A database of Defra statutory biodiversity metric unit values for terrestrial habitat samples across England, with plant, butterfly and bird species data

Policies requiring biodiversity no net loss or net gain as an outcome of
environmental planning have become more prominent worldwide, catalysing
interest in biodiversity offsetting as a mechanism to compensate for
development impacts on nature. Offsets rely on credible and evidence-based
methods to quantify biodiversity losses and gains. Following the
introduction of the United Kingdom’s Environment Act in November 2021, all
new developments requiring planning permission in England are expected to
demonstrate a 10% biodiversity net gain from 2024, calculated using the
statutory biodiversity metric framework (Defra, 2023). The metric is used
to calculate both baseline and proposed post-development biodiversity
units, and is set to play an increasingly prominent role in nature
conservation nationwide. The metric has so far received limited scientific
scrutiny. This dataset comprises a database of statutory biodiversity
metric unit values for terrestrial habitat samples across England. For
each habitat sample, we present biodiversity units alongside five
long-established single-attribute proxies for biodiversity (species
richness, individual abundance, number of threatened species, mean species
range or population, mean species range or population change). Data were
compiled for species from three taxa (vascular plants, butterflies,
birds), from sites across England. The dataset includes 24 sites within
grassland, wetland, woodland and forest, sparsely vegetated land,
cropland, heathland and shrub, i.e. all terrestrial broad habitats except
urban and individual trees. Species data were reused from long-term
ecological change monitoring datasets (mostly in the public domain),
whilst biodiversity units were calculated following field visits.
Fieldwork was carried out in April-October 2022 to calculate biodiversity
units for the samples. Sites were initially assessed using metric version
3.1, which was current at the time of survey, and were subsequently
updated to the statutory metric for analysis using field notes and species
data. Species data were derived from 24 long-term ecological change
monitoring sites across the Environmental Change Network (ECN), Long Term
Monitoring Network (LTMN) and Ecological Continuity Trust (ECT), collected
between 2010 and 2020.