What is the meaning of Biodiversity Net Gain (BNG)?

Imagine a meadow brimming with wildflowers, bees humming between blossoms. If a new development is planned there, BNG ensures that the habitat is not only replaced but improved elsewhere—perhaps through rewilding a nearby plot, planting new woodlands, or restoring wetlands. This approach ensures that while development continues, the natural world flourishes alongside it.

BNG is measured using a biodiversity metric, a tool that quantifies habitat quality before and after construction. Developers must demonstrate, through careful planning, that their projects will result in a net gain rather than a net loss. The aim is not just to offset harm but to actively contribute to the health of the environment.

What Are the BNG Requirements?

BNG is not an afterthought—it must be planned from the beginning. Under the Environment Act 2021, most developments in England must adhere to these key requirements:

A clear strategy submitted at the planning stage. Developers must provide a BNG plan detailing how they will meet the 10% gain requirement.

A biodiversity assessment before development begins. Every project starts with a calculation of the site’s existing biodiversity value.

A mandatory 10% net gain. This can be achieved by enhancing nature on-site or by investing in off-site projects to compensate for any loss.

A long-term commitment. Any biodiversity improvements must be maintained for at least 30 years, ensuring sustainability beyond a project’s completion.

Which Developments Are Exempt from BNG?

Despite its broad scope, some developments are exempt from BNG requirements. These include:

• Householder applications. Small-scale home improvements like loft conversions or extensions are not required to deliver a biodiversity net gain.
• Minor developments affecting less than 25 square metres of habitat. Small-scale changes that cause minimal biodiversity impact fall outside BNG regulations.
• Self-build and custom-build homes (subject to size limits). Smaller, individually built homes on plots under 0.5 hectares are exempt.
• Change of use applications. If no physical development is taking place, BNG is not required.
• Nationally significant infrastructure projects (NSIPs). Large-scale infrastructure schemes are encouraged to consider biodiversity, but they are not legally bound by BNG.
• Marine developments. Since BNG applies primarily to terrestrial and freshwater environments, projects in the marine sector are currently outside its scope.
• Biodiversity gain sites. If a site is already being developed to enhance biodiversity as part of another project, it does not need to meet BNG rules again.
• High-speed rail transport networks. Some major transport projects, including parts of HS2, are exempt from the mandatory BNG requirement.

For a full list of exemptions and official guidance, refer to the latest government regulations on BNG compliance.

Why Does BNG Matter?

For centuries, human development has fragmented landscapes, pushed species to the brink, and degraded natural habitats. BNG represents a shift away from that trajectory. It is not just about minimising damage—it is about actively improving the land we build upon.

Imagine a future where every new housing estate includes pollinator-friendly meadows, every restored brownfield site teems with life, and every urban park is a haven for biodiversity. With BNG, this vision becomes possible.

As England implements these policies, success will depend on rigorous enforcement, creative ecological solutions, and a collective commitment to reversing biodiversity loss. The challenge is great, but so is the opportunity—to build a future where progress and nature thrive together.

Want to implement BNG in your project? Contact us today for expert guidance on sustainable development strategies and compliance with BNG regulations.