Biodiversity Net Gain (BNG) is a UK legal requirement under the Environment Act 2021, ensuring most new developments leave habitats measurably better for wildlife, typically requiring a 10% increase in biodiversity. This came into effect in February 2024.
Before development begins, an ecologist carries out a baseline survey. This survey maps and measures all the habitats on the site, such as grassland, trees, ponds, or hedgerows.
On developments that require BNG (there are exemptions), these existing habitats, along with what the site will look like after development (including buildings, roads, and landscaped areas), are entered into a government-designed spreadsheet. This spreadsheet uses carefully calculated formulas to work out how much habitat will be lost or gained.
Any habitat loss must be fully replaced, and on top of that the developer must deliver at least an extra 10% biodiversity gain. This means the finished project should support more wildlife than the site did before development started.
Habitats can be enhanced or newly created, either:
- on the development site itself (this is the preferred option),
- elsewhere within the local planning authority, or
- outside the planning authority area.
The further away the replacement habitat is (the less favourable it is in the calculations), and the greater the area and/or quality of habitat needs to be created to replace it. All habitat creation or enhancement is paid for by the developer.
This habitat is secured for a 30-year period and must be monitored to ensure it has reached and maintained the condition it is meant to be in.
Every planning authority must publish data on the previous five years of development requiring BNG within its boundary. The first reporting period from implementation is shorter, covering from February 2024 to January 2026.
The first report for Stevenage Borough Council can be found here.