Biodiversity units explained
Biodiversity units serve as the standard ecological "currency" used to measure the natural value of land in England. Under current Biodiversity Net Gain (BNG) regulations, nearly all new developments must deliver at least a 10% increase in biodiversity value to secure planning permission.
As the expert consultancy arm of the Derbyshire Wildlife Trust, Wild BNG is here to guide developers, planners, and architects through the complexities of the unit system. We ensure your project unlocks high-integrity, local solutions that satisfy planning requirements while directly supporting Derbyshire's nature recovery.
How Biodiversity Units Are Calculated
Biodiversity units quantify the natural habitat before a development begins (the baseline) and compare it against the projected habitat value after construction is complete. This calculation is carried out by a qualified ecologist using Natural England's Statutory Biodiversity Metric.
The metric converts real-world habitat data into a measurable unit score based on four core pillars:
- Habitat Size: Measured in hectares for area-based habitats, or meters for linear features like hedgerows and watercourses.
- Distinctiveness: How rare, ecologically valuable, or difficult to replace a specific habitat type is.
- Condition: An assessment of how healthy, diverse, and well-functioning the habitat is (ranging from poor to good).
- Strategic Significance: Whether the land aligns with local conservation priorities, specifically the Derbyshire Local Nature Recovery Strategy (LNRS).
The net units required for your project are the difference between your baseline value and your post-development target, including the mandatory 10% uplift.
The three distinct unit types
The Statutory Metric does not calculate a single, catch-all score. Instead, it measures nature across three completely separate categories of units, representing different ecological systems:
The three distinct unit types
The Statutory Metric does not calculate a single, catch-all score. Instead, it measures nature across three completely separate categories of units, representing different ecological systems:
Habitat Units
Applied to standard, land-based areas such as grasslands, woodlands, and wetlands.
Hedgerow Units
Applied to linear boundary features such as hedges, treelines, and field borders.
Watercourse Units
Applied to linear aquatic features such as rivers, brooks, and streams.
Because these modules operate independently, units cannot be mixed, combined, or traded against one another. Your project must balance its ecological accounts for each individual unit type that occurs within your site footprint. A surplus in habitat units can never be used to offset a deficit in hedgerows or watercourses.
