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

Abstract Context Addressing global environmental challenges requires an integrative conservation approach that spans multiple taxonomic groups and trophic levels. The "Conserving Nature’s Stage" strategy promotes the protection of geodiversity – abiotic heterogeneity of the Earth’s surface and subsurface – as a 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 taxonomic group, along with geodiversity, climate, topography, and naturalness 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 (i.e., geological, pedological, hydrological, geomorphological diversity), alongside elevation range, temperature, precipitation and naturalness on species richness across scales. We used two complementary modeling approaches. Regional models were applied to evaluate the overall relationship between geodiversity and species richness across the whole study area. Local models were then used to detect whether this relationship varied from one place to another within the region. Results At the regional scale, geodiversity showed a significant and consistent positive association with species richness for all taxa and spatial resolutions, stronger than climatic, topographic, or naturalness variables. Pedological diversity was the component of geodiversity with the most consistent effect across taxa. At the local scale, we found strong variation in the strength of the biodiversity–geodiversity relationship. Still, these relationships were more consistent 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.