ECT awarded Cicely Marshall (University of Cambridge) a Small Grant for work at multiple LTEs on our national register. This grant contributed to her work on calculating biodiversity units at ECT sites using Natural England’s Biodiversity Metric 3.0 which was launched in July 2021. Cicely shares the results of her publication here.
In England, it is now a legal requirement of the planning process that developers leave nature in a better state than they found it. Developers must demonstrate how a project will achieve a biodiversity net gain of at least 10% quantified using a new Defra tool called the Statutory Biodiversity Metric. The metric uses habitats as a proxy for total biodiversity, scoring habitats’ intrinsic distinctiveness and current condition using field observations.
The UK is committed to building 300,000 homes a year by mid-2020. The net biodiversity gain requirement is therefore expected to generate a market for biodiversity credits worth an estimated £135M-£274M annually, substantially increasing funding for nature conservation in England.
With a small grant from the Ecological Continuity Trust awarded in 2022, we carried out an England-wide validation study of the metric. We calculated biodiversity units using the statutory metric during field visits to 24 long-term monitoring sites. We correlated those biodiversity units against plant, bird and butterfly species data already held by the sites. We found that the metric captured plant biodiversity reasonably well. But we found no relationship between biodiversity units and any of the indicators we calculated for birds nor butterflies.
This means there is no evidence that a 10% net biodiversity gain calculated using the statutory biodiversity metric will translate into real-life gains for birds and butterflies without additional conservation management.
Long-term experiments such as the Palace Leas meadow hay plots at Cockle Park, Northumberland are useful for studying different grassland habitat types in close proximity. Photo credit Cicely Marshall
This is the first comprehensive study of the performance of Defra’s statutory biodiversity metric across England. The results have been published in the Journal of Applied Ecology (Marshall et al., 2024). We have met with Natural England and Defra to discuss our results and recommendations, which will feed into a work programme over the coming years to enhance the metric’s performance.
Plants, birds and butterflies have been surveyed comprehensively in England over many years, and are used as indicators for the national state of nature. Being able to reuse species data from long-term monitoring sites proved essential to the work. We were able to publish much more quickly than collecting species data from scratch, which is important for policy-relevant research. We were also able to account for the natural annual variation in bird and butterfly populations, which would otherwise have been cost-prohibitive to include.
Undergraduate students Isla Kendall and Kristian Wade carrying out condition scoring at Alice Holt woods, a long-term monitoring site within the Environmental Change Network. Photo credit Cicely Marshall
We worked at sites supported by the Ecological Continuity Trust, including those at Park Grass and Palace Leas, as well as those associated with the UK Environmental Change Network (UKECN) and England’s Long Term Monitoring Network.
Additional Reference
Marshall, C., Wade, K., Kendall, I., Peacock, S., Simkin, J., Bladon, A., Porcher, H., Poffley, J., Treweek, J., & Marrs, R. (2024). Data from: A database of Defra statutory biodiversity metric unit values for terrestrial habitat samples across England, with plant, butterfly and bird species data. Dryad Digital Repository [Available online at: https://doi.org/10.5061/dryad.n5tb2rc0k]
