Biodiversity Net Gain Reform - Big news for developments on small and brownfield sites

As of 15 April 2026, the Government has confirmed major changes to how Biodiversity Net Gain (BNG) will apply to minor, medium-sized and brownfield schemes. The headline is a new 0.2 hectare area-based exemption.

This marks the most substantial recalibration of BNG since mandatory requirements came into force in February 2024. The Government expect the changes to remove BNG requirements from around half of small residential permissions. 

For many single plots, infill sites and small commercial schemes, this will mean no metric, no legal agreement (including for self-build schemes) and a far more proportionate process.

Developments exempt from BNG will continue to be subject to environmental protections through national planning policy and wider regulatory requirements so ecological appraisals, and the hierarchy of avoidance, mitigation and compensation will still apply.

Impact of Biodiversity Net Gain changes on developers

However, for developers, the BNG changes are a meaningful shift towards clarity and proportionality. For LPAs, it should free up stretched ecological capacity. This will benefit the whole BNG system by focusing resources on larger development, which has the greatest impact, and therefore the potential to deliver the greatest benefits to nature.

Defra will bring forward secondary legislation before the 2026 summer recess  with the intention of these changes coming into force before 31 July 2026 (subject to parliamentary scheduling).

Guidance will also be provided on transitional arrangements for local authorities and developers. This will cover how applications are to be treated in the interim period while changes are being implemented.

Our reaction to Biodiversity Net Gain changes

Salmon Planning + Architecture are genuinely excited about these changes because they promise a more proportionate, workable BNG system that allows everyone - developers, LPAs and consultants alike - to focus effort where it can deliver the greatest real-world benefits for nature.

If you are exploring the development potential of a site Salmon Planning  + Architecture can provide clear, expert planning advice on how these BNG changes may positively affect your position. 

With Chartered Town Planners, in-house RIBA architects, and offices in Somerset and Devon, our team is well placed to support you through the whole planning and design process. You can contact us on 01749 671500 or at info@salmonplanning.co.uk.

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