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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.

As atmospheric CO2 levels continue to rise so too does the risk of severe impacts. Scientists clearly have an important role to play in preparing for and responding to climate change impacts; however, calls by scientists for global action have not led to the required changes. It is timely, therefore, for scientists to critically consider their own approach toward climate change research, particularly if we are to ameliorate or adapt to unwanted outcomes. Here we present three different pathways that allow scientists and scientific institutions to conceptualize the implications of their responses to climate change scenarios. These pathways are illustrated via three plausible futures for the marine environment under climate change. This approach allows future responsibilities, outcomes, and implication to be explored within and across pathways and can be applied to different scenarios for scientists and scientific institutions to anticipate and better prepare to contribute effectively to the future. Plain Language Summary: There is mounting evidence that impacts of climate change pose significant risks to society and human well‐being. The pace of large‐scale action on climate change is, however, insufficient to substantially reduce the likely future impacts. These are risks that this generation is imposing on future generations. In this context we outline a framework for scientists and scientific institutions to explore and assess the outcomes and implications of choosing different pathways (inactive, reactive, and proactive) in response to climate change. We developed three illustrative examples of plausible futures under climate change to demonstrate the implications of each of these pathways. We also outline a conceptual framework based on three factors: (i) potential to mitigate, (ii) impact of risk, and (iii) uncertainty in science that will assist scientists and scientific institutions to make informed decisions regarding their responses to global environmental change. Key Points: The implications of three pathways for scientists to respond to climate change are discussed such as maintaining trust in scienceA conceptual model is presented based on three factors: (i) potential to mitigate, (ii) impact of risk, and (iii) uncertainty in scienceA framework to assist scientists and scientific institutions to make informed decisions in response to global environmental change is outlined [ABSTRACT FROM AUTHOR]

Since the 1950s, invertebrate fisheries catches have rapidly expanded globally to more than 10 million tonnes annually, with twice as many target species, and are now significant contributors to global seafood provision, export, trade and local livelihoods. Invertebrates play important and diverse functional roles in marine ecosystems, yet the ecosystem effects of their exploitation are poorly understood. Using 12 ecosystem models distributed worldwide, we analysed the trade-offs of various invertebrate fisheries and their ecosystem effects as well as ecological indicators. Although less recognized for their contributions to marine food webs, our results show that the magnitude of trophic impacts of invertebrates on other species of commercial and conservation interest is comparable with those of forage fish. Generally, cephalopods showed the strongest ecosystem effects and were characterized by a strong top-down predatory role. Lobster, and to a lesser extent, crabs, shrimp and prawns, also showed strong ecosystem effects, but at lower trophic levels. Benthic invertebrates, including epifauna and infauna, also showed considerable ecosystem effects, but with strong bottom-up characteristics. In contrast, urchins, bivalves, and gastropods showed generally lower ecosystem effects in our simulations. Invertebrates also strongly contributed to benthic-pelagic coupling, with exploitation of benthic invertebrates impacting pelagic fishes and vice versa. Finally, on average, invertebrates produced maximum sustainable yield at lower levels of depletion (~45%) than forage fish (~65%), highlighting the need for management targets that avoid negative consequences for target species and marine ecosystems as a whole. [ABSTRACT FROM AUTHOR]