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June 11, 2019

Global ensemble projections reveal trophic amplification of ocean biomass declines with climate change

Publisher: Proceedings of the National Academy of Science of the United States

Funders: European Union's Horizon 2020 Research and Innovation Program , Australian Research Council, Commonwealth Scientific and Industrial Research Organization, French Agence Nationale de la Recherche, German Federal Ministry of Education and Research, Kanne Rasmussen Foundation Denmark, Natural Sciences and Engineering Research Council (NSERC) of Canada, Nippon Foundation-Nereus Program, NSERC Transatlantic Ocean Science and Technology Program, Ocean Frontier Institute, Pôle de Calcul et de Données pour la Mer, UK Department of Environment, Food and Rural Affairs

Authors: Andrea Bryndum-Buchholz, Catherine M. Bulman, Daniele Bianchi, David A. Carozza, Derek P. Tittensor, Elizabeth A. Fulton, Eric D. Galbraith, Heike K. Lotze, John P. Dunne, José A. Fernandes, Julia L. Blanchard, Laurent Bopp, Manuel Barange, Marta Coll, Matthias Büchner, Miranda C. Jones, Nicolas Barrier, Olivier Maury, Ricardo Oliveros-Ramos, Simon Jennings, Steve Mackinson, Susa Niiranen, Tilla Roy, Tyler D. Eddy, Villy Christensen, William W.L. Cheung

Language: English

While the physical dimensions of climate change are now routinely assessed through multimodel intercomparisons, projected impacts on the global ocean ecosystem generally rely on individual models with a specific set of assumptions. To address these single-model limitations, we present standardized ensemble projections from six global marine ecosystem models forced with two Earth system models and four emission scenarios with and without fishing. We derive average biomass trends and associated uncertainties across the marine food web. Without fishing, mean global animal biomass decreased by 5% (±4% SD) under low emissions and 17% (±11% SD) under high emissions by 2100, with an average 5% decline for every 1 °C of warming. Projected biomass declines were primarily driven by increasing temperature and decreasing primary production, and were more pronounced at higher trophic levels, a process known as trophic amplification. Fishing did not substantially alter the effects of climate change. Considerable regional variation featured strong biomass increases at high latitudes and decreases at middle to low latitudes, with good model agreement on the direction of change but variable magnitude. Uncertainties due to variations in marine ecosystem and Earth system models were similar. Ensemble projections performed well compared with empirical data, emphasizing the benefits of multimodel inference to project future outcomes. Our results indicate that global ocean animal biomass consistently declines with climate change, and that these impacts are amplified at higher trophic levels. Next steps for model development include dynamic scenarios of fishing, cumulative human impacts, and the effects of management measures on future ocean biomass trends.