Heightened extinction risk due to tropical cyclones in insular biodiversity hotspots

Abstract

Tropical Cyclones (TCs) represent a serious and potentially growing threat to global biodiversity, although spatial patterns in the severity of this threat are poorly explored. We provide the first global-scale analysis of TC-related extinction risk by examining both their frequency and the number of species they directly threaten in insular biodiversity hotspots; widely recognized spatial units representing both exceptional biodiversity and elevated threat. We first identified which insular hotspots possessed a theoretically high TC-related extinction risk by plotting 50 years of storm tracks for severe (category 4 and 5) TCs (STCs) and determined the frequency with which they occur within each insular hotspot. We then used IUCN Red List data to determine numbers of terrestrial vertebrates in each ‘high risk’ insular hotspot considered to be directly threatened with extinction by STCs. Five insular hotspots (Japan, Polynesia-Micronesia, Philippines, Madagascar and the Indian Ocean Islands, Caribbean Islands) were identified as being ‘high risk’, together accounting for &gt;95 % of STCs falling within insular hotspots. However, the numbers of TC-threatened species in these hotspots varied greatly, from 128 in the Caribbean Islands (which encountered the fewest STCs of all ‘high risk’ hotspots) to eight in Japan (which received the most STCs). Results therefore indicate that TC-related extinction risk is not related to STC frequency, and other ecological and geographical factors are likely to be important drivers of risk. Regardless, our results show that several insular hotspots, particularly the Caribbean Islands, support many species at immediate risk of TC-driven extinction, and these require urgent conservation action. We advocate for the creation of an IUCN task force to oversee conservation strategies aimed at preventing extinctions of severely range-restricted storm-threatened species. We provide a watchlist of 60 such species with a particularly high risk of extinction which should be the initial focus for such a working group.</p