Guidance on what biodiversity net gain (BNG) is and how it affects land managers, developers, and local planning authorities.
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What is biodiversity net gain?
Biodiversity net gain (BNG) is an approach to development. It makes sure that habitats for wildlife are left in a measurably better state than they were before the development.
In England, BNG is mandatory under Schedule 7A of the Town and Country Planning Act 1990 (as inserted by Schedule 14 of the Environment Act 2021).
Developers must deliver a BNG of 10%. This means a development will result in more or better quality natural habitat than there was before development.
Find out more about BNG in:
Measuring biodiversity
For the purposes of BNG, biodiversity is measured in standardised biodiversity units.
A habitat will contain a number of biodiversity units, depending on things like its:
- size
- quality
- location
- type
Biodiversity units can be lost through development or generated through work to create and enhance habitats.
Measuring biodiversity value
When considering biodiversity value, you should consult an ecologist. They will:
- measure the biodiversity value of your existing habitat;
- advise on suitable habitat creation or enhancement for the land.
Read guidance on using the biodiversity metric.
Calculating the units
There is a statutory (official) biodiversity metric, which is a way of measuring:
- how many units a habitat contains before development;
- how many units are needed to replace the units of habitat lost and to achieve 10% BNG.
Using the statutory biodiversity metric tool
To prove you have accurately calculated the number of biodiversity units for existing habitat, or habitat enhancements to achieve BNG, you must use the calculator called the statutory biodiversity metric tool.
This tool applies the statutory biodiversity metric formula.
Who BNG rules will affect
You need to know about the new rules if you’re a:
- developer of major developments
- developer of small sites from 2 April 2024
- developer of nationally significant infrastructure projects from late November 2025
- land manager wanting to sell in the BNG market
- local planning authority (LPA)
Exempt developments
Some developments are exempt from BNG regulations.
Find out what types of development are exempt.
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