As a consequence of its location at the epicenter of El Niño events, the Galapagos Archipelago provides a model system for studying impacts on coastal ecosystems of extreme thermal anomalies, such as are predicted to become widespread globally as a consequence of climate change. Climate change will presumably affect communities primarily through increasing magnitude and frequency of extreme events comparable to El Niño rather than through gradual changes in ocean climate. We here review data on impacts of El Niño events on Galapagos coastal ecosystems, as inferred from ongoing broad-scale ecological monitoring over the past decade at fixed subtidal sites distributed across the archipelago, plus historical sources of marine ecological data for Galapagos extending over the past century.

Results/Conclusions

Rocky reef communities of fishes, invertebrates and macroalgae have exhibited regime shifts across the.Galapagos Marine Reserve following extreme thermal anomalies over the past 30 years, with greatest changes detected for populations of many species at the time of the 1982/83 El Niño. Despite the regular occurrence of El Niño in the region for millennia, inshore reef communities possess a low apparent level of resilience to extreme warming events, as indicated by little recovery towards pre-existing conditions since 1983. Communities associated with upwelling regions and coral reefs were both disproportionately affected by the 1982/83 El Niño, primarily through associated overgrazing of macroalgae and corals by sea urchins and a huge expansion in the total area occupied by urchin barrens. The removal of large lobster and fish predators by artisanal fishing has probably magnified impacts of ENSO events through a cascade of indirect effects involving urchins. Populations of many macroalgae, invertebrates, fishes, turtles, seabirds and marine mammals across the Galapagos region are predicted to increasingly decline through the next century as a consequence of climate change, putting many endemic species at risk of extinction.