Mismatches in exposure, sensitivity, and adaptive capacity to global change lead to contrasting vulnerability profiles for insular vertebrates | Mismatches in exposure, sensitivity, and adaptive capacity to global change lead to contrasting vulnerability profiles for insular vertebrates: Vulnerability of insular vertebrates

Island biota is currently threatened by global anthropogenic pressures. The limited ability of island species to track suitable conditions, combined with their inherent sensitivity to human pressures, makes insular biota highly vulnerable. While vulnerability assessments have been conducted for climate change or biological invasions individually, the vulnerability of island faunas to multiple global change drivers has not been assessed to date, preventing their inclusion in most global biodiversity policy. Here, we evaluate the relative vulnerability of 266 insular bird and mammal species from 45 islands located in six archipelagos worldwide to multiple threats. We first quantified the current exposure of islands to climate change, land-use change, and biological invasions. We then calculated insular assemblage sensitivity based on species’ ecological characteristics and integrated both biotic and abiotic features to assess the adaptive capacity of insular species in response to these threats. We found a strong variability of exposure and adaptive capacity markers among the six archipelagos, but the mean sensitivity of vertebrate assemblages was similar across islands. High vulnerability scores were found for Hawai’i, the Azores, and the Mascarenes. Climate change and biological invasions were dominant in Hawai’i, while land-use change was dominant in the Mascarenes, the Azores, and the Canaries. In contrast, vertebrate assemblages from the Galapagos and Tristan da Cunha had lower vulnerability to current threats. These contrasting profiles in island vulnerability result in different conservation needs for protecting their biodiversity. Our framework provides a more comprehensive and nuanced understanding of the mechanisms behind the vulnerability of insular biota under global change, a necessary step to effectively preserve island biodiversity and its associated benefits for human societies.