Biodiversity Net Gain: Changes for 2026
Executive Summary
Combined with announcements made by the government in December and the forthcoming revisions to the National Planning Policy Framework (NPPF), our assessment is that Biodiversity Net Gain (BNG) is neither being strengthened nor weakened.
Instead, the government appears focused on addressing early implementation issues, reducing complexity for Local Planning Authorities, and removing barriers for SME and brownfield development. At the same time, BNG is being steadily introduced to Nationally Significant Infrastructure Projects (NSIPs), with the intention of creating a smoother and more consistent, “one-size-fits-all” approach across the planning system.
Overall, the direction of travel is towards simplification, flexibility for smaller schemes, and earlier, more strategic consideration of biodiversity impacts for large-scale development.
What Does This Mean for Developers?
For smaller developments, particularly minor and brownfield sites, the proposed changes reduce regulatory burden and introduce greater flexibility. Planning and delivery should become more straightforward, with improved access to offsite Biodiversity Net Gain units and fewer procedural hurdles.
For larger developments and major infrastructure projects, BNG becomes more strategically important with Temporary Permission exemption expansion from 2 to 5 years indicating a more pragmatic approach for infrastructure and enabling works. Nationally Significant Infrastructure Projects will need to consider biodiversity impacts much earlier in the project lifecycle, with increased demand and competition anticipated within the offsite BNG unit market.
In summary:
Less burden on small sites, with more strategic planning required for major developments.
Key Policy Changes – Detail
Confirmed changes expected to be in place by 31 July 2026
• A general exemption from BNG for sites with a red-line boundary of 0.2 hectares or less.
• A general exemption from BNG for temporary developments with a duration of up to five years.
• Removal of the existing self-build and custom build exemption.
• Disapplication of the biodiversity gain hierarchy for minor development, placing offsite gains on an equal footing with onsite habitat enhancement and creation.
Nationally Significant Infrastructure Projects (NSIPs)
BNG will apply to NSIPs from 2 November 2026 (pushed back from May 2026). The NSIP BNG regime will be more front-loaded than the existing system, encouraging biodiversity impacts and mitigation to be addressed during the pre-application stage.
Given the scale of NSIPs and a more relaxed approach to spatial risk, it is expected that a significant proportion of the offsite BNG unit market will be absorbed by major infrastructure projects.
Further proposals announced (subject to consultation later in 2026)
• A potential brownfield housing exemption, consulted up to 2.5 hectares (likely to be lower in practice, circa 1.5ha).
• Exemptions for developments whose primary objective is to conserve or enhance biodiversity.
• Exemptions for development that enhances parks, playing fields and public gardens.
• Reform of the spatial risk system, allowing biodiversity units to be sourced from a much wider geographic area.
• Changes to the de minimis exemption threshold where application of BNG is disproportionate to the benefits achieved.
• Introduction of a new medium-distinctiveness brownfield habitat, reducing reliance on high-distinctiveness Open Mosaic Habitat (OMH).
• Allowing alternative habitat delivery as compensation for loss of OMH.
• Replacement of the biodiversity metric with an online, map-based tool.