Global decline of pelagic fauna in a warmer ocean

Pelagic fauna is expected to be impacted under climate change according to ecosystem simulations. However, the direction and magnitude of the impact is still uncertain and still not corroborated by observation-based statistical studies. Here we compile a global underwater sonar database and 20 ocean climate projections to predict the future distribution of sound-scattering fauna around the world’s oceans. We show that global pelagic fauna will be seriously compromised by the end of the twenty-first century if we continue under the current greenhouse emission scenario. Low and mid latitudes are expected to lose from 3% to 22% of animal biomass due to the expansion of low-productive systems, while higher latitudes would be populated by present-day temperate fauna, supporting results from ecosystem simulations. We further show that strong mitigation measures to contain global warming below 2 °C would reduce these impacts to less than half. The authors compile an underwater sonar database to understand the current and future distribution of pelagic fauna in the world’s oceans. They show loss of 3–22% of these fauna in low and mid latitudes under high-emissions scenarios, with impact reduced to less than half if global warming is contained below 2 °C.