What Is Biodiversity Net Gain – and How Could It Affect Your Property Plans?

If you’re thinking about extending your home, converting land, or embarking on a new development project in England, you may have come across the term Biodiversity Net Gain, or BNG. It’s become a key part of the planning system in recent years, and understanding what it means can save you time, money, and stress as you move forward with your plans.

So, what exactly is BNG? In simple terms, Biodiversity Net Gain is a legal requirement designed to ensure that any development leaves nature in a better state than before. Instead of simply avoiding harm to wildlife and habitats, developers must now deliver at least a 10% increase in biodiversity compared to the site's baseline condition. This approach aims to help reverse the decline in nature while still allowing sustainable development to go ahead.

BNG became mandatory for most major developments in February 2024, with small sites following shortly after. Whether you’re building ten houses or a single outbuilding, you’ll likely need to show how your project will meet the requirement—though there are a few exemptions, such as some householder applications and very small-scale works.

If your plans fall within the scope of BNG, the process usually starts with a biodiversity assessment carried out by a qualified ecologist. They’ll calculate the site’s existing “biodiversity units” using a standardised metric. From there, you (and your ecologist) can explore how to enhance the site through measures like planting native trees, creating wildflower meadows, installing bat or bird boxes, or improving existing habitats.

Sometimes, improvements on-site aren’t feasible—perhaps the footprint of the development takes up most of the available space. In those cases, you may be able to use off-site units or purchase statutory biodiversity credits, though these options tend to be more costly.

It’s also important to note that BNG plans must be secured for at least 30 years, meaning long-term management commitments are part of the process. Local planning authorities will expect clear evidence of how habitats will be maintained and monitored over time.

For property owners, BNG doesn’t have to be daunting. With early planning and the right ecological advice, it can be woven smoothly into your project. In fact, many people find the enhancements bring added benefits—more attractive green space, boosted pollinator activity, and even increased property value.

If you’re considering development, taking BNG into account from the start will help your plans progress more smoothly—and contribute positively to the environment at the same time.