In the Eye of the Storm: Long-term Impacts of Catastrophic Hurricanes and Rising Sea Levels on Endangered Iguana Populations in the Bahamas
Hayes, William K.
Department of Earth and Biological Sciences
Loma Linda University
Loma Linda, CA
The flora and fauna of archipelagos are particularly vulnerable to climate change. With global warming, we can expect catastrophic storms to increase in frequency and severity, and rising seas to inundate vulnerable habitats. To characterize the long-term impacts of storms on endangered iguanas (Cyclura spp.) in the Bahamas, we examined more than two decades of changes in the populations and habitats of two regions with exceptional storm exposure: San Salvador Island and the Acklins Bight. Iguanas in these regions are largely restricted to small offshore cays, where we conducted population surveys during the period 1994-2016, and analyzed satellite imagery to identify changes in habitat extent and quality. The biggest impacts on population size and habitat were clearly associated with catastrophic storms, notably hurricanes Floyd in 1998 and Joaquin in 2015. Massive storm-generated waves washed up to 50% of adult iguanas and close to 100% of juveniles from some of the cays, depositing many on the nearby mainland, where most or all succumbed to dogs, vehicles, and other sources of mortality. As much as 90% of the critical vegetation was also ripped from the cays, along with much of the soil that held it in place. The overall size of one cays declined markedly with erosion. Some cays fared better than others, depending largely on geophysical features and exposure to the hurricane's path. To assess the effects of rising seas, we used elevation maps to estimate habitat loss corresponding to 1 m and 2 m increases in sea level. The largest iguana populations occur on the lowest-lying cays, and these are most subject to habitat loss. Our findings underscore the potentially devastating impacts of climate change on insular vertebrate populations and the needs for long-term surveillance and conservation management.