Growth rate and adaptive capacity, not just thermal tolerance, are critical for long-term coral persistence under climate change

Abstract

It is widely assumed that corals with a narrower thermal tolerance and greater bleaching susceptibility are at most risk under anthropogenic climate change. Using a simple eco-evolutionary model, we investigate coral reef futures under climate change through a factorial approach, across millions of simulations. We find that, while corals with low thermal tolerance are indeed at greatest risk of population collapse in the short term, coral population persistence beyond 2050 is instead primarily determined by the maximum population growth rate and additive genetic variance. Anthropogenic climate change exceeds the thermal tolerance of all corals, so adaptive capacity and the ability to rapidly recover from disturbance are critical for long-term persistence. As a result, it is plausible that branching corals could fare better than slower growing, stress-tolerant counterparts in the long term, but only if they can weather the greater acute threats over the coming decades. Since the response timescale of corals to climate change varies considerably across taxa, and due to the particular importance of genetic variance in facilitating evolutionary adaptation, sustainable restoration approaches should aim to conserve a broad range of coral species and genotypes, rather than aiming to optimise one particular trait.