The Biodiversity Metric 4.0

The Biodiversity Metric is a spreadsheet tool and associated guidance that can be used to assess the biodiversity outcomes of a land-use change intervention. From February 2024 it will be mandatory to use the Biodiversity Metric to assess planning applications in England. It will be used to determine whether any compensation (‘biodiversity offsetting’) is required, in response to the loss or damage of pre-existing habitats on the development site, in order to deliver Biodiversity Net Gain (BNG). The Metric could also be used to assess the outcomes of NbS interventions.

It is widely expected that BNG will provide funding that could be used for nature recovery and NbS projects, although it is important to remember that BNG is mainly a compensation for habitat loss, with only a small amount of actual potential gain: the statutory minimum is 10% but this is within the bounds of uncertainty associated with use of the metric. Also, the metric itself is an imperfect representation of the actual biodiversity value of different habitats, due to its inherent simplifications.

It is vital that the BNG Good Practice Principles referenced in the Metric documentation are followed when designing and implementing Biodiversity Net Gain projects. In particular, the mitigation hierarchy must always be followed: loss of biodiversity must be avoided wherever possible, then reduced (mitigated) as far as possible, and compensation (‘offsetting’) of losses with new habitat created elsewhere should take place only as a last resort. Irreplaceable habitats may not be compensated through BNG, but if they are lost they must have a bespoke compensatory package. There is now a British Standard for Biodiversity Net Gain (BS 8683:2021, Process for designing and implementing Biodiversity Net Gain), which builds on the Good Practice Principles.