Metric analysis

Does the Biodiversity Metric 3.0 measure up?

Our first Natural Capital Blog highlighted upcoming policy and legal changes as efforts to understand the services provided by the environment (ecosystem services and accounting) and use them to inform policy. This is linked to investors’ interest in environmental and social governance (ESG). To be more than a buzzword, you must be able to measure what you treasure. In the world of Environment Act 2021 of providing net biodiversity gains through the planning regime, metrics matter, not least because it will become more difficult over time.

Natural England released a new and improved ‘3.0’ version of its biodiversity measure in July 2021, to increase certainty and provide a benchmark tool for environmental law. Metric 3.0 has now had a full six months to thrive, but will it measure up?

Changes from Beta

The 3.0 metric is still a terrestrial biodiversity calculator to measure a site’s existing baseline and expected biodiversity gains and/or losses from development. The overall methodology and inputs are unchanged. The changes are technical adjustments – for example, the removal of accelerated succession (a complex mechanism for calculating the maturation of woodland habitats) and the connectivity multiplier (which was often subject to interpretation).

Metric 3.0 will smooth out variations in metric results, many of which will be welcome:

  • The incentive for advanced habit formation. The 3.0 metric proportionally reduces the time it takes to reach the target state of a habitat where it has been created or upgraded (and allows habitat difficulty multipliers to be applied once a habitat has been established). The change rewards developers for early biodiversity improvements by offering a higher weighting than if the improvements were made as part of development work. For local planning authorities keen to achieve biodiversity improvement, this change in Metric 3.0 is a significant improvement over its beta version.
  • The allowance for delaying the creation/improvement of habitats. The 3.0 metric now allows habitat creation/improvement to be delayed – for example, when there will be significant delays due to phased developments and developments that temporarily require parts of the development site for construction purposes .

The 3.0 metric therefore recognizes that habitats can be created before or after development, but encourages earlier creation.

  • The “small sites” metric has also been published along with the revised metric, which is a simplified version of the 3.0 metric for residential developments on small sites (which will now fall under the mandatory BNG requirement).
  • Like 2.0, there is a balance – if modifications have been made to modify the valuation of certain habitats, the presence of other variables in the calculations of the metric softens these major modifications.

Arbitrary rules?

For critics of 2.0, Metric 3.0 hasn’t done enough to quell the grumblings given that it still relies on land (i.e. habitat) to assess and model biodiversity – rather than actual species richness. As a result, there will always be oddities:

  • 3.0 may end up overcompensating trying to reduce the attractiveness of, for example, bramble and hazel scrub – there is a strong push towards more valuable and complex habitats, but in practice this is a habitat that can play a important role in species richness in rewilding projects
  • 3.0 favors the hedge – it now reduces the difficulty penalty for all hedge habitats. Additionally, all hedges with trees have an additional bonus over their non-treed counterparts. Therefore, the Wooded Hedge is likely to be a more popular habitat replacement choice given its value in the 3.0 metric and its relatively cost-effective creation.
  • 3.0 still does not take into account protected and locally important species. As a land-based measure, the methodology builds on existing policy and legislation to protect important sites and wildlife. Given the public’s attention to certain fauna such as bees, badgers, dormice and hedgehogs, Metric 3.0 is still no substitute for professional ecological judgement.


The 3.0 metric was launched six months ago, but the 2.0 version is still in use due to updating the analysis already undertaken using the 2.0 metric. When a project has already been evaluated using version 2.0 or is being evaluated by version 2.0, version 2.0 should always be used. Although the changes in Metric 3.0 are a refinement of an established methodology, there could be significant differences between the final metric results. Until all use of the 2.0 metric disappears, attention should be paid to the metric used, especially in cases where the habitat was created in advance!

The use of the 3.0 metric will continue to exceed the 2.0 metric during 2022, before the mandatory BNG requirement comes into force in 2023 (as the 10% continues to be used as a criterion to achieve the general objectives of the NPPF).

So what?

While Metric 3.0 fixes a number of flaws and concerns stemming from the beta, there are still grumbles that the metric doesn’t go far enough. While Metric 3.0 has not yet had enough time to become the only version in use and have an impact, DEFRA has already stated that it will consult on potential revisions to Metric 3.0 before the requirement takes effect. legal 10% BNG, so watch this space; version 4.0 may bring future surprises.