- Exemption for the smallest sites - Developments of 0.2ha or less will no longer need to deliver mandatory BNG at all, provided they don't harm any priority habitat already on site – meaning a development should not decrease biodiversity value. This will be welcome news to those delivering smaller developments.
- Short-term land use - There's a new exemption for temporary developments – where land will be reinstated within five years. Examples include seasonal polytunnels and touring caravans or glamping sites, temporary dwellings, temporary mineral extraction accesses and construction compounds. Again, this only applies where there's no negative impact on priority habitat.
- More flexibility for minor sites - For minor developments that don't qualify for the new exemption – so anything over 0.2 hectares that still counts as "minor" – there's a change to what's known as the biodiversity gain hierarchy.
- Loss of exemptions for self and custom build - The existing exemption for self and custom build development is being scrapped with BNG obligations set to apply in the same way they do for other developments from 6 August – unless, of course, they are under 0.2ha in size.
Previously, applicants were expected to try to deliver gains onsite first, only looking offsite if that wasn't possible. Under the new rules, minor sites can go straight to offsite biodiversity units without having to demonstrate that onsite provision was ruled out first. A welcome bit of flexibility for such sites.
What does this mean?
The changes as a whole are a step in the right direction to creating a more proportionate BNG regime and striking the balance between enabling development and enhancing the environment.
The new rules only apply to planning applications submitted from 6 August 2026 onwards. Anything already submitted, or any permission already granted, stays governed by the existing BNG rules.
More exemptions in the pipeline
Further changes to BNG are expected later this year, in particular:
- Brownfield: A consultation closed in June considering whether to exempt specific brownfield residential developments from mandatory BNG requirements.
- Biodiversity-led developments: Exemptions are planned for developments where the primary objective is to conserve or enhance biodiversity.
- Community Spaces: Targeted exemptions are being considered for projects that enhance parks, playing fields, and public gardens.
Thrings’ Planning and Environment lawyers have extensive experience in navigating complex local and national planning policy legislation and has successfully supported developers and local authorities through the approval and appeal processes. To find out more and for advice on your development proposals, please do get in touch.
