Evaluating the effects of climate change in the southern Benguela upwelling system using the Atlantis modelling framework

Abstract

The ocean is affected by multiple anthropogenic stressors including climate change, the effects of which are already evident in many ocean ecosystems. The ABACuS v2 end‐to‐end model together with climate projections from the NEMO‐MEDUSA 2.0 model were used to evaluate the effects of fishing, warming and horizontal and vertical mixing on the southern Benguela upwelling system. Of the drivers examined in this study, warming had the greatest effect on species biomass, with mainly negative effects. The magnitude of the impacts of warming intensified from the RCP 2.6 to the 8.5 emission scenario. Fishing negatively affected demersal and large pelagic fish, which in turn resulted in a biomass increase of forage fish due to a decrease in predation pressure. Water mixing was found to have minor indirect effects on zooplankton biomass and fish. The responses of species and species groups to the combined effects of fishing and warming were approximately equally divided between additive, synergistic and antagonistic. Interpretation of our model results suggests that the southern Benguela system is likely to be affected by climate change, including substantial changes in the abundance of some species important to the region's fisheries. Future planning for fisheries needs to take this into account, including through management that strives to maintain the resilience of key species and the system as a whole. In line with previous studies on the southern Benguela, the results reinforce the importance of including consideration of the indirect and combined impacts of climate change and fishing in management and planning.

Tools to Enrich Vulnerability Assessment and Adaptation Planning for Coastal Communities in Data-Poor Regions: Application to a Case Study in Madagascar

“…Determining exposure to climate-driven impacts is the starting point for assessing the vulnerability of a community or region but, particularly in many developing countries, information on climate drivers is often scarce and incomplete. There is no doubt that reliable higher resolution, regional models can, in general, provide better representation than global models of key regional features (Popova et al, 2016b;Ortega-Cisneros et al, 2018a), but the development of regional models is costly and the capacity to do so is not always available in developing regions. Information from global models can be particularly useful in such cases for forecasting future trends, and the goal of the GLORIA project was to identify, from the very complex outputs from global models, indicators that are most relevant to local needs.…”

The Cumulative Effects of Fishing, Plankton Productivity, and Marine Mammal Consumption in a Marine Ecosystem

“…Previous ecosystem simulation studies have explored the cumulative effects of ocean warming and acidification on the dynamics of fish species, communities, and ecosystems (e.g., Griffith et al, 2011Griffith et al, , 2012Griffith et al, , 2019Ortega-Cisneros et al, 2018). The long-term warming trend in the BC marine ecosystem has been only 0.08 • C per decade for sea surface temperature since recordings started in 1917 and even weaker (0.07 • C) for the subsurface (100-150 m) waters (Greenan et al, 2018).…”

“…Marine ecosystems have been increasingly impacted by both climate-and human-induced drivers that have caused drastic changes in the ecosystems at multiple trophic levels and spatial scales, potentially resulting in species redistributions, altered biodiversity, ecosystem resilience and integrity, and affecting the reference points that are critical for effective resource management (e.g., Stenseth et al, 2002;Fulton, 2011;García-Reyes et al, 2013;Quetglas et al, 2013;Feld et al, 2016;Samhouri et al, 2017;Bonebrake et al, 2018;Le Bris et al, 2018;Ortega-Cisneros et al, 2018;Ramírez et al, 2018;Guo et al, 2019). The cumulative impacts from multiple drivers of change can also cause significant disturbances in socio-economic systems (Bograd et al, 2019).…”

“…In contrast to statistical analyses, simulation experiments using ecosystem models can easily consider the large spatial and temporal scales at which the cumulative effects of multiple drivers of change manifest (Griffith et al, 2011;Fu et al, 2018). Simulation experiments employing ecosystems models have been increasingly conducted during the past 10 years to provide a mechanistic understanding of the impacts of natural and humaninduced drivers of changes on marine ecosystems (Griffith et al, 2011(Griffith et al, , 2012(Griffith et al, , 2019Travers-Trolet et al, 2014;Weijerman et al, 2015;Fu et al, 2018Fu et al, , 2019Ortega-Cisneros et al, 2018). In this study, we applied the ecosystem modeling platform Objectoriented Simulator of Marine Ecosystems (OSMOSE) Shin and Cury, 2004;Fu et al, 2017) to the British Columbia (BC) marine ecosystem (Figure 1) to understand the cumulative impacts of multiple drivers on this ecosystem.…”

Key Challenges in Advancing an Ecosystem-Based Approach to Marine Spatial Planning Under Economic Growth Imperatives

“…The observed impacts of acidification on most model groups were explained by indirect effects since acidification affected only plankton groups in our simulations. However, the impacts of warming were mostly attributed to direct effects on the consumption, growth, mortality and reproduction of model groups (Ortega-Cisneros et al, 2018a).…”