Red listing the flora of the Green Islands reveals high extinction risk in the Azores

Oceanic islands are global biodiversity hotspots, yet they face disproportionate risks of species extinction. The Azores archipelago holds a unique flora composed of 94 endemic vascular plant taxa (species and subspecies) that are strictly endemic to the Azores, which represents about 32% of the native vascular flora. Here, we present the first comprehensive IUCN Red List assessment of the Azorean endemic vascular flora, based on more than 10,600 curated occurrence records, herbaria specimens, and recent field surveys. We found that nearly 60% of assessed taxa are threatened with extinction, Endangered being the most frequent IUCN category. Two species are confirmed Extinct, and 12 taxa remain Data Deficient due to unresolved taxonomy. The Red List Index (RLI) for Azorean endemics was calculated at 0.602, indicating a concerning level of extinction risk and, importantly, providing a reference point for monitoring future changes in conservation status. Spatial analysis revealed that endemic taxa richness is highly uneven, with most areas hosting few or no endemics. Notably, 12 hotspots occur outside the current protected area network, leaving key refuges for endemic taxa unprotected. These findings underscore the urgent need to expand legal protection, prioritise the management of invasive taxa, restore degraded habitats, and integrate newly described taxa into conservation frameworks. By establishing a baseline for monitoring extinction risk, this study provides a critical tool to guide conservation action in the Azores, and contributes to broader efforts to safeguard the unique natural heritage of oceanic islands.