Species conservation assessments using the criteria outlined by the International Union for the Conservation of Nature Red List can be compromised by limited data availability. Species-rich tropical plant taxa with numerous microendemics are particularly problematic. This study focusses on the Begonia flora of the Indonesian island of Sulawesi, comprised of 65 herbaceous species mainly found in rainforest habitats. Sixty-two species are Sulawesi endemics, including 20 species restricted to limestone karst landscapes. Forty-eight species are represented by fewer than 10 herbarium collections. Here, we outline and discuss an approach that, despite these data limitations, allows meaningful conservation assessments by integrating analyses of occurrences, data primarily based on remote sensing approaches, including forest landscape integrity, forest cover loss, and land cover, and extent of suitable habitat estimation. The results indicate that most Sulawesi Begonia species are narrow endemics whose rainforest habitats have substantially deteriorated in the last two decades: 27 species are assessed as Critically Endangered, 24 as Endangered, six as Vulnerable, five as Least Concern, and three species are Data Deficient. Conservation action, including extension of the protected area network in Sulawesi with emphasis on areas of old-growth forest and limestone karst landscapes, and strengthening of ex-situ living collections, is recommended.
© 2024. The Author(s).