Phil Gregory, commercial property partner at Square One Law, discusses the changes to biodiversity net gain and how this fits into the development landscape
Biodiversity net gain (BNG) became mandatory for Nationally Significant Infrastructure Projects (NSIPs) on 2 November 2026, meaning developers applying for a development consent order (DCO) must now demonstrate how their project will deliver at least a 10% net gain in biodiversity.
NSIPs are categorised as large-scale development projects which are considered vital to the country’s economic or social needs. These could be major road projects, wind farms or power stations, for example. Because these are major projects, the implications of providing BNG could be significant.
BNG has been part of the development landscape for some time, so developers will already be familiar with the need to factor it into any plans, but its extension to NSIPs brings additional considerations, particularly around land, costs and long-term responsibilities and reaffirms the message that requirements for BNG on development are here to stay. The extension to nationally significant infrastructure projects builds on those existing requirements, with many of the same commercial considerations applying.
For most of our clients at Square One Law, the focus remains on making BNG work in practice. It’s about understanding the land and cost implications, securing any off-site biodiversity units, and agreeing who will deliver and maintain the habitat improvements.
Those arrangements need to hold up throughout the life of the commitments, including when designs change, construction finishes or land changes hands. Clear agreements at the outset help avoid uncertainty, delays or disputes further down the line.
The recent exemption for sites of 0.2 hectares or below, subject to conditions including protection for priority habitat, also means developers should check the position for each scheme. The requirements continue to evolve, but early planning and clear responsibility remain central to getting BNG right.
What the BNG changes mean for Nationally Significant Infrastructure Projects (and a reminder of how it continues to apply to all relevant development)
The new requirements have been introduced through Schedule 15 of the Environment Act 2021, which inserts Schedule 2A into the Planning Act 2008.
This means developers of NSIPs must use the government’s statutory biodiversity metric to calculate the site’s existing biodiversity value and demonstrate how the project will achieve the required 10% increase.
A single metric calculation is required for the whole development, including projects delivered in phases or across different local authority areas.
How to achieve BNG
Three ways to achieve BNG are creating or enhancing habitats on-site, purchasing off-site biodiversity units, or buying statutory biodiversity credits as a last resort.
Measuring biodiversity
BNG value is measured in standardised biodiversity units, with a habitat containing a number of units depending on factors such as size, condition, location and type.
To calculate the number of biodiversity units your development would need to achieve the required BNG, you can use the statutory biodiversity metric tool published by the government.
Exceeding BNG requirements
If your development creates more habitats or value than initially expected and achieves a biodiversity net gain in excess of the required 10%, the benefits are significant.
Not only would your development leave a smaller carbon footprint, but you could also carry the excess gains over to future developments or sell them to another development on the off-site BNG market.
If you were to sell or allocate the gains to another development, however, it is worth remembering that it is a separate process from your DCO application; therefore, the best advice to ensure you do it by the book is to follow the government’s official guidance for land managers.
Should you wish to keep the excess gains for your development, then the best course of action is to refer to the relevant national policy statements (NPS) or discuss with the planning inspectorate before submitting your DCO application.
Approaching BNG going forward
Looking ahead, it would be wise for developers to start thinking about BNG as early as possible when planning a major infrastructure project (just like any other development project), as understanding the existing biodiversity value of the land, identifying potential habitat losses and exploring opportunities for habitat improvements will be essential to getting such projects off the ground.
There are also significant commercial and legal considerations. Developers need to account for the cost of habitat creation and off-site units, as well as agreeing on who will be responsible for delivering and maintaining improvements.
Significant on-site gains can also be legally secured and maintained for at least 30 years, making it particularly important to establish clear responsibilities from the outset, including what happens if project designs change or land ownership transfers.
Planning ahead is key
As part of a DCO application, developers must submit an outline biodiversity gain plan explaining how they intend to meet the 10% requirement, alongside draft DCO requirements relating to BNG.
Our recommendation is for developers to engage with ecologists, landowners, the planning inspectorate, and relevant local authorities early to identify potential issues and reduce the risk of delays.
Ultimately, getting BNG right is about early planning, understanding the commercial implications and putting clear legal arrangements in place. Treating it as part of the overall project strategy, rather than something to address later, will help developers meet their obligations and avoid unnecessary challenges and uncertainty further down the line.
