Measuring biodiversity

For the purposes of BNG, biodiversity is measured in a standardised way using the statutory biodiversity metric tool.

The metric calculates the biodiversity value of habitats in “biodiversity units”. The number of biodiversity units a habitat contains depends on different factors:

• the size of the habitat
• the habitat’s type (distinctiveness)
• the habitat’s quality (condition)
• the habitat’s location (strategic significance)

The metric measures how a development changes a site’s biodiversity value by calculating:

• the number of biodiversity units the site’s habitats (within the red line boundary) contain before development - the baseline biodiversity value
• the number of biodiversity units that are needed to replace units of habitats that are lost - and to achieve, as a minimum, 10% BNG by creating or enhancing habitats

View more information about the statutory biodiversity metric tool.

Assessment of strategic significance forms part of the calculation of on-site and off-site habitats’ biodiversity value using the statutory biodiversity metric.

Download the interim guidance on strategic significance

This interim guidance will remain in place until the Local Nature Recovery Strategy (LNRS) for the West Midlands, produced by West Midlands Combined Authority, is formally published. The LNRS is due to be published during 2025.

Page last updated: 23 December 2024