A globally influential area-condition metric is a poor proxy for invertebrate biodiversity

There is increasing demand for standardised, easy-to-use metrics to assess
progress towards achieving biodiversity targets and the effectiveness of
ecological compensation schemes. Biodiversity metrics based on combining
habitat area and habitat condition scores are proliferating rapidly, but
there is limited evidence on how they relate to ecological outcomes. Here,
we test the relationship between the statutory biodiversity metric used
for Biodiversity Net Gain (BNG) in England — and as the basis for new
biodiversity credit systems around the world — and invertebrate richness,
abundance, and community composition. We find that the combined
area-condition BNG metric does not capture the value of arable farmland
and grassland sites for invertebrate biodiversity: invertebrate
communities were highly variable across sites that had the same type and
condition under the BNG metric. We found no reliable relationship between
scores under the metric and either invertebrate abundance or species
richness, with the risk of the metric undervaluing sites of high
invertebrate value. Our results highlight the need to incorporate factors
beyond habitat type and condition into site evaluations, and to complement
metric use with species-based surveys. This dataset contains the
invertebrate abundance and richness data collected and used in the
analysis of this paper.