Regional Biomes outperform broader spatial units in capturing biodiversity responses to land-use change

Biogeographic context, such as biome type, has a critical influence on
ecological resilience, as climatic and environmental conditions impact how
communities respond to anthropogenic threats. For example, land-use change
causes a greater loss of biodiversity in tropical biomes compared to
temperate biomes. Furthermore, the nature of threats impacting ecosystems
varies geographically. Therefore, monitoring the state of biodiversity at
a high spatial resolution is crucial to capture variation in
threat-responses caused by biogeographical context. However such
fine-scale ecological data collection could be prohibitively resource
intensive. In this study, we aim to find the spatial scale that could best
capture variation in community-level threat responses whilst keeping data
collection requirements feasible. Using a database of biodiversity records
with extensive global coverage, we modelled species richness and total
abundance (the responses) across land-use types (reflecting threats),
considering three different spatial scales: biomes, biogeographical
realms, and regional biomes (the interaction between realm and biome). We
then modelled data from three highly sampled biomes to ask how responses
to threat differ between regional biomes and taxonomic group. We found
strong support for regional biomes in explaining variation in species
richness and total abundance compared to biomes or realms alone. Our biome
case studies demonstrate that there is variation in magnitude and
direction of threat responses across both regional biomes and taxonomic
group, although the interpretation is limited by sampling bias in the
literature. All groups in tropical forest showed a consistently negative
response, whilst many taxon-regional biome groups showed no clear response
to threat in temperate forest and tropical grassland. Our results provide
the first empirical evidence that the taxon-regional biome unit has
potential as a reasonable spatial unit for monitoring how ecological
communities respond to threats and designing effective conservation
interventions to bend the curve on biodiversity loss.