Projected impacts of climate change on marine fish and fisheries

This paper reviews current literature on the projected effects of climate change on marine fish and shellfish, their fisheries, and fishery-dependent communities throughout the northern hemisphere. The review addresses the following issues: (i) expected impacts on ecosystem productivity and habitat quantity and quality; (ii) impacts of changes in production and habitat on marine fish and shellfish species including effects on the community species composition, spatial distributions, interactions, and vital rates of fish and shellfish; (iii) impacts on fisheries and their associatedcommunities; (iv) implications for food security and associated changes; and (v) uncertainty andmodelling skill assessment. Climate change will impact fish and shellfish, their fisheries, and fishery-dependent communities through a complex suite of linked processes. Integrated interdisciplinary research teams are forming in many regions to project these complex responses. National and international marine research organizations serve a key role in the coordination and integration of research to accelerate the production of projections of the effects of climate change on marine ecosystems and to move towards a future where relative impacts by region could be compared on a hemispheric or global level. Eight research foci were identified that will improve the projections of climate impacts on fish, fisheries, and fishery-dependent communities.

Impacts of climate change on marine ecosystem production in societies dependent on fisheries

Growing human populations and changing dietary preferences are increasing global demands for fish, adding pressure to concerns over fisheries sustainability. Here we develop and link models of physical, biological and human responses to climate change in 67 marine national exclusive economic zones, which yield approximately 60% of global fish catches, to project climate change yield impacts in countries with different dependencies on marine fisheries. Predicted changes in fish production indicate increased productivity at high latitudes and decreased productivity at low/mid latitudes, with considerable regional variations. With few exceptions, increases and decreases in fish production potential by 2050 are estimated to be <10% (mean C3.4%) from present yields. Among the nations showing a high dependency on fisheries, climate change is predicted to increase productive potential in West Africa and decrease it in South and Southeast Asia. Despite projected human population increases and assuming that per capita fish consumption rates will be maintained1, ongoing technological development in the aquaculture industry suggests that projected global fish demands in 2050 could be met, thus challenging existing predictions of inevitable shortfalls in fish supply by the mid-twenty-first century. This conclusion, however, is contingent on successful implementation of strategies for sustainable harvesting and effective distribution of wild fish products from nations and regions with a surplus to those with a deficit. Changes in management effectiveness2 and trade practices5 will remain the main influence on realized gains or losses in global fish production.

Impacts of the Oceans on Climate Change

The oceans play a key role in climate regulation especially in part buffering (neutralising) the effects of increasing levels of greenhouse gases in the atmosphere and rising global temperatures. This chapter examines how the regulatory processes performed by the oceans alter as a response to climate change and assesses the extent to which positive feedbacks from the ocean may exacerbate climate change. There is clear evidence for rapid change in the oceans. As the main heat store for the world there has been an accelerating change in sea temperatures over the last few decades, which has contributed to rising sea‐level. The oceans are also the main store of carbon dioxide (CO2), and are estimated to have taken up ∼40% of anthropogenic-sourced CO2 from the atmosphere since the beginning of the industrial revolution. A proportion of the carbon uptake is exported via the four ocean ‘carbon pumps’ (Solubility, Biological, Continental Shelf and Carbonate Counter) to the deep ocean reservoir. Increases in sea temperature and changing planktonic systems and ocean currents may lead to a reduction in the uptake of CO2 by the ocean; some evidence suggests a suppression of parts of the marine carbon sink is already underway. While the oceans have buffered climate change through the uptake of CO2 produced by fossil fuel burning this has already had an impact on ocean chemistry through ocean acidification and will continue to do so. Feedbacks to climate change from acidification may result from expected impacts on marine organisms (especially corals and calcareous plankton), ecosystems and biogeochemical cycles. The polar regions of the world are showing the most rapid responses to climate change. As a result of a strong ice–ocean influence, small changes in temperature, salinity and ice cover may trigger large and sudden changes in regional climate with potential downstream feedbacks to the climate of the rest of the world. A warming Arctic Ocean may lead to further releases of the potent greenhouse gas methane from hydrates and permafrost. The Southern Ocean plays a critical role in driving, modifying and regulating global climate change via the carbon cycle and through its impact on adjacent Antarctica. The Antarctic Peninsula has shown some of the most rapid rises in atmospheric and oceanic temperature in the world, with an associated retreat of the majority of glaciers. Parts of the West Antarctic ice sheet are deflating rapidly, very likely due to a change in the flux of oceanic heat to the undersides of the floating ice shelves. The final section on modelling feedbacks from the ocean to climate change identifies limitations and priorities for model development and associated observations. Considering the importance of the oceans to climate change and our limited understanding of climate-related ocean processes, our ability to measure the changes that are taking place are conspicuously inadequate. The chapter highlights the need for a comprehensive, adequately funded and globally extensive ocean observing system to be implemented and sustained as a high priority. Unless feedbacks from the oceans to climate change are adequately included in climate change models, it is possible that the mitigation actions needed to stabilise CO2 and limit temperature rise over the next century will be underestimated.

ICES and PICES Strategies for Coordinating Research on the Impacts of Climate Change on Marine Ecosystems

The social, economic, and ecological consequences of projected climate change on fish and fisheries are issues of global concern. In 2012, the International Council for the Exploration of the Sea (ICES) and the North Pacific Marine Science Organization (PICES) established a Strategic Initiative on Climate Change Effects on Marine Ecosystems (SICCME) to synthesize and to promote innovative, credible, and objective science-based advice on the impacts of climate change on marine ecosystems in the Northern Hemisphere. SICCME takes advantage of the unique and complementary strengths of the two organizations to develop a research initiative that focuses on their shared interests. A phased implementation will ensure that SICCME will be responsive to a rapidly evolving research area while delivering ongoing syntheses of existing knowledge, thereby advancing new science and methodologies and communicating new insights at each phase.

Impacts of climate change on non-native species

Anthropogenic changes to climate and extreme weather events have already led to the introduction of non-native species (NNS) to the North Atlantic. Regional climate models predict that there will be a continuation of the current trend of warming throughout the 21st century providing enhanced opportunities for NNS at each stage of the invasion process. Increasing evidence is now available to show that climate change has led to the northwards range expansion of a number of NNS in the UK and Ireland, such as the Asian club tunicate Styela clava and the Pacific oyster Crassostrea gigas. Providing definitive evidence though of the direct linkage between climate change and the spread of the majority of NNS is extremely challenging, due to other confounding factors, such as anthropogenic activity. Localised patterns of water movement and food supply may also be complicating the overall pattern of northwards range expansion, by preventing the expansion of some NNS, such as the slipper limpet Crepidula fornicata and the Chilean oyster Ostrea chilensis, from a particular region. A greater understanding of the other aspects of climate change and increased atmospheric CO2, such as increased rainfall, heat waves, frequency of storm events, and ocean acidification may aid in increasing the confidence that scientists have in predicting the long term influence of climate change on the introduction, spread and establishment of NNS.

Modelling the combined impacts of climate change and direct anthropogenic drivers on the ecosystem of the northwest European continental shelf

The potential response of the marine ecosystem of the northwest European continental shelf to climate change under a medium emissions scenario (SRES A1B) is investigated using the coupled hydrodynamics-ecosystem model POLCOMS-ERSEM. Changes in the near future (2030–2040) and the far future (2082–2099) are compared to the recent past (1983–2000). The sensitivity of the ecosystem to potential changes in multiple anthropogenic drivers (river nutrient loads and benthic trawling) in the near future is compared to the impact of changes in climate. With the exception of the biomass of benthic organisms, the influence of the anthropogenic drivers only exceeds the impact of climate change in coastal regions. Increasing river nitrogen loads has a limited impact on the ecosystem whilst reducing river nitrogen and phosphate concentrations affects net primary production(netPP) and phytoplankton and zooplankton biomass. Direct anthropogenic forcing is seen to mitigate/amplify the effects of climate change. Increasing river nitrogen has the potential to amplify the effects of climate change at the coast by increasing netPP. Reducing river nitrogen and phosphate mitigates the effects of climate change for netPP and the biomass of small phytoplankton and large zooplankton species but amplifies changes in the biomass of large phytoplankton and small zooplankton.