February 2026
As the Government prepares to consult on changes to Biodiversity Net Gain (BNG), including proposals affecting brownfield development, the policy sits at a critical juncture. What happens next will determine whether BNG matures into a credible, investable mechanism for nature recovery, or is further hollowed out by exemptions that make compliance optional in all but name.
At the end of 2025, the Government announced its intention to introduce a new area-based exemption for the smallest sites under 0.2 hectares. That decision fundamentally changes the landscape. It should now be clear that the existing impact-based ‘de minimis’ exemption is no longer needed and must be closed. Retaining both would not be refinement; it would be a clear policy regression.
The data from BNG’s first year is stark. Of the 80,400 approved planning applications for large and small domestic and commercial development, 69,500 (86%) claimed an exemption from BNG. More than half of all applications relied on the self-declaratory de minimis route. Even more concerning, around 35% of developments over 0.5 hectares, including sites spanning several hectares, claimed that their impacts on biodiversity were “minimal”. A genuinely de minimis impact on nature at that scale should be vanishingly rare. Instead, it appears suspiciously routine.
Current rules perversely make non-compliance easier than compliance. To claim de minimis, an applicant needs to only state that they believe the exemption applies at the point of submitting a planning application. No evidence, no scrutiny, no metric, no habitat plan. By contrast, complying with BNG triggers extensive mandatory assessments and documentation. This incentive structure is obviously wrong.
Linear features such as watercourses highlight the problem. Losing less than five metres of a non-priority watercourse can fall under de minimis, yet cumulatively these losses across a catchment represent a major missed opportunity for restoration. The system is leaking value at precisely the points where strategic recovery should be happening.
Any new 0.2ha exemption must fully replace de minimis, not sit alongside it. Initial analysis suggests that if both are retained, over 90% of applications could be exempt, fundamentally undermining the policy and destabilising the emerging BNG market. That outcome would be incompatible with the Government’s manifesto commitment to restore nature, and with repeated assurances to the sector that BNG was safe.
The starting point for reform must be to close the de minimis exemption itself, rather than layering new cop-outs on top of an existing loophole. Compliance must be easier than avoidance, and anyone claiming an exemption must prove they are doing so legitimately. At a minimum, this means requiring reliable evidence for all exemptions: confirmation of site size using spatial tools, metric sheets to demonstrate pre-development biodiversity value, a habitat plan, confirmation that no priority habitats are affected, and assurance that habitats have not been degraded.
Against this backdrop, suggestions of a new brownfield residential exemption are deeply concerning. Brownfield sites are central to the BNG system: 54% of new homes in 2021/22 were built on brownfield land. Far from being biodiversity deserts, many support valuable open mosaic habitats and important species. Indeed, brownfield regeneration has produced some of the UK’s flagship BNG examples, from Kidbrooke Village to Landsec’s urban regeneration portfolio and commitments, helping provide greener development and access to greenery on people’s doorsteps.
Public access to urban nature isn’t a nice to have, it is a social and ecological imperative that BNG can help achieve. Natural England’s People and Nature Survey shows that while demand for urban green space is rising, with 51% of adults visiting an urban green space between July and September 2024, provision remains woefully uneven. Some 83% of the UK population now lives in urban areas, yet 38% of people lack an accessible green space within a 15-minute walk of home, and over half (51%) have no access to a decently sized green or blue space (more than 10 hectares) within one kilometre.
These figures reflect real inequalities in access to nature that impact mental and physical health, climate resilience and community wellbeing. Natural spaces in urban areas, whether repurposed brownfield, regenerated waterways, or green corridors, can help deliver multiple public benefits far beyond statutory compliance. But they require intentional planning, incentives, and investment, and BNG is one such policy mechanism. Without it, local authorities with urban nature recovery goals face yet another hurdle.
Cumulatively, there is a risk that a brownfield exemption, plus the others, would fundamentally compromise the system by making the BNG market unviable. Support for SMEs and brownfield developers should focus on access to off-site markets and on-site delivery, not blanket exemptions.
Finally, the consultation must protect local ambition. Several councils already require 20% net gain, and many more are moving beyond the 10% minimum. Local authorities must retain the autonomy to set higher targets, stricter exemption thresholds and place-based priorities aligned with Local Nature Recovery Strategies.
BNG was designed to apply to most development to help halt and reverse biodiversity loss, not to provide an administrative escape route. The forthcoming consultation is the moment to close loopholes, restore credibility, and ensure the system truly delivers for nature and local communities at scale.
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