Continent-wide declines in shallow reef life over a decade of ocean warming

Human society is dependent on nature(1,2), but whether our ecological foundations are at risk remains unknown in the absence of systematic monitoring of species' populations(3). Knowledge of species fluctuations is particularly inadequate in the marine realm(4). Here we assess the population trends of 1,057 common shallow reef species from multiple phyla at 1,636 sites around Australia over the past decade. Most populations decreased over this period, including many tropical fishes, temperate invertebrates (particularly echinoderms) and southwestern Australian macroalgae, whereas coral populations remained relatively stable. Population declines typically followed heatwave years, when local water temperatures were more than 0.5 ? above temperatures in 2008. Following heatwaves(5,6), species abundances generally tended to decline near warm range edges, and increase near cool range edges. More than 30% of shallow invertebrate species in cool latitudes exhibited high extinction risk, with rapidly declining populations trapped by deep ocean barriers, preventing poleward retreat as temperatures rise. Greater conservation effort is needed to safeguard temperate marine ecosystems, which are disproportionately threatened and include species with deep evolutionary roots. Fundamental among such efforts, and broader societal needs to efficiently adapt to interacting anthropogenic and natural pressures, is greatly expanded monitoring of species' population trends(7,8).

Automated summary

Human society is dependent on nature, but the lack of systematic monitoring of species' populations makes it unknown whether our ecological foundations are at risk. Knowledge of species fluctuations is particularly inadequate in the marine realm. In this study, the population trends of 1,057 common shallow reef species in Australia over the past decade were assessed. Most populations decreased, including tropical fishes, temperate invertebrates, and southwestern Australian macroalgae, while coral populations remained stable. Heatwaves were found to be a significant factor in population declines, and species abundances tended to decline near warm range edges and increase near cool range edges. Efforts to expand monitoring of species' population trends are crucial for conservation and adaptation to anthropogenic and natural pressures.