In the context of decades of biodiversity loss, habitat degradation, and pollution, Biodiversity Net Gain (BNG) offers a glimmer of hope – that the rapid ecological decline can be reversed, by recognising the value of nature and incentivising (and obligating) the creation and connection of good condition habitats across the country. 

Since BNG became mandatory in 2024, local planning authorities (LPAs), developers, ecologists and other industry professionals have had to quickly adapt to the new legislative requirements, and the additional workload this has generated. At Stroud District Council a dedicated ‘BNG Officer’ post was created – a role I was appointed to in January 2025.      

Key challenges of early implementation 

The BNG is a world-leading policy, and whilst the legislation creates a robust framework, as with any new policy, the first years of implementation have thrown up challenges, and highlighted areas for potential improvement. Some of the main challenges I have encountered have been:

• Ambiguous guidance – while Government guidance on BNG is often highly prescriptive, in some circumstances, it is somewhat ambiguous. For example, determining what constitutes a ‘significant on-site gain’. Current guidance is loosely worded and could be interpreted to require almost all development - including small sites delivering minor enhancements such as planting a couple of trees - to be secured through a 30-year Habitat Management and Monitoring Plan (HMMP). This could place a substantial and ever-increasing administrative burden on the LPAs, as well as disproportionate costs on development, for relatively limited ecological benefit. In the absence of nationally agreed thresholds, LPAs are relying on professional judgement, leading to inconsistencies in application.
• Legislative loopholes – there are a few loopholes that could potentially be exploited by developers wishing to avoid BNG requirements. For example, the exemption for self-build and custom build development of up to 9 houses on sites under 0.5 hectares can be claimed, though there is no reliable mechanism to enforce this and stop these houses being sold on the open market. Similarly, the inability to apply pre‑commencement BNG conditions to retrospective and part‑retrospective applications creates a significant loophole. If a development has already begun at the point of applying for permission, BNG requirements can effectively be bypassed, which incentivises poor practice.
• Disproportionate burden on very small sites - The level of effort required to bring some small applications (e.g. sites under 1,000m²) to an acceptable standard can be disproportionate. These schemes often require multiple rounds of consultation and revision despite delivering relatively straightforward ecological enhancements, such as tree planting or wildflower seeding. 

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The Future of BNG

The Government carried out a series of consultations last year aimed at improving and simplifying the legislation, and the responses to these consultations were published last month.

Of the more than 25,000 responses received, the vast majority opposed the introduction of additional BNG exemptions, a position campaigned for by the RSPB and the Wildlife Trusts. Among the remaining respondents, there was broad support for introducing targeted exemptions, particularly for development on sites under 0.1 hectares and for proposals whose primary purpose is to conserve or enhance biodiversity.

Following its analysis of all the responses, the government is proposing the following changes to the BNG legislation:

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Phase 1 (expected late July 2026)

🏡 Development on sites under 0.2 hectares will be exempt - provided that no priority habitats are impacted.

🏕️ Temoporary permissions granted for a maximum of five years will be exempt – provided that the entire development is temporary, and no priority habitats are affected.

🏠 Self-build and custom-build exemption to be removed – however most of these will be covered under the 0.2 exemption.

▼ Biodiversity gain hierarchy for minor development amended – to give off-site BNG delivery equal priority to onsite habitat creation and enhancement.

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Nationally significant infrastructure projects

🚝 BNG will apply to all NSIP applications submitted on or after 2 November 2026.

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Phase 2 (expected early 2027)

Exemptions

🌿 Development whose primary purpose is biodiversity conservation or enhancement will be exempt - e.g. habitat creation requiring planning permission or ponds delivered under district-level licensing. 

⛲️ Development that enhances parks, playing fields and public gardens (Professional sports stadia will be excluded).

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Potential exemptions

🏭 Brownfield residential development – a consultation on the definition of brownfield residential development, potential thresholds for an exemption, and measures to ensure negative ecological impacts are avoided is open until 10^th June 2026.

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Changes to the biodiversity metric 

🌐 Biodiversity metric to become digital (web-based platform) - with potential use of automated GIS baselining to be explored for simple sites.

🗺️ Spatial risk multiplier to be based on Local Nature Recovery Strategy (LNRS) areas rather than LPA boundaries

❇️Rule 4 (trading rule flexibility) to be reviewed to better support strategic biodiversity creation linked to major capital infrastructure projects

🌊Watercourse module to be simplified, including exploration of a new category for ‘heavily modified watercourses’

🟩 de minimis exemption - retained for now with existing thresholds but could be subject to review following the brownfield residential consultation.

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The implications of BNG amendments 

The proposed changes are expected to substantially reduce the number of small schemes requiring BNG. This should alleviate the disproportionate financial and administrative burden placed on applicants and LPAs alike, allowing resources to be focused on larger schemes with greater potential to deliver meaningful nature recovery. 

However, the decision to exempt all sites under 0.2 hectares remains contentious. This threshold is double that advocated for by the Chartered Institute of Ecology and Environmental Management (CIEEM) and is concerning as even small sites can play an important role in limiting biodiversity decline and supporting habitat connectivity, particularly in urban environments. 

That said, it is reassuring that a blanket exemption for all minor development (fewer than 10 homes on less than 0.5 hectares) was rejected, as this would have significantly reduced the effectiveness of the legislation and negatively impacted the emerging off-site BNG market.

The elephant in the room, however, is the continued failure to address the loophole relating to retrospective development. This undermines the credibility of the regime, risks incentivising poor practice, and creates an uneven playing field for applicants who engage with BNG properly at the pre‑application stage. Similarly, without precise drafting and robust guidance, some of the new exemptions could also be vulnerable to exploitation.

In conclusion, although the cumulative effect of multiple new exemptions will slightly reduce the effectiveness of BNG legislation, I am optimistic that overall, BNG will continue to make a meaningful contribution to nature recovery. BNG remains a bold and world‑leading approach—but its credibility will depend on whether its safeguards are strengthened and not gradually eroded.

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Joel Hunziker 

The opinions expressed in this blog are solely my own and do not express the views or opinions of Stroud District Council.