Temporal change and drivers of multiple facets of biodiversity at mesoscales

Abstract

We expect declines, but reported trends and drivers of global biodiversity change vary across taxa, regions, and scales. Most studies focus on a single metric, typically species richness or temporal turnover. They also assess change at either local or global scale, rarely at the intermediate grain, and with limited analyses of the drivers of these changes. Here, we present a near-global study (9 regions across 4 continents) at a novel meso-scale (100–2500 km² contiguous grids), measuring multiple facets of contemporary biodiversity change (species richness, occupancy, temporal and spatial turnover during the past 50 years). We also examine their potential drivers, including temperature, precipitation, human footprint, tree coverage, and cropland area. We account for variation in sampling effort (using Frescalo and Bayesian occupancy models) and we identify both static and dynamic drivers of the change (via Random Forests). We show that 8 out of 9 regions exhibit an increase in mean occupancy per species over time. Most regions are gaining species on average and these changes seem to be driven by temperature, change in temperature and change in precipitation. At smaller grains, we see a weak taxonomic homogenization which vanishes at larger scales. Temporal turnover patterns vary by region and are driven again mostly by changes in temperature and precipitation. Overall, we present the most up-to-date synthesis of temporal biodiversity change and its underlying drivers at a previously underexplored mesoscale.