Biodiversity net gain

A biodiversity metric is used to calculate the biodiversity value of habitats in ‘biodiversity units’ as a proxy for nature for the purpose of Biodiversity Net Gain (BNG). You will need to use the metric tool if your development must meet mandatory BNG requirements.

The statutory (official) biodiversity metric is a way of measuring biodiversity value for the purposes of BNG. If your development qualifies as a small site, you can use the small sites metric (SSM). The statutory metric can calculate different types of ‘biodiversity units’ and is comprised of three modules. These are:

• Area habitat units,
• Hedgerow units,
• Watercourse units.

The statutory metric needs to be completed by a competent person – the level of competency is defined in the metric user guide . If the watercourse metric needs completing, the person completing this must be trained and accredited to conduct a river condition assessment (RCA), find out more here.

The metric can help show how development might change the biodiversity value of a site and how to design, plan and make land management decisions that better support biodiversity.

It compares proposed changes in the extent, distinctiveness, and condition of habitats of habitats on a site before and after development to determine if there is a loss or gain in biodiversity.

There are four key factors that underpin this comparison:

• habitat size
• habitat quality
• habitat location
• habitat type

See the guidance about using the biodiversity metric on GOV.UK.

View the calculation tools, guidance and other documents related to the earlier versions of the biodiversity metric published by Natural England.