Miss Farrah Powell1,2,4, Dr. Erik Franklin3,1, Dr. Camilo Mora1
1Department of Geography and Environment, University of Hawaii at Manoa, Honolulu, United States, 2Department of Geography, University of California Santa Barbara, Santa Barbara, United States, 3Hawaii Institute of Marine Biology, School of Ocean and Earth Science and Technology, University of Hawaii at Manoa, Kaneohe, United States, 4Department of Geography, San Diego State University, San Diego, United States
Increasing atmospheric CO2 concentration is placing spatially divergent stresses on the world’s warm-water coral reefs. Although studies report climate-forced range shifts associated with increasing sea surface temperature (SST) or decreasing seawater aragonite saturation (Ωarag), they focus on each stressor in isolation, thereby inhibiting our understanding of the future trajectory of coral reefs. Using projected ocean conditions for SST and Ωarag derived from 12 Earth System Models under IPCC Representative Concentration Pathways (RCPs) 2.6, 4.5, and 8.5, we simulated changes in the distributions of 730 species of warm-water corals on a decadal scale from 2010 to 2100. To differentiate the spatio-temporal patterns associated with each stressor, and to examine their potential interactive effects, we modeled each species’ distribution assuming changes in SST and Ωarag individually and in combination. By 2100, ~ 41.4% and ~87.6% of the world’s coral reefs will lose 80-100% of their range due to concurrent changes in SST and Ωarag under RCP 2.6 and RCP 8.5, respectively. The highest species extirpation rates are expected in the Indo-Pacific, whereas the most immediate threat is expected in the Atlantic. Ensemble model projections show that species’ distribution centroids are expected to shift poleward at a rate of 22.4 and 48.7 km decade-1 under RCP 2.6 and RCP 8.5, respectively. The fastest rate of change in distribution centroids occurs in 2030 under the combined impacts of both stressors. These results strongly suggest that coral reef ecosystems will change rapidly, and immediate action is required to mitigate the impacts of ongoing climate change.
Farrah Powell is a PhD student in the Joint Doctoral Geography program with SDSU and UCSB. She obtained her Bachelor’s degree in Geography and Environmental Studies at UCLA in 2013 where she used remotely sensed imagery to predict harmful algae blooms in the Philippines. She obtained her Master’s degree in Geography from University of Hawaii Manoa working with Dr. Camilo Mora where she focused on climate change impacts on coral reefs. Her current PhD research focuses on social-ecological impacts of climate change on Spiny lobster and Pacific sardine fisheries in the California Current Ecosystem. She integrates qualitative and quantitative methodological techniques in her current research with a concerted focus on human-environment dynamics.