Buried Treasures, Hidden Thresholds: Integrating Cave and Landscape Drivers to Guide Conservation of Amazon Ferruginous Cave Biodiversity

Iron-ore extraction plays a central role in the global economy, but several major mining areas overlap with ecologically unique ferruginous landscapes in the Brazilian Amazon, including caves that harbor endemic and highly specialized invertebrate fauna. Reconciling mineral exploitation with biodiversity conservation requires objective ecological criteria capable of supporting evidence-based decision-making. In this study, we evaluated how cave attributes and surrounding landscape features jointly structure invertebrate communities in pristine ferruginous caves of the Amazon and assessed their relative importance and environmental thresholds. Invertebrates were sampled in 69 iron-ore caves during dry and wet seasons, and 28 environmental variables related to cave morphology, microclimate, trophic resources, lithology, vegetation cover, and external climate were measured in subterranean habitats and adjacent landscapes. Our results demonstrate a clear scale-dependent pattern: cave attributes primarily regulated species richness, troglobitic richness, taxonomic distinctness, and seasonal beta diversity, whereas landscape features exerted stronger control over species composition, including troglobitic assemblages. Threshold analyses identified specific combinations of cave and landscape attributes associated with biologically pristine communities. These findings highlight that assessments of ferruginous cave biodiversity must integrate landscape-scale metrics, be conducted in unaltered environments, and prioritize networks of caves rather than isolated sites. This integrative framework provides robust ecological support for conservation planning and the sustainable management of iron-ore cave systems in the Amazon.