Five Decades of Citizen Science Reveal Erosion of Hotspots of Multifaceted Plant Diversity

ABSTRACT

Biodiversity includes taxonomic, phylogenetic, and functional diversity but the changes in these facets at regional scales remain unclear and often context dependent. Using 2.5 million citizen science observations of 1957 vascular plant species across 53 years in SW‐Germany, we assessed changes in seven biodiversity metrics. Rather than a general decline, we found different facets exhibited different trends in both direction and magnitude of change. Phylogenetic and taxonomic diversity change were mostly negatively correlated, and change in functional diversity was independent from the others. We identified the role of climate and human activity influencing the change in taxonomic and functional diversity, while phylogenetic diversity was also affected by geodiversity. Crucially, we detected consistent erosion of biodiversity hotspots across all facets, while areas with low initial diversity tended to gain species. These findings highlight the need to consider multiple biodiversity facets and local context dependency to better understand biodiversity change at regional scales.