Published15 April 2025Updated9 July 2026
Biodiversity Net Gain: A Quick Guide for Anyone Who Isn't an Ecologist
New developments in England now have to leave nature better off than they found it, by law. Here's what Biodiversity Net Gain requires, in plain English.
Biodiversity Net Gain is now a legal requirement on most new developments in England. Here's what it means, without the ecology degree.
Biodiversity Net Gain, BNG to anyone who has to deal with it more than once, is a planning requirement under the Environment Act 2021. In plain terms: if you build something, you now have to leave nature measurably better off than it was before you started. Not the same. Better.
The headline number: 10%
Most developments now have to deliver a minimum 10% net gain in biodiversity value compared with what was on site beforehand. That gain is measured using Natural England's biodiversity metric, which scores habitats on type, size, condition and location rather than on how nice they look from the road.
Who has to do this
BNG became mandatory for most major developments first, with smaller sites brought in a couple of months later. Householder applications are exempt, and there's a de minimis threshold for genuinely small-impact schemes, so not every extension needs a biodiversity metric calculation attached to the application.
Three ways to hit the number
On-site is the preferred route: build the habitat gain into the scheme itself, hedgerows, ponds, planting, roosting space, whatever the metric rewards on that particular plot. Where on-site gain isn't achievable, off-site habitat can be secured elsewhere, often through a habitat bank or a land management agreement. As a last resort, developers can buy statutory biodiversity credits from the government, priced deliberately high enough that nobody treats it as the easy option.
The 30-year catch
Whatever habitat gets delivered has to be maintained and monitored for a minimum of 30 years, secured through a legal agreement tied to the land. This isn't a one-off planting scheme for the opening photos. It's a long-term commitment that needs planning for from day one, not bolted on after the landscaping drawings are finished.
What this means at the application stage
A Biodiversity Gain Plan has to be submitted and approved before development begins, which means the ecology survey and the metric calculation need to happen early, not the week before submission. Leave it late and you're either redesigning the scheme around a habitat requirement you didn't plan for, or waiting on a survey that has its own season to work in. Bats and newts do not care about your programme.
Areas We Cover
JSA Architects Across the Midlands
We work with homeowners, developers, and landlords across the Midlands. Fees, planning authorities, and project types vary by location — find local insight and project examples for your area:
Architects in Derby → — Quarndon, Kirk Langley, Duffield, Allestree, Darley Abbey, Mickleover, Littleover
Architects in Nottingham → — The Park Estate, West Bridgford, Edwalton, Mapperley Park, Wollaton, Bramcote
Architects in Lichfield → — Shenstone, Little Aston, Four Oaks, Streetly, Aldridge, Walsall, Tamworth, Whittington
Architects in Solihull → — Knowle, Dorridge, Hampton in Arden, Shirley, Dickens Heath, Olton
Architects in Sutton Coldfield → — Four Oaks, Wylde Green, Boldmere, Mere Green, Streetly, Little Aston
faq's
Common Questions
A legal requirement under the Environment Act 2021 for most new developments in England to leave biodiversity at least 10% better than it was before the development, measured using Natural England's biodiversity metric.
No. Householder applications are exempt, along with developments that fall under the de minimis threshold for minimal habitat impact.
A minimum of 30 years, secured through a legal agreement.
Developers can secure off-site habitat, often through a habitat bank, or as a last resort purchase statutory biodiversity credits from the government.
As early as possible. A Biodiversity Gain Plan must be approved before development begins, and ecology surveys are often season-dependent.
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