The government has confirmed its intention to introduce a new area-based exemption from mandatory Biodiversity Net Gain (BNG) requirements for certain small development sites in England. Under the proposed changes, development on sites of 0.2 hectares or less will be exempt from the statutory BNG regime, provided no onsite priority habitat is affected. The reform is expected to be implemented through secondary legislation, with a target date before 31 July 2026, subject to parliamentary approval. 

What’s changed? 

At present, BNG applies to most developments unless a specific exemption is met. Existing exemptions are limited, including the ‘de minimis threshold’, which applies where development does not affect priority habitat and impacts less than 25 square metres of habitat or 5 metres of linear features such as hedgerows. In practice, many small sites, such as infill plots and minor residential schemes, still fall within the scope of BNG. This often requires developers to engage ecological consultants, apply the statutory biodiversity metric, and in some cases secure off-site biodiversity units or statutory credits where onsite provision is not achievable. 

The proposed reform represents a shift away from this impact-based approach by introducing a clearer, area-based threshold. The 0.2-hectare limit will be assessed using the entire red-line boundary of the application site rather than the development footprint. Where a site qualifies, it will not be subject to the statutory biodiversity gain condition. This removes the requirement to demonstrate a 10% biodiversity net gain, submit a biodiversity gain plan, or use the statutory metric. 

However, the exemption will not apply where priority habitats are present and affected. In such cases, the full BNG requirements will continue to apply, meaning some small sites will still need to comply with the existing regime. 

When will the new exemption apply? 

It’s important to note that the exemption is not yet in force. Until the necessary legislation is enacted, the current BNG framework remains fully applicable. Developers should therefore be cautious about relying on the proposed changes, particularly for applications being prepared or submitted in the near future. The timing of an application will be a key factor in determining whether the current or future regime applies. 

Even once introduced, the exemption will not remove the need to consider biodiversity as part of the planning process. Local Planning Authorities will continue to assess ecological impacts in line with national and local policy and may still require proportionate supporting information. Protections for irreplaceable habitats remain unchanged, and other controls, such as Tree Preservation Orders and conservation area restrictions, will still apply. Proposals that result in unacceptable environmental harm may still be refused. 

What are the implications? 

For developers and landowners, particularly those promoting small-scale schemes such as infill housing or brownfield redevelopment, the proposed changes could reduce costs, simplify the planning process, and improve viability. However, whether the exemption applies will depend on site-specific factors, including site size, habitat constraints, and application timing. 

Early professional advice remains essential to assess eligibility and determine the most appropriate planning strategy. If you would like advice on the new BNG exemption and how your development proposals may be affected, our expert team can help. Please get in touch with us by telephone: 01789 387880 or by email: planning@sheldonbosleyknight.co.uk.