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International audience; Hotspots of tropical marine biodiversity are areas that harbour disproportionately large numbers of species compared to surrounding regions. The richness and location of these hotspots have changed throughout the Cenozoic. Here, we review the global dynamics of Cenozoic tropical marine biodiversity hotspots, including the four major hotspots of the Indo-Australian Archipelago (IAA), western Tethys (present Mediterranean), Arabian Sea and Caribbean Sea. Our review supports the ‘Hopping Hotspots’ model, which proposes that the locations of peak biodiversity are related to Tethyan faunal elements and track broad-scale shallow-marine habitats and high coastal complexity created by the collision of tectonic plates. A null hypothesis is the ‘Whack-A-Mole’ model, which proposes that hotspots occur in habitats suitable for high diversity regardless of taxonomic identity or faunal elements. Earlier ‘Centre-of’ theories (e.g. centres of origin with diversity decreasing with distance from supposed areas of exceptionally high rates of speciation, for which easy connection to adjacent regions to the east and west is important) were based on the analysis of recent biotas with no palaeontological foundation, and may better explain diversity dynamics within a hotspot rather than those between hotspots. More recently, however, human disturbance is massively disrupting these natural patterns.

Marine biodiversity is the essential foundation for the structure and functioning of ocean ecosystems and for providing the full range of ecosystem services that benefit humans on local, regional, and global scales. These benefits include many visible as well as unseen functions and services such as the oxygen we breathe, the seafood we eat, the support of local livelihoods, the marine plants storing 'blue' carbon and protecting our shorelines, the medical and biochemical compounds found in marine species, the coral reefs we explore when scuba diving, and the charismatic creatures inspiring our lives. All these benefits are provided by the diversity and interplay of ocean life, from tiny plankton and bacteria to 30 metre whales and giant kelp.

Despite decades of management and conservation efforts, we have seen only limited success in rebuilding marine life and restoring ocean ecosystems from human-inflicted damage on a global scale. I suggest that we need to harness both our emotional (love) and rational (knowledge) sides to create a more powerful movement to heal the ocean and rebuild its abundance and diversity. Love and compassion fuel our desire and urge for change and provide a compass that can guide our actions. Science and knowledge provide ways for collecting and interpreting data and information that can enhance our understanding and support our decisions and actions. Combining our emotional and rational sides can inspire our thinking and transform our actions in new, creative ways. In order to affect wide-ranging and long-lasting change, love and knowledge need to work together to transform our collective relationship with the ocean.

Climate-induced changes in the world’s oceans will have implications for fisheries productivity and management. Using a model ensemble from the Fisheries and Marine Ecosystem Model Intercomparison Project (Fish-MIP), we analyzed future trajectories of climate-change impacts on marine animal biomass and associated environmental drivers across the North Atlantic Ocean and within the Northwest Atlantic Fisheries Organization (NAFO) convention area and evaluated potential consequences for fisheries productivity and management. Our ensemble results showed that the magnitude of projected biomass changes increased over time and from a low (RCP2.6) to high (RCP8.5) emissions scenario. Within individual NAFO divisions, however, projected biomass changes differed in the magnitude and sometimes direction of change between near (the 2030s) and far future (the 2090s) and contrasting emissions scenarios. By the 2090s, most NAFO divisions with historically (1990-1999) high fisheries landings were projected to experience biomass decreases of 5-40%, while Arctic and subarctic divisions with lower historical landings were projected to experience biomass increases between 20 and 70% under RCP8.5. Future trajectories of sea surface temperature and primary production corroborated that the far-future, high-emissions scenario poses the greatest risk to marine ecosystems and the greatest challenges to fisheries management. Our study summarizes future trends of marine animal biomass and underlying uncertainties related to model projections under contrasting climate-change scenarios. Understanding such climate-change impacts on marine ecosystems is imperative for ensuring that marine fisheries remain productive and sustainable in a changing ocean.

Sustainable Development Goal 14 of the United Nations aims to “conserve and sustainably use the oceans, seas and marine resources for sustainable development”. Achieving this goal will require rebuilding the marine life-support systems that deliver the many benefits that society receives from a healthy ocean. Here we document the recovery of marine populations, habitats and ecosystems following past conservation interventions. Recovery rates across studies suggest that substantial recovery of the abundance, structure and function of marine life could be achieved by 2050, if major pressures—including climate change—are mitigated. Rebuilding marine life represents a doable Grand Challenge for humanity, an ethical obligation and a smart economic objective to achieve a sustainable future.

Harvesting wild seaweeds has a long history and is still relevant today, even though aquaculture now supplies >96% of global seaweed production. Current wild harvests mostly target canopy-forming kelp, rockweed and red macroalgae that provide important ecosystem roles, including primary production, carbon storage, nutrient cycling, habitat provision, biodiversity and fisheries support. Harvest methods range from selective hand-cutting to bottom trawling. Resulting ecosystem impacts depend on extraction method and scale, ranging from changes in primary production to habitat disruption, fragmentation, food-web alterations and bycatch of non-target species. Current management often aims for sustainable harvesting in a single-species context, although some agencies acknowledge the wider ecosystem structure, functions and services seaweeds provide. We outline potential ecosystem-based management approaches that would help sustain productive and diverse seaweed-based ecosystems. These include maintaining high canopy biomass, recovery potential, habitat structure and connectivity, limiting bycatch and discards, while incorporating seasonal closures and harvest-exclusion zones into spatial management plans. Other sustainability considerations concern monitoring, enforcement and certification standards, a shift to aquaculture, and addressing cumulative human impacts, invasive species and climate change. Our review provides a concise overview on how to define and operationalize ecosystem-based management of seaweed harvesting that can inform ongoing management and conservation efforts.

Diatoms often dominate phytoplankton in temperate, polar and upwelling regions. Decreases in silicate availability or silicon to nitrogen (Si:N) ratios may induce silicon limitation in diatoms and lower their proportion within phytoplankton communities. The effects of such changes on the nutritional quality of phytoplankton are not well understood. To examine how changing Si:N ratios affect plankton nutritional value, we applied a range of Si:N ratios on a natural plankton community and manipulated grazing pressure to assess top-down effects of copepod selective grazing. Diatom proportion in phytoplankton increased with increasing Si:N ratios and so did phytoplankton nutritional quality in terms of major fatty acid concentrations, such as polyunsaturated fatty acids, docosahexaenoic (DHA) and eicosapentaenoic (EPA) acids. However, stoichiometric quality (carbon to nitrogen and carbon to phosphorus ratios), DHA:EPA and omega 3:6 (ω3:ω6) ratios declined with increasing Si:N ratios, suggesting that proportions between essential compounds in copepod diet may be more favorable in lowered Si:N ratios. Copepods had a negative effect on DHA contents, DHA:EPA and ω3:ω6 ratios, indicating possible selective grazing on more nutritious plankton. Our findings show that declining silicate concentrations can affect stoichiometric and biochemical quality of phytoplankton, which copepods can also moderate by selective grazing.

Sustainably managed wild fisheries support food and nutritional security, livelihoods, and cultures (1). Harmful fisheries subsidies—government payments that incentivize overcapacity and lead to overfishing—undermine these benefits yet are increasing globally (2). World Trade Organization (WTO) members have a unique opportunity at their ministerial meeting in November to reach an agreement that eliminates harmful subsidies (3). We—a group of scientists spanning 46 countries and 6 continents—urge the WTO to make this commitment...

Climate change is already influencing life in the ocean and will continue to do so into the future with consequences for fisheries and seafood production. Observed physical and chemical climate-change effects alter basic biological processes, such as the survival, growth, and reproduction of marine organisms, the distribution and abundance of target species, the composition and dynamics of marine food webs, and the productivity of ocean ecosystems. Many marine species are moving their range toward the poles, into deeper or more offshore waters to remain at their preferred temperature, while some tropical and polar specialists may disappear. These fundamental changes in species distribution and performance will alter the structure and functioning of food webs and ecosystems. Responding to these changes, marine fisheries need to adapt in terms of where they fish, which species they target, and what catch rate, size, nutritious and monetary value the changing target species have. Available climate-change projections suggest that global fish production and catches are expected to decline, although with considerable regional variation ranging from decreases at lower to increases at higher latitudes. In addition to climate change, a large degree of future trajectories in fisheries production will depend on the development of fisheries operations and other human activities. A reduction in overall fishing pressure, more sustainable fisheries practices, climate-adapted management, and strengthened ocean governance could help maintain marine fisheries and seafood production into the future, and the conservation of ocean ecosystems and marine biodiversity protection could help mitigate some climate and other global change effects.

Ambient temperature is very likely the most important environmental factor determining the distribution and diversity of life in the oceans. Hence, climate change is expected to alter marine biodiversity on a global scale. Here we review observed and predicted effects of climate change on the diversity of marine species. Overall, an increasing number of studies demonstrate that effects of climate change on marine biodiversity are already apparent from local to global scales. So far, long-term fish and plankton monitoring data have provided the most compelling evidence for climate-driven changes in species distribution and diversity, but studies involving other groups such as corals, seaweeds and mammals are increasing. As a general pattern, tropical regions often experience a loss of species due to elevated heat stress, whereas temperate regions increase in diversity, as species migrate poleward. Net increases in diversity are also expected in the polar regions, but so far there are few observations to support this. Complex patterns of change can emerge where ocean warming is accompanied by the effects of sea level rise, acidification, habitat change, changes in ocean circulation, stratification and other aspects of global change. From a management perspective, the conservation of biological diversity will provide insurance and resilience in the face of rapid global change. Cumulative impacts of exploitation, habitat destruction and other threats to biodiversity need to be minimized to maintain the adaptive capacity of marine ecosystems in the present and coming centuries. This might be particularly pressing in tropical regions and developing countries, which will face exceptional socioeconomic and climate-related pressures, as well as in the polar regions, which are faced with a multitude of emerging pressures.

22 pages, 5 figures, 1 table, supplementary information https://doi.org/10.1038/s41558-021-01173-9.-- Data availabilityAll standardized forcing variables from the ESMs are available at https://doi.org/10.48364/ISIMIP.575744.1; all outputs from the MEMs are available via ISIMIP (https://www.isimip.org/gettingstarted/data-access/).-- Code availabilityAll code used to analyse simulations is available at https://github.com/Fish-MIP/CMIP5vsCMIP6, Projections of climate change impacts on marine ecosystems have revealed long-term declines in global marine animal biomass and unevenly distributed impacts on fisheries. Here we apply an enhanced suite of global marine ecosystem models from the Fisheries and Marine Ecosystem Model Intercomparison Project (Fish-MIP), forced by new-generation Earth system model outputs from Phase 6 of the Coupled Model Intercomparison Project (CMIP6), to provide insights into how projected climate change will affect future ocean ecosystems. Compared with the previous generation CMIP5-forced Fish-MIP ensemble, the new ensemble ecosystem simulations show a greater decline in mean global ocean animal biomass under both strong-mitigation and high-emissions scenarios due to elevated warming, despite greater uncertainty in net primary production in the high-emissions scenario. Regional shifts in the direction of biomass changes highlight the continued and urgent need to reduce uncertainty in the projected responses of marine ecosystems to climate change to help support adaptation planning, This work was supported by the Jarislowsky Foundation (D.P.T.), the Natural Sciences and Engineering Research Council of Canada Discovery Grant programme (D.P.T., H.K.L., T.D.E., W.W.L.C., J.P.-A. and V.C.); Australian Research Council (ARC) Discovery Projects DP170104240 (J.L.B. and C.N.), DP190102293 (J.L.B., C.N., A.J.R., J.D.E. and D.P.T.) and DP150102656 (J.D.E.); the European Union’s Horizon 2020 research and innovation programme under grant agreements 817578 (TRIATLAS) (M.C., J.S., L.S., O.M., L.B., Y.-J.S., N.B. and J.R.), 869300 (FutureMARES) (J.A.F.-S.,Y.-J.S. and M.C.) and 862428 (MISSION ATLANTIC (J.A.F.-S, Y.-J.S. and M.C.); the Spanish National Project ProOceans (PID2020-118097RB-I00) (M.C. and J.S.); the Open Philanthropy Project (C.S.H.); the United Kingdom Research and Innovation (UKRI) Global Challenges Research Fund (GCRF) One Ocean Hub (NE/S008950/1) (K.O.-C. and L.S.); the Simons Foundation (nos. 54993, 645921) (G.L.B.); the Belmont Forum and BiodivERsA under the BiodivScen ERA-Net COFUND programme (SOMBEE project, ANR-18-EBI4-0003-01) (Y.-J.S. and N.B.); the MEOPAR Postdoctoral Fellowship Award 2020–2021 and the Ocean Frontier Institute (Module G) (A.B.-B.); the French ANR project CIGOEF (grant ANR-17-CE32-0008-01) (O.M., L.B. and J.R.); the California Ocean Protection Council Grant C0100400, the Alfred P. Sloan Foundation and the Extreme Science and Engineering Discovery Environment (XSEDE) allocation TG-OCE170017 (D.B. and J.G.); the National Oceanographic and Atmospheric Association (NA20OAR4310441, NA20OAR4310442) (C.M.P.). M.C. acknowledges the Severo Ochoa Centre of Excellence accreditation (CEX2019-000928-S) to the Institute of Marine Science (ICM-CSIC)

Many coastal oceans experience not only increased loads of nutrients but also changes in the stoichiometry of nutrient supply. Excess supply of nitrogen and stable or decreased supply of silicon lower silicon to nitrogen (Si:N) ratios, which may decrease diatom proportion in phytoplankton. To examine how Si:N ratios affect plankton community composition and food web structure, we performed a mesocosm experiment where we manipulated Si:N ratios and copepod abundance in a Baltic Sea plankton community. In high Si:N treatments, diatoms dominated. Some of them were likely spared from grazing unexpectedly resulting in higher diatom biomass under high copepod grazing. With declining Si:N ratios, dinoflagellates became more abundant under low and picoplankton under high copepod grazing. This altered plankton food web structure: under high Si:N ratios, edible diatoms were directly accessible food for copepods, while under low Si:N ratios, microzooplankton and phago-mixotrophs (mixoplankton) were a more important food source for mesograzers. The response of copepods to changes in the phytoplankton community was complex and copepod density-dependent. We suggest that declining Si:N ratios favor microzoo- and mixoplankton leading to increased complexity of planktonic food webs. Consequences on higher trophic levels will, however, likely be moderated by edibility, nutritional value or toxicity of dominant phytoplankton species.

Understanding how changes in limiting nutrient availability affect life in the oceans requires interdisciplinary efforts. Here we illustrate this with an example of silicon, one of the most common elements on land which bioavailable form, silicic acid (Si(OH)4), is a limiting nutrient for silicifying primary producers, such as diatoms. Silicic acid concentrations in the pelagic polar and subpolar North Atlantic have declined by 1-2 μM during spring pre-bloom conditions over the past 25 years. Many coastal areas of the North Atlantic region also face decreased relative availability of silicon due to increased riverine supply of nitrogen and phosphorus and stable or declining loads of silicon. Both declining silicic acid concentrations and declining silicon to nitrogen (Si:N) ratios limit the growth of diatoms, which are major primary producers contributing up to a quarter of global primary production.To assess the effects of declining silicon availability on phytoplankton communities we conducted a mesocosm experiment manipulating Si:N ratios and copepod grazing pressure on phytoplankton communities from the Baltic Sea. Declining Si:N ratio affected not only diatom abundance and relative biomass but also their species composition and overall plankton diversity. Our results illustrate the importance of silicon in structuring community composition at the base of temperate marine food webs. Changes in silicic acid concentrations and Si:N ratios, therefore, may have far-reaching consequences on oceanic primary production and planktonic food webs.The decline in silicon concentrations in polar and subpolar North Atlantic waters is attributed to natural multi-decadal variability but is likely amplified by reduced ocean mixing due to increased water temperatures, illustrating the need of international efforts to curb global climate change. The decline in Si:N ratios in coastal oceans also highlights the need for further reduction of nutrient pollution and improved river basin management. This may require interdisciplinary and international approaches to manage anthropogenic perturbations of the silicon cycle.

The ocean is increasingly facing direct and indirect threats from multiple human activities that alter marine ecosystems worldwide. Mitigating these threats requires a global shift in the way people perceive and interact with the marine environment. Marine public perceptions research has emerged as a useful tool to understand public awareness and attitudes towards the sea. This study compares available surveys of public perceptions of marine threats and protection involving >32,000 respondents across 21 countries. Results indicate that 70% of respondents believe the marine environment is under threat from human activities, and 45% believe the threat is high or very high. Yet when asked about the ocean's health, only 15% thought it was poor or threatened. Respondents consistently ranked pollution issues as the highest threat, followed by fishing, habitat alteration and climate change. With respect to ocean protection, 73% of respondents support marine protected areas in their region. Most respondents overestimated the area of ocean currently protected, and would like to see much larger areas protected in the future. Overall, a clear picture emerged of the perceived threats and support for protection which can inform marine managers, policy makers, conservation practitioners and educators to improve marine management and conservation programs.

Following publication of this Article, correspondence with colleagues and subsequent analysis uncovered discrepancies between the spreadsheet containing data from the RAM Legacy Stock Assessment Database we used for this analysis and the content of the database, which is now publicly available1. In particular, a set of numerical entries for ‘spawning stock biomass’ and ‘total stock biomass’ are numerically incorrect or missing in the spreadsheet analysed for the paper. We have been unable to trace back the origin of these differences. As the updated database has now been published online1, we wish to ensure reproducibility by correcting the published record to be consistent with the publicly available database. We have re-run all analyses that use the data in question. This included recalculating: (1) the proportions of stocks in ‘increasing/decreasing/ no change’ biomass categories (Fig. 3a and Supplementary Fig. S2.3 of the original Article); (2) the aggregate B/BMSY time series across all global stocks (Fig. 4a of the original Article); (3) the recovery probabilities for individual stocks currently depleted below BMSY (Fig. 4b of the original Article); and (4) the validation of the BMSY approximation in cases where assessment-estimated BMSY values are not available (Supplementary Fig. S2.2 of the original Article). We made a methodological modification to the way the aggregate B/BMSY was calculated for the original Fig. 4a. We originally weighted each stock by their observed biomass value per year; we now weight by the mean annual biomass calculated across years. The motivation for the original choice was to weight stocks according to their contribution to global biomass. In the corrected database, the time series for Japanese sardine now inappropriately dominates the original calculations. The Japanese sardine is one of the largest stocks in the database. Its stock assessment (as now reflected in the RAM Legacy Stock Assessment Database1) gives an estimate for B/BMSY that exceeded 30.0 during the 1980s and declines to a value of 0.1 in the early 2000s. This represents an overly influential outlier in the database, absent from the previous dataset, in which the vast majority of stocks vary with B/BMSY between 0.01 and 2.0, and very rarely over 3.0 or 4.0. This variation, combined with the large overall size of the stock, make the original weighting untenable because it produces a global aggregate trend that mirrors Japanese sardine through the 1980s and is unrepresentative of the global fishery. Weighting by mean annual biomass was the simplest modification. Calculating the weights in this way achieves the intended goal of weighting stocks according to their contribution to global biomass, while removing the extreme dominance of single large stocks. Because the number of affected stocks is small relative to the total number of analysed stocks (

Globally, lobsters are one of the most economically valuable wild species caught in capture fisheries. Catches are dominated by American lobster (Homarus americanus) landed entirely in Atlantic Canada and northeastern United States. In Atlantic Canada, lobster fishing and marine finfish aquaculture take place in the same coastal waters creating the potential for negative environmental, as well as social, interactions. We review the state of knowledge of environmental interactions between American lobster, their habitat and fishery, and marine finfish aquaculture. We first provide a brief overview of key biological, behavioural, and ecological processes and environmental stressors of American lobster at different life-history stages followed by an overview of the pathways of effects of marine finfish aquaculture on coastal ecosystems in general and on American lobster. Our review found that certain finfish aquaculture-lobster interactions have received considerable study (e.g., chemical use), whereas knowledge of other interactions are either limited (e.g., net pens, waste discharges) or lacking (e.g., disease, noise, lights, and odours). An ecosystem-based approach to aquaculture has been proposed for managing these interactions but implementing this approach has proven to be a challenge in part because of complex multi-sector, multi-stakeholder and multi-agency governance issues. While governance solutions await development, practical measures based on the results of scientific research identified in this review, such as better use of existing oceanographic and bathymetric data, habitat and human impact assessment tools, and toxicity information offer regulators ample information and management tools, at least at the farm- and bay-scale, to avoid negative finfish aquaculture-lobster interactions in Atlantic Canada. Bridging the governance gap will likely require new community-based management models that more effectively identify, generate, and integrate local community and fisher knowledge and concerns.

Synthetic organic polymers—or plastics—did not enter widespread use until the 1950s. By 2015, global production had increased to 322 million metric tons (Mt) year−1, which approaches the total weight of the human population produced in plastic every year. Approximately half is used for packaging and other disposables, 40% of plastic waste is not accounted for in managed landfills or recycling facilities, and 4.8–12.7 Mt year−1 enter the ocean as macroscopic litter and microplastic particles. Here, we argue that such mismanaged plastic waste is similar to other persistent pollutants, such as dichlorodiphenyltrichloroethane (DDT) or polychlorinated biphenyls (PCBs), which once threatened a “silent spring” on land. Such a scenario seems now possible in the ocean, where plastic cannot be easily removed, accumulates in organisms and sediments, and persists much longer than on land. New evidence indicates a complex toxicology of plastic micro- and nanoparticles on marine life, and transfer up the food chain, including to people. We detail solutions to the current crisis of accumulating plastic pollution, suggesting a Global Convention on Plastic Pollution that incentivizes collaboration between governments, producers, scientists, and citizens.

Over the past decades, much research has focused on understanding the critical factors for marine extinctions with the aim of preventing further species losses in the oceans. Although conservation and management strategies are enabling several species and populations to recover, others remain at low abundance levels or experience further declines. To understand these discrepancies, we asked which intrinsic and extrinsic factors are critical for the recovery of marine mammals. Building on a published database on abundance trends of 137 marine mammal populations worldwide, we compiled data on 28 potential critical factors and used random forests and additive mixed models in our analytical approach. Our results highlight that a mix of life-history characteristics, ecological traits, phylogenetic relatedness, population size, geographic range, human impacts and management efforts were important in explaining why populations recover or not. Generally, species with lower age at maturity and intermediate habitat area were more likely to recover, which is consistent with life-history and ecological theory. Body size and ocean basin were also important, as well as trophic level, social interactions, the dominant habitat and habitat disturbance. Overall, our results highlight that not one or two, but a range of intrinsic and extrinsic factors are important for recovery, pointing to cumulative effects. This new line of research provides important information for improving conservation and management strategies particularly for those populations that have been unable to recover to date. This article is protected by copyright. All rights reserved

International audience; Fisheries and aquaculture make a crucial contribution to global food security, nutrition and livelihoods. However, the UN Sustainable Development Goals separate marine and terrestrial food production sectors and ecosystems. To sustainably meet increasing global demands for fish, the interlinkages among goals within and across fisheries, aquaculture and agriculture sectors must be recognized and addressed along with their changing nature. Here, we assess and highlight development challenges for fisheries-dependent countries based on analyses of interactions and trade-offs between goals focusing on food, biodiversity and climate change. We demonstrate that some countries are likely to face double jeopardies in both fisheries and agriculture sectors under climate change. The strategies to mitigate these risks will be context-dependent, and will need to directly address the trade-offs among Sustainable Development Goals, such as halting biodiversity loss and reducing poverty. Countries with low adaptive capacity but increasing demand for food require greater support and capacity building to transition towards reconciling trade-offs. Necessary actions are context-dependent and include effective governance, improved management and conservation, maximizing societal and environmental benefits from trade, increased equitability of distribution and innovation in food production, including continued development of low input and low impact aquaculture.

Eelgrass (Zostera marina) forms extensive beds in temperate coastal and estuarine environments worldwide and provides important ecosystem services, including habitat for a wide range of species as well as nutrient cycling and carbon storage. However, little is known about how eelgrass ecosystem structure and services differ naturally among regions. Using large-scale field surveys, we examined differences in eelgrass bed structure, carbon and nitrogen storage, community composition, and habitat services across three distinct regions in Eastern Canada. We focused on eelgrass beds with low anthropogenic impacts to compare natural differences. In addition, we analyzed the relationships of eelgrass bed structure with environmental conditions, and species composition with bed structure and environmental conditions, to elucidate potential drivers of observed differences. Our results indicate that regional differences in eelgrass bed structure were weakly correlated with water column properties, whereas differences in carbon and nitrogen storage were mainly driven by differences in eelgrass biomass. There were distinct regional differences in species composition and diversity, which were particularly linked to temperature, as well as eelgrass bed structure indicating differences in habitat provision. Our results highlight natural regional differences in ecosystem structure and services which could inform spatial management and conservation strategies for eelgrass beds.

Identificadors digitals: Digital object identifier for the 'European Research Council' (http://dx.doi.org/10.13039/501100000781) and Digital object identifier for 'Horizon 2020' (http://dx.doi.org/10.13039/501100007601) Unidad de excelencia María de Maeztu CEX2019-000940-M Under climate change, species composition and abundances in high-latitude waters are expected to substantially reconfigure with consequences for trophic relationships and ecosystem services. Outcomes are challenging to project at national scales, despite their importance for management decisions. Using an ensemble of six global marine ecosystem models we analyzed marine ecosystem responses to climate change from 1971 to 2099 in Canada's Exclusive Economic Zone (EEZ) under four standardized emissions scenarios. By 2099, under business-as-usual emissions (RCP8.5) projected marine animal biomass declined by an average of −7.7% (±29.5%) within the Canadian EEZ, dominated by declines in the Pacific (−24% ± 24.5%) and Atlantic (−25.5% ± 9.5%) areas; these were partially compensated by increases in the Canadian Arctic (+26.2% ± 38.4%). Lower emissions scenarios projected successively smaller biomass changes, highlighting the benefits of stronger mitigation targets. Individual model projections were most consistent in the Atlantic and Pacific, but highly variable in the Arctic due to model uncertainties in polar regions. Different trajectories of future marine biomass changes will require regional-specific responses in conservation and management strategies, such as adaptive planning of marine protected areas and species-specific management plans, to enhance resilience and rebuilding of Canada's marine ecosystems and commercial fish stocks.

We evaluate the extent of climate change adaptation in the global protected seascape, and identify ways to further advance it., The impacts of climate change and the socioecological challenges they present are ubiquitous and increasingly severe. Practical efforts to operationalize climate-responsive design and management in the global network of marine protected areas (MPAs) are required to ensure long-term effectiveness for safeguarding marine biodiversity and ecosystem services. Here, we review progress in integrating climate change adaptation into MPA design and management and provide eight recommendations to expedite this process. Climate-smart management objectives should become the default for all protected areas, and made into an explicit international policy target. Furthermore, incentives to use more dynamic management tools would increase the climate change responsiveness of the MPA network as a whole. Given ongoing negotiations on international conservation targets, now is the ideal time to proactively reform management of the global seascape for the dynamic climate-biodiversity reality.

Climate change is increasingly impacting marine protected areas (MPAs) and MPA networks, yet adaptation strategies are rarely incorporated into MPA design and management plans according to the primary scientific literature. Here we review the state of knowledge for adapting existing and future MPAs to climate change and synthesize case studies (n = 27) of how marine conservation planning can respond to shifting environmental conditions. First, we derive a generalized conservation planning framework based on five published frameworks that incorporate climate change adaptation to inform MPA design. We then summarize examples from the scientific literature to assess how conservation goals were defined, vulnerability assessments performed and adaptation strategies incorporated into the design and management of existing or new MPAs. Our analysis revealed that 82% of real-world examples of climate change adaptation in MPA planning derive from tropical reefs, highlighting the need for research in other ecosystems and habitat types. We found contrasting recommendations for adaptation strategies at the planning stage, either focusing only on climate refugia, or aiming for representative protection of areas encompassing the full range of expected climate change impacts. Recommendations for MPA management were more unified and focused on adaptative management approaches. Lastly, we evaluate common barriers to adopting climate change adaptation strategies based on reviewing studies which conducted interviews with MPA managers and other conservation practitioners. This highlights a lack of scientific studies evaluating different adaptation strategies and shortcomings in current governance structures as two major barriers, and we discuss how these could be overcome. Our review provides a comprehensive synthesis of planning frameworks, case studies, adaptation strategies and management actions which can inform a more coordinated global effort to adapt existing and future MPA networks to continued climate change.

Future climate impacts and their consequences are increasingly being explored using multi-model ensembles that average across individual model projections. Here we develop a statistical framework that integrates projections from coupled ecosystem and earth-system models to evaluate significance and uncertainty in marine animal biomass changes over the 21st century in relation to socioeconomic indicators at national to global scales. Significant biomass changes are projected in 40%–57% of the global ocean, with 68%–84% of these areas exhibiting declining trends under low and high emission scenarios, respectively. Given unabated emissions, maritime nations with poor socioeconomic statuses such as low nutrition, wealth, and ocean health will experience the greatest projected losses. These findings suggest that climate-driven biomass changes will widen existing equity gaps and disproportionally affect populations that contributed least to global CO2 emissions. However, our analysis also suggests that such deleterious outcomes are largely preventable by achieving negative emissions (RCP 2.6)., Numerous marine ecosystem models are used to project animal biomass over time but integrating them can be challenging. Here the authors develop a test for statistical significance in multi-model ensemble trends, and thus relate future biomass trends to current patterns of ecological and socioeconomic status.

6 pages, 5 figures, supporting information https://doi.org/10.1073/pnas.1900194116.-- All data reported in this paper are archived and publicly available at http://dataservices.gfz-potsdam.de/pik/showshort.php?id=escidoc:2956913., 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, Financial support was provided by the German Federal Ministry of Education and Research through ISI-MIP (Grant01LS1201A1), the European Union’s Horizon 2020 Research and Innovation Program (Grant 678193), and the Ocean Frontier Institute (Module G). We acknowledge additional financial support as follows: to H.K.L., W.W.L.C., and B.W. from the Natural Sciences and Engineering Research Council (NSERC) of Canada; to D.P.T. from the Kanne Rasmussen Foundation Denmark; to A.B.-B. from the NSERC Transatlantic Ocean Science and Technology Program; to W.W.L.C. and T.D.E. from the Nippon Foundation-Nereus Program; to E.D.G., M.C. and J. Steenbeek from the European Union’s Horizon 2020 Re-search and Innovation Program (Grants 682602 and 689518); to E.A.F., J.L.B., andT.R. from Commonwealth Scientific and Industrial Research Organization and the Australian Research Council; to N.B., L.B., and O.M. from the French Agence Nationale de la Recherche and Pôle de Calcul et de Données pour la Mer; and to S.J. from the UK Department of Environment, Food and Rural Affairs