Biodiversity net gain is a planning requirement in England: most development must deliver a measurable gain in biodiversity value over the pre development baseline, secured for a long period. It is measured with a statutory metric, it changes what a site is worth to develop, and it is the reason ecology now appears on schemes that would never have needed a survey before.
The BNG assessment: how the gain is measured
The site's habitats are surveyed and scored with the statutory biodiversity metric to give a baseline, the post development habitats are scored the same way, and the difference has to meet the required percentage gain, secured and maintained for the statutory period.
The hierarchy
On site gain first, then off site units, then statutory credits as a last resort. Each step costs more than the one before it, which is why the metric belongs in the design rather than at the end of it.
BNG exemptions
The regulations exempt certain categories, including householder applications and some small or self build schemes, and there are transitional cases. The exemptions are specific and are the first thing to check because they decide whether any of this applies at all.
Biodiversity net gain Wales and biodiversity net gain Scotland
The statutory English regime does not extend to Wales or Scotland, which pursue biodiversity through their own planning policy. A developer working across borders needs to know which regime the site is in before commissioning anything.
Questions people ask about BNG requirements
What are the BNG requirements?
Most development in England must deliver the required measurable gain over the pre development baseline, calculated with the statutory metric and secured for the statutory period.
What are the biodiversity net gain exemptions?
The regulations set out the exempt categories, including householder development and certain small sites, with transitional provisions. Check the current guidance for your application type.
Does BNG apply in Wales or Scotland?
The statutory English requirement does not. Both nations address biodiversity through their own planning policy, so the obligations differ.
What is the biodiversity net gain legislation?
In England the requirement comes from the Environment Act 2021 and the regulations made under it, which set the statutory metric, the required gain and the exempt categories. Wales and Scotland pursue biodiversity through their own planning policy instead.
What do the biodiversity net gain regulations require?
A measurable gain over the pre development baseline, secured for thirty years, using the statutory metric and following the hierarchy of on site first, then off site, then statutory credits as a last resort.
What does a biodiversity net gain planning condition actually require?
That the gain is delivered and maintained rather than promised. In practice the condition ties the permission to an approved biodiversity gain plan, so development cannot begin until the plan is approved, and it then requires the habitat works to be carried out and the significant on site enhancements to be maintained for thirty years with monitoring reports at stated intervals. What surprises applicants is the length of that tail and who carries it: the obligation runs with the land, secured by a planning obligation or a conservation covenant, so it becomes a matter for the title and for whoever buys the site.