Since mandatory Biodiversity Net Gain (BNG) was introduced in 2024, developers have had to demonstrate at least a 10% improvement in biodiversity as part of the planning process. While the principle of BNG remains unchanged, new regulations introduced on 6 August 2026 have significantly altered how some developments are assessed.
The reforms exempt many smaller developments from mandatory BNG requirements, introduce greater flexibility for minor sites, and remove certain existing exemptions. For some projects, this could reduce costs and simplify planning. For others, particularly self-build developments and schemes affecting priority habitats, the requirements remain largely unchanged.
Understanding whether these changes apply to your development is now an important early-stage consideration. Getting it wrong could lead to delays, unnecessary expenditure or problems during planning determination.
In this article, our Director of Ecology, Gregor Neeve, explains what has changed, the practical implications for developers and landowners, and what these reforms may mean for the future of the BNG market.
In this article, our Director of Ecology, Gregor Neeve, will discuss the changes, the practical implications for developers, and the importance of seeking ecological guidance early in the planning process.
Gregor’s overview of the changes
These changes don’t signal a reduction in the importance of biodiversity within the planning system. Instead, they’re intended to make the process more proportionate, reducing burdens on smaller developments while allowing greater focus on schemes with the greatest potential to deliver meaningful ecological improvements. The key challenge for developers will be understanding whether they genuinely qualify for the new exemptions and how those exemptions interact with wider ecological and planning constraints.
What BNG changes have been made?
The regulations surrounding Biodiversity Net Gain (BNG) changed in England on August 6th 2026 for planning applications made on or after this date. These are the first of many updates the government is introducing this year. The following exemptions have been introduced:
0.2 hectare exemption
The change that will have the greatest impact on smaller sites is the exemption where the red line boundary (outline showing the exact land included in a planning application) is no more than 0.2 hectares. This measurement applies to the entire development rather than the built footprint alone. Therefore, access roads, land, and landscaping are all included in the measurement.
However, there is an important caveat. This exception does not apply in instances where a development will impact priority habitats, which are identified as being of critical importance for biodiversity in England. Some examples of priority habitats include lowland meadows and heathland. If your site contains a priority habitat, then standard BNG rules still apply.
While the 0.2 hectare exemption may reduce costs and planning implications, ecological due diligence remains essential to avoid incorrect exemption claims and to identify priority habitats early. Furthermore, an exemption from mandatory BNG is not an exemption from wider ecological considerations such as protected species and habitats.
Temporary development exception
A second exception applies to temporary developments where planning permission is granted for five years or less, and the land is reinstated at the end of the project. This will benefit festivals, pop-up retail vendors, temporary construction sites, and other short-term uses. Prior to this exception, the 30-year habitat obligation would apply to a development that may only be in use for three or four years.
As with the 0.2 hectares exception, the same priority habitat caveat applies. If the temporary development will negatively impact priority habitats, the standard BNG rules apply. It also does not cover phased development schemes where an individual phase may be temporary, but the overall development is permanent. Additionally, wider ecological considerations and planning permission remain factors in development. To ensure your site complies with the latest BNG regulations, we’d recommend seeking professional ecological advice and guidance during the early stages of planning.
Off-site BNG for minor developments
Perhaps the most commercially impactful change is the flexibility for minor developments to choose how they offset their BNG. Previously, developers had to attempt to offset their biodiversity onsite before moving to offsite solutions, such as habitat banks.
Under the new regulations, developers working on minor sites can choose to offset the biodiversity offsite in the early stages. This will be a welcome change for those working on minor developments who often struggle to meet the standard BNG requirements within the boundaries of their site. The requirement to maintain priority habitats remains, but minor sites now have more flexibility in how they deliver biodiversity.
Minor developments cover:
- Residential developments: Sites with between 1 and 9 dwellings covering 1 hectare of land.
- Commercial developments: Sites with floorspace less than 1,000 square meters. Alternatively, a site with a total area of less than 1 hectare.
Self-build exemption removal
Alongside the introduction of BNG exemptions, an existing exemption has been removed. The exemption for self-build developments has been removed, meaning they will be treated the same as any other development where BNG rules apply. The only caveat is if other exemptions are in place, such as the 0.2 hectare exemption. Self-build developers will need to familiarise themselves with BNG requirements to ensure the current legislation does not impede their project.
What is the impact on habitat units?
It’s reasonable to assume demand for habitat banks will vary depending on the development’s requirements.
The 0.2-hectare exception will remove these projects from the habitat bank market, as they won’t need them. However, allowing minor developments to offset BNG offsite early in development will increase demand for habitat banks. This could accelerate the market through early engagement, faster turnaround, and the ability to demonstrate the value of habitat banks to future minor development projects.
Whether the BNG changes will result in a net loss or gain for habitat banks will depend on their availability in high-demand locations, costs, and market conditions.
What remains the same?
The de minimis exemption, which excludes small development projects with trivial habitats from the 10% net gain rule, remains in place. This exemption may apply where impacts are limited to very small areas of non-priority habitat and certain threshold criteria are met. Priority habitats remain excluded from the exemption.
What changes are yet to come?
While the latest BNG conversation centres on “exemptions”, the wider story is the evolving approach to the BNG market. The August changes are the first to be introduced this year. They remind us that the BNG market is under constant evaluation; developers and habitat banks need to be agile in response to changing conditions.
The following updates are still to be introduced this year:
- November 2026: Mandatory BNG is scheduled to apply to Nationally Significant Infrastructure Projects (NSIPs), bringing major infrastructure projects such as energy, transport and water schemes within the BNG regime.
- Brownfield housing developments. Potential further reforms relating to brownfield and housing development are being considered by Government, although details and timescales have not yet been confirmed.
How can Thomson help?
Our specialist team of ecologists at Thomson Environmental Consultants have experience helping developers offset BNG on their developments. We can support you with early land assessments to help you understand whether BNG regulations apply to your development. We use this data to support strategy and planning permission applications.
With the evolving BNG market and new changes coming soon, it’s critical that developers understand what the updates mean for their projects before requesting planning permission. Addressing these issues early can help reduce the risk of redesign and project delays. Get in touch to speak with our friendly team for advice.
