Biodiversity units
Biodiversity units are calculated values used by a specified biodiversity metric to represent habitat value before and after an intervention. In England's statutory approach, calculations combine habitat area or length with factors such as type, condition, distinctiveness, location, difficulty, time, and spatial risk under defined metric rules.
In simple terms
A biodiversity unit is not a universal physical unit like a kilogram. It is an output of a particular method. In England's statutory metric, a competent assessment records habitats and applies prescribed factors to establish baseline, losses, gains, and delivery requirements. Habitat categories are calculated in the relevant modules, and units from different habitat types cannot always be treated as interchangeable. Because the result depends on field evidence, condition assessment, location, timing, and the metric version, a unit figure should always identify its method, date, assumptions, and habitat basis.
Why it matters
Units give planning decisions a structured way to compare a site's biodiversity baseline with proposed outcomes and to account for delivery risk. They support biodiversity net gain calculations, but do not capture every species, ecological function, or local value. The mitigation hierarchy and legal protections still apply; a positive number is not permission to damage irreplaceable habitat.
Example
A development team surveys on-site habitats, records their areas and condition, and calculates baseline units using the current statutory metric. It then models retained habitat, creation, and enhancement, including time and difficulty multipliers. The team reports each habitat module separately and documents who completed the assessment and which metric files were used.
How it differs
Biodiversity net gain
Biodiversity units are method-specific calculated values; biodiversity net gain is an outcome or requirement assessed by comparing relevant pre-development and post-development biodiversity values under applicable rules.
References
Current status
- As of
- Issuer
- Department for Environment, Food & Rural Affairs
- Jurisdiction
- England
- Instrument or version
- Statutory biodiversity metric
- Status
- The statutory biodiversity metric and supporting calculation resources are published for use in England; calculations depend on the applicable metric version and its rules.
Applicability: This entry explains biodiversity units through England's statutory metric. The result is method- and jurisdiction-specific, so users should confirm the current metric, exemptions, transition rules, and competent professional requirements for a particular project.