Assessing coral thermal preferences and vulnerability to climate change for targeted conservation

Rising ocean temperatures and marine heat waves associated with climate change cause mass coral bleaching and mortality, leading to population collapse and putting in peril many marine and terrestrial life forms that depend on tropical reefs, including human societies. Reef-building corals are particularly vulnerable to warming temperatures since they have relatively narrow thermal tolerances and often live close to their upper thermal limits. However, thermal conditions in which corals can survive and thrive, and tolerance to thermal stress, differ across species, and often within the same species, due to evolutionary, physiological, and ecological mechanisms. Limited knowledge on species thermal preferences and critical temperature thresholds prevents anticipating where and when coral populations may collapse as temperatures keep rising, which would enable responding with targeted conservation measures. We use a unique ~40 year-long archipelago-scale coral reef monitoring and sea surface temperature dataset to quantify thermal preferences and thresholds of major coral taxa using the broad reef system of New Caledonia representing ~6% of the world’s coral reef habitats. Our analyses quantify upper and lower thermal limits of major coral taxa, identifying species most vulnerable to a warmer future environment and requiring urgent conservation measures, and those more resistant and resilient. Our study facilitates targeted conservation measures for effective biodiversity conservation and coastal adaptation to climate change.