The Biodiversity Net Gain (BNG) regime, introduced under the Environment Act 2021, requires most developments in England to deliver at least a 10% increase in biodiversity value compared with the pre-development baseline. For submissions this means preparation of a baseline assessment and submission of calculations, on the required metric, to demonstrate measurable (and then monitored) net gain.
This has had significant implications for applications to which this applies – particularly smaller scale proposals with more limited space and/or viability for the purchase of credits off site. Some potentially good news, therefore, is that following consultations undertaken by Defra, a series of reforms are expected to come into force next month from 31 July 2026, subject to parliamentary approval (and scheduling). These changes are intended to reduce administrative burdens on smaller developments while maintaining overall environmental protections.
The most significant change is the introduction of a new area-based exemption for sites of 0.2 hectares or less. Developments falling within this threshold will no longer be required to demonstrate the statutory 10% biodiversity net gain (so long as no priority habitats are affected). The Government has indicated that this could remove BNG obligations from a substantial proportion of small residential schemes, although existing planning policies and environmental safeguards will continue to apply.
The current exemption, up to 25 sq./m, is so small it is not usable or helpful in the vast majority of applications in our experience. From our perspective this will help some sites, and clients, hugely. It is, however, separate to BNG requirements under the Local Plan which will still stand and require submission based upon the Council’s policy.
At the same time, the current self-build and custom-build exemption will be removed. The Government consider the new 0.2-hectare exemption a simpler and broader mechanism for relieving small-scale developments from BNG requirements. As a result, self-build projects larger than 0.2 hectares may now fall within the scope of BNG where they were previously exempt. This could, comparably, affect more rural sites which would typically want to sit within a larger development boundary than more urban proposals. Proposals potentially affected by this need, therefore, to be submitted before the reforms come into force at the end of July.
A further reform will exempt temporary developments with planning permission for five years or less from mandatory BNG. The Government’s rationale is that temporary schemes offer limited opportunities to create and maintain biodiversity enhancements over the long term, and we would agree with this on the basis of managing and monitoring BNG on a 30-year basis. It just does not work for some schemes.
Changes are also proposed to the biodiversity gain hierarchy for minor developments. Currently, developers are encouraged to prioritise on-site habitat creation and enhancement before considering off-site measures. From July 2026, off-site biodiversity gains are expected to be placed on an equal footing with on-site delivery for minor schemes, providing greater flexibility in how net gain requirements are met.
Overall, the July 2026 reforms represent a significant adjustment to the BNG framework, reducing obligations for very small and temporary developments while increasing flexibility for minor schemes and, for this reason, it may be prudent to delay some submissions to later in the summer to make use of these changes. Conversely the removal of the self-build exemption may, on some site, require proposals to be submitted sooner rather than later. The implications need to be considered on a site-by-site basis.
Applicants should review the new exemptions carefully and monitor the progress of the necessary secondary legislation before implementation, which is exactly what we are doing, as consultants, in conjunction with potentially affected sites and applicants.