Coral reefs have been degraded by human activities over time, beginning historically with overfishing, and more recently followed by pollution, habitat destruction, and climate change. Because of these combined impacts, coral reef fishes have declined in abundance, size, and biomass over time, and reef fish food webs have become shorter and less resilient. This global degradation started under the impacts of fishing long before we started studying coral reef fishes in a systematic way. Because of that, our perception of what was natural – our baseline – is biased, and is shifting over time as new generations develop their own baselines based on their own personal experience. Most of our understanding of coral reefs came from reefs that were somehow degraded, where large predators were just a memory and fish populations were dominated by small species from lower trophic levels. But in the last 20 years, the birth of the field of marine historical ecology, the study of previously unexplored remote coral reefs, and the recovery of fishes in effective no-take marine reserves have provided a proxy for what reef fish assemblages used to look like prior to human exploitation. Resetting the ecological baseline is crucial for understanding the true magnitude of human impacts on coral reefs, for properly evaluating the efficacy of our management actions, and as a benchmark for coral reef conservation.

THE SHIFTING BASELINE SYNDROME

In 1995, fisheries biologist Daniel Pauly published a seminal paper describing what he called the “shifting baseline syndrome” in fisheries [1937]. According to Pauly, fisheries scientists accepted as a baseline the stock size that occurred when they started their careers. Since the stocks tend to decline over time because of overexploitation, the next generation will adopt a diminished baseline. Everything that baseline is used for – such as determining the total allowable catch for a species – will be biased because the baseline has shifted relative to former baselines [1226,1528,1963]; a process also termed “environmental generational amnesia” in other fields [1712].