Unveiling the spatial link between geodiversity and biodiversity: a multi-taxon study in the South of France

Context: Addressing global environmental challenges requires an integrative conservation approach that spans multiple taxonomic groups and trophic levels. The "Conserving Nature’s Stage" (CNS) strategy promotes the protection of geodiversity -abiotic heterogeneity of the Earth’s surface and subsurface- as an holistic metric for biodiversity and ecosystems conservation, yet its relationship with biodiversity across multiple taxa and trophic levels remains underexplored. Objectives: This study investigates the links between geodiversity and biodiversity at the regional scale in Occitanie (southern France) across three taxonomic groups representing distinct trophic levels: vascular plants (producers), butterflies (primary consumers), and birds (ranging from primary consumers to apex predators). Methods: Species richness for each group, along with geodiversity components, climate, topography, and human footprint metrics, were aggregated within spatial meshes of 5 km, 7.5 km, and 10 km resolution. We applied spatially explicit models to quantify the effects of overall and component-specific geodiversity, alongside classical environmental variables, on species richness across scales. Results: Geodiversity showed a significant and consistent positive association with species richness for all taxa and spatial resolutions, more robust than climatic, topographic, or naturalness variables. Pedological diversity is the component of geodiversity that shows the most consistent effect across taxa. At local scales, spatial non-stationarity was observed, though biodiversity–geodiversity relationships remained more stable across taxa than those involving other environmental predictors. Conclusion: Our findings highlight geodiversity—particularly pedodiversity—as a key, underutilized predictor of multi-taxa diversity. We thus advocate its integration into conservation and landscape planning strategies aimed at systemic biodiversity protection and restoration.