Overview
Biodiversity Net Gain (BNG) has now become a key consideration in almost every residential and commercial development transaction across England. Since its implementation for larger sites from February 2024 and for small sites from April 2024, developers have been required to deliver a minimum 10% uplift in biodiversity as part of the planning process. From a development land perspective, BNG is now firmly embedded within developer appraisals and pricing assumptions.
While the core principles of BNG remain unchanged, a series of updates and proposed reforms announced across 2025 and 2026 are likely to have a significant impact on landowners, developers, as well as the viability of smaller and brownfield sites going forward
What is BNG?
BNG is an approach to development that aims to leave the natural environment in a measurably better state than before development commenced. In practical terms, developers must demonstrate at least a 10% increase in biodiversity value using the Government’s statutory biodiversity metric. This can generally be achieved through on-site habitat creation or enhancement, the purchase of off-site biodiversity units from landowners, or, as a last resort, statutory biodiversity credits. Importantly, any habitat created or enhanced as part of a BNG strategy must typically be secured and maintained for a minimum period of 30 years.
The Latest
The Government published its response to the consultation on improving the implementation of BNG for minor, medium and brownfield developments in April 2026. These changes are due to come into force before 31 July 2026.
One of the most significant proposed changes is the planned introduction of a new area-based exemption for sites of 0.2 hectares or below, provided priority habitats are not present or impacted. The Government estimates this could exempt approximately 50% of residential planning permissions from BNG requirements once implemented.
Other proposed reforms include:
- Greater flexibility for smaller developments to go off-site for biodiversity mitigation;
- Streamlining of the biodiversity metric process for minor developments;
- Further consultation regarding targeted exemptions for certain brownfield residential developments;
- Expected removal of the self-build and custom-build exemption; and
- Potential exemptions for certain temporary developments, biodiversity-led schemes and public open spaces.
Impact on Development Land Values
For greenfield sites with existing ecological value, the requirement to achieve a 10% uplift can reduce developable area and place additional pressure on viability. Developers are increasingly factoring the cost of off-site biodiversity units, the loss of developable land area, long-term management obligations, ecology consultancy costs and potential planning delays associated with biodiversity approvals into their land bids. As a result, landowners should ensure BNG implications are considered at an early stage when assessing development potential and disposal strategy.
Opportunities for Landowners
Whilst BNG presents challenges for developers, it has also created opportunities for landowners capable of delivering off-site biodiversity units.
Agricultural or underutilised land can potentially be entered into the BNG market through habitat creation and registration on the Biodiversity Gain Site Register maintained by Natural England.
This can create an additional long-term income stream, particularly where land has limited development prospects but strong ecological enhancement potential.
However, landowners should take professional planning, legal and tax advice before entering into any long-term habitat management agreements, particularly given the 30-year commitment often required.
Looking Ahead
BNG is still a relatively new part of the planning system, and further refinements are clearly expected over the coming years. However, it is already having a material impact on development appraisals, planning strategies and land transactions throughout the South West.
Understanding biodiversity constraints and opportunities at an early stage is now essential for both developers and landowners seeking to maximise value and reduce planning risk.
At Vickery Holman, our development team continues to advise landowners and developers across Cornwall and the South West on development land disposal, planning strategy and market viability in an evolving landscape.
For further advice regarding development land disposals and viability, please contact a member of our development team. Expert Development Consultancy Services in the South West – Vickery Holman
