• Energy Research

AbstractAquaculture is the world's most diverse farming practice in terms of number of species, farming methods and environments used. While various organizations and institutions have promoted species diversification, overall species diversity within the aquaculture industry is likely not promoted nor sufficiently well quantified. Using the most extensive dataset available (FAO‐statistics) and an approach based on the Shannon Diversity index, this paper provides a method for quantifying and mapping global aquaculture species diversity. Although preliminary analyses showed that a large part of the species forming production is still qualified as undetermined species (i.e. ‘not elsewhere included’); results indicate that usually high species diversity for a country is associated with a higher production but there are considerable differences between countries. Nine of the top 10 countries ranked highest by Shannon Diversity index in 2017 are from Asia with China producing the most diverse collection of species. Since species diversity is not the only level of diversity in production, other types of diversity are also briefly discussed. Diversifying aquatic farmed species can be of importance for long‐term performance and viability of the sector with respect to sustaining food production under (sometimes abrupt) changing conditions. This can be true both at the global and regional level. In contrast, selection and focus on only a limited number of species can lead to rapid improvements in terms of production (towards sustainability or not) and profitability. Therefore, benefits and shortcomings of diversity are discussed from both economical and social‐ecological perspectives that concurrently are shaping the expanding aquaculture industry.

AbstractThe Mediterranean Sea has been defined “under siege” because of intense pressures from multiple human activities; yet there is still insufficient information on the cumulative impact of these stressors on the ecosystem and its resources. We evaluate how the historical (1950–2011) trends of various ecosystems groups/species have been impacted by changes in primary productivity (PP) combined with fishing pressure. We investigate the whole Mediterranean Sea using a food web modelling approach. Results indicate that both changes in PP and fishing pressure played an important role in driving species dynamics. Yet, PP was the strongest driver upon the Mediterranean Sea ecosystem. This highlights the importance of bottom-up processes in controlling the biological characteristics of the region. We observe a reduction in abundance of important fish species (~34%, including commercial and non-commercial) and top predators (~41%), and increases of the organisms at the bottom of the food web (~23%). Ecological indicators, such as community biomass, trophic levels, catch and diversity indicators, reflect such changes and show overall ecosystem degradation over time. Since climate change and fishing pressure are expected to intensify in the Mediterranean Sea, this study constitutes a baseline reference for stepping forward in assessing the future management of the basin.

Marine fisheries have endured for centuries but the last 50 yr have seen a drastic increase in their reach and intensity. We generated global estimates of biomass for marine ecosystems and evaluated the effects that fisheries have had on ocean biomass since the 1950s. A simple and versatile ecosystem model was used to represent ecosystems as a function of energy fluxes through trophic levels (TLs). Using primary production, sea surface temperature, transfer efficiency, fisheries catch and TL of species, the model was applied on a half-degree spatial grid covering all oceans. Estimates of biomass by TLs were derived for marine ecosystems in an unexploited state, as well as for all decades since the 1950s. Trends in the decline of marine biomass from the unexploited state were analyzed with a special emphasis on predator species as they are highly vulnerable to overexploitation. This study highlights 3 main trends in the global effects of fishing: (1) predators are more affected than organisms at lower TLs

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.

Abstract. Model intercomparison studies in the climate and Earth sciences communities have been crucial to building credibility and coherence for future projections. They have quantified variability among models, spurred model development, contrasted within- and among-model uncertainty, assessed model fits to historical data, and provided ensemble projections of future change under specified scenarios. Given the speed and magnitude of anthropogenic change in the marine environment and the consequent effects on food security, biodiversity, marine industries, and society, the time is ripe for similar comparisons among models of fisheries and marine ecosystems. Here, we describe the Fisheries and Marine Ecosystem Model Intercomparison Project protocol version 1.0 (Fish-MIP v1.0), part of the Inter-Sectoral Impact Model Intercomparison Project (ISIMIP), which is a cross-sectoral network of climate impact modellers. Given the complexity of the marine ecosystem, this class of models has substantial heterogeneity of purpose, scope, theoretical underpinning, processes considered, parameterizations, resolution (grain size), and spatial extent. This heterogeneity reflects the lack of a unified understanding of the marine ecosystem and implies that the assemblage of all models is more likely to include a greater number of relevant processes than any single model. The current Fish-MIP protocol is designed to allow these heterogeneous models to be forced with common Earth System Model (ESM) Coupled Model Intercomparison Project Phase 5 (CMIP5) outputs under prescribed scenarios for historic (from the 1950s) and future (to 2100) time periods; it will be adapted to CMIP phase 6 (CMIP6) in future iterations. It also describes a standardized set of outputs for each participating Fish-MIP model to produce. This enables the broad characterization of differences between and uncertainties within models and projections when assessing climate and fisheries impacts on marine ecosystems and the services they provide. The systematic generation, collation, and comparison of results from Fish-MIP will inform an understanding of the range of plausible changes in marine ecosystems and improve our capacity to define and convey the strengths and weaknesses of model-based advice on future states of marine ecosystems and fisheries. Ultimately, Fish-MIP represents a step towards bringing together the marine ecosystem modelling community to produce consistent ensemble medium- and long-term projections of marine ecosystems.