Biodiversity Net Gain Changes in 2026
Biodiversity Net Gain became mandatory for most developments in England in February 2024, marking a significant shift in how the planning system accounts for nature. The landscape is moving quickly, and 2026 brings some of the most significant changes since that introduction. Here's what's happening, and what it means in practice.
The 0.2 hectare exemption
From 31 July 2026 (subject to parliamentary scheduling) all development on sites with a red-line area of 0.2 hectares or less will be exempt from mandatory BNG, unless priority habitats are affected. Defra estimates this removes approximately 50% of residential planning permissions from the BNG regime.
For SME house builders, this change is significant. For larger developers delivering schemes at scale, however, the full 10% BNG requirement remains in place. It is important to note that eligibility for the exemption depends on more than site area alone. A brief ecological appraisal before submitting a planning application can help identify any constraints at an early stage, as the presence of priority habitats may mean an exemption does not apply even where the 0.2-hectare threshold is met.
NSIPs from November 2026
On 15 April 2026, the government confirmed that BNG will become mandatory for all Nationally Significant Infrastructure Projects from 2 November 2026, applying a consistent 10% BNG requirement across all NSIP types.
Given the scale of many NSIP schemes, they are expected to increase demand for off-site biodiversity units in some areas. Developers bringing forward projects in locations where NSIPs are planned may benefit from considering off-site BNG requirements at an early stage.
Across Sussex, Kent and Hampshire where a number of energy infrastructure projects are progressing through the planning system, increased competition for off-site units could influence availability and pricing over time.
What this means
For developers, the key considerations are understanding whether exemptions apply and planning ahead for any off-site BNG requirements. If you're bringing forward residential schemes above 0.2 hectares - which most volume house builder sites will be - your ecological obligations remain unchanged.
What is changing is the competitive landscape for off-site units, and the complexity of navigating exemptions that come with their own conditions and caveats.
Navigating these changes requires ecological input early - before planning submission and ideally before site selection. The Ecology Co-op works with house builders across the South East of England at every stage of that process, from preliminary appraisal through to habitat management and monitoring.