Mitigating local human impacts promotes coral reef persistence under climate change

Abstract

Coastal ecosystems are disproportionally inhabited by global human population. Consequently, human impacts originating from land and sea combine with climate-driven disturbances to fundamentally restructure nearshore marine ecosystems. These coincident human stressors are especially acute in the tropics where population centres concentrate along shorelines and marine heatwaves increasingly trigger mass coral bleaching and mortality. However, despite decades of research, we lack consensus as to whether local management supports coral reef resilience under climate change. Here we combined recurring reef surveys with a unique time series of land-sea human impacts over a 20-year period that encompassed an unprecedented marine heatwave in Hawaiʻi. Reefs with high fish biomass and reduced land-based impacts such as wastewater pollution had positive coral trajectories pre-disturbance and experienced minimal coral loss following severe heat stress. Concurrent land-sea management resulted in a 3- to 7-fold increase in the probability of a reef having high reef-builder cover four years post-disturbance. International efforts to conserve 30% of Earth’s ecosystems are gaining momentum, but do not intrinsically link land and ocean conservation targets. Our findings suggest coupled land-sea policy measures are required to realise global conservation goals and provide coral reefs with the best opportunity for persistence in our changing climate.

Anthropogenic climate change will likely outpace coral range expansion

“…Although we did not consider anthropogenic stressors such as overfishing and pollution in our simulations, our results suggest that the presence or absence of non-thermal stressors (such as light limitation) that reduce the baseline growth potential for corals can be the difference between tolerable and catastrophic coral cover decline (figure 7). Indeed, coral reefs in Hawai'i exposed to less pollution and greater fishing restrictions have demonstrated greater resilience to thermal stress (58), so reducing non-thermal stressors where possible will be increasingly essential for limiting unmitigable damage from heat stress.…”