Our Common Future Under Climate Change

There are global concerns over the potential impacts of global environmental change on marine ecosystems and the services they provide. Initial assessments indicate geographically diverse impacts (Cheung et al. 2010), with significant consequences for the wellbeing of dependent communities (Barange et al. 2014). In March 2015, the IOC-ICES-PICES 3rd International Symposium on the Effects of Climate Change on the World�s Oceans was held in Santos (Brazil). This symposium followed the recent IPCC 5th Assessment Report, which included a number of dedicated ocean chapters. The symposium was a significant event in the challenge to provide evidences and project impacts of climate change on ocean physics and biogeochemistry, ecology, phenology and biodiversity, fisheries and foodwebs, as well as on the use and communication of uncertainties in projection methodologies. In this presentation, the convenors of the IOC-ICES-PICES 3rd International Symposium on the Effects of Climate Change on the World�s Oceans, will summarise the main results and highlights of the conference, to update the research and user community on the rapidly developing research field of oceans and climate change.�

Barange, M., Merino, G., Blanchard, J. L., Scholtens, J., Harle, J., Allison, E. H., Allen, J., Holt, J. & Jennings, S. (2014). Impacts of climate change on marine ecosystem production in fisheries-dependent societies. Nature Climate Change, 4, 211-216.�

Cheung, W. et a: 2010. Large-Scale redistribution of maximum fisheries catch potential in the global ocean under climate change. Global Change Biology. 16 (1). 24-35.

Increasing computational power, improved fidelity of climate models and data obtained by global observing networks have advanced our understanding of both climate change and climate model evaluation. In addition, Coupled Model Intercomparison Projects (CMIPs) have contributed to improving climate model ability to reproduce past climates as well as climate variability through the use of ensemble modeling approaches. Nevertheless, typical model resolution is a half to one degree in latitude/longitude in the ocean model component, which makes it difficult to represent many ocean structures and phenomena important to marine ecosystems (e.g. upwelling, western boundary currents, eddies). Coastal areas are some of the most productive and biodiverse regions, and are dominated by mesoscale phenomena, which cannot be properly resolved by the climate models.� One approach that is being used to achieve regional high-resolution climate-scale simulations is by �nesting of a high-resolution limited-area model within a lower resolution large-scale model. Typically, information is downscaled from the coarse- to the fine-resolution region through an overlap in the domains. The high-resolution nest can explicitly resolve features missing from the large-scale model. However, when making a future projection, regional changes may also possibly affect the global climate (i.e. upscaling effects). �Furthermore, model requirements are often different when considering ecosystems. For example, phenology is one of the most important items for marine ecosystems; a slight difference in the start of the spring stratification may result in a quite different marine ecosystem response.

Earth system models (ESMs), which include the carbon cycle, couple physics to lower-trophic-level marine ecosystem models. A common major weakness of ESMs �lower-trophic-level models is the coarse functional group representation of zooplankton and lack of calibration with zooplankton abundances. This is partly because of the lack of a global database for �zooplankton and partly because ESMs lower-trophic-level models have been designed to obtain accurate simulations of nutrient cycling and primary production but not necessarily for zooplankton dynamics. Nevertheless, zooplankton is a key component of marine ecosystems and it is our challenge to improve their representation, as well as the full marine ecosystem in climate models.

Seafood is an important source of livelihood, nutrition and culture to many people, in particular, those in coastal communities. The Fifth Assessment Report of Intergovernmental Panel on Climate Change (IPCC AR5) highlights that climate change (CC) is challenging sustainable management of fisheries by redistributing fish stocks and therefore catches, particularly with many tropical regions suffering decreases in fisheries production. Overfishing further exacerbates climate risks on fisheries by depleting fish stocks while stock rebuilding is expected to help improve climate-resilience. However, quantitative assessment of the contribution of stock rebuilding in reducing the vulnerability of global marine fisheries to CC, with considerations of projection uncertainties, is not included in IPCC AR5. Using multiple climate-living marine resources models driven by a range of emission and fisheries scenarios, we examine the scope of vulnerability reduction of fisheries under CC and different pathways to stock rebuilding. We show that both CC and fishing scenarios contribute significantly to changes in global fisheries yields in 2050. Overall, stock rebuilding increases climate-resilience of the fishing sectors and marine ecosystems. However, even with stock rebuilding, substantial climate risks, particularly in sensitive ecosystems such as tropical oceans, may not be avoided without substantial reduction in greenhouse gas emission. Our results highlight the need for implementing integrated mitigation-adaptation approaches to improve climate-resilience for the fisheries sectors.�

Climate change represents a host of challenges and opportunities for the regulation of fishing effort. Stock displacement may lead to new and improved fishing opportunities in certain locations in a short time, while for other species climate change may truncate their natural ranges and biological processes. Fisheries management bodies will face difficult and often highly politicised choices in addressing the future regulation of fishing effort. These developments will clearly have a considerable impact both on fishing economy, society and the legal norms governing fisheries management and allocations. This paper accordingly examines the implications for international oceans governance raised by the impact of climate change on global fisheries, from both a societal and regulatory standpoint.

This paper will first examine the fundamental challenges posed to legal and societal governance by global climate change in the context of fisheries, identifying faultlines within the current regulatory regime advanced under the law of the sea that will be most affected by shifts in fish populations. This paper then moves to examine a case-study of how RFMOs and other regulators have responded to population shifts and climate-induced reductions in fish stocks in the emergent regulation of new and exploratory fisheries. To this end, it will be demonstrated that RFMOs exhibit strong potential to regulate new fishing effort in a precautionary manner and in accordance with ecosystem-based management, perhaps in contrast to the way in which many current stocks are being managed, although the process remains nascent and iterative.

This paper also acknowledges that stock mobility and regime changes could result in immediate stresses to those are considered to be vulnerable socially and economically. Accordingly, this paper will examine the response of small-scale fisheries (with a particular emphasis on indigenous groups) to climate-induced changes to populations, noting the potential implications to these communities. These elements will accordingly frame an appraisal of current and emerging demands upon fisheries governance and evaluate the ability of the present system to address human dimensional impacts of climate change on fisheries across global and local scales.

The industrial development of High Seas pelagic fisheries targetting tuna and associated (billfishes) species since the 1950s has taken place in a warming Ocean. The short-living skipjack tuna is the most tropical and productive species while bluefin tuna is the most temperate and long living species, providing small but extremely valuable levels of catch. Rather than a single oceanic habitat, these species have overlapping vertical and horizontal habitats defined by their preferences and tolerances developed over the evolution for several key physical and biological variables. Though some tuna and billfishes can move far in high latitudes searching for rich foraging grounds they all return to warm waters (roughly >24�C) for spawning, leading to seasonal migrations and complex population dynamics mechanisms interacting with several environmental variables. Therefore, characterizing habitats and projecting them in the future using IPCC scenarios is a useful but incomplete approach when investigating the impact of climate change on these species. The progress in the study of climate change impacts on tuna and associated species is reviewed with highlights on recent results based on a modeling framework developed to simulate the spatial dynamics of fish with mechanisms constrained by relationships based on the bio-physical environment predicted from coupled 3D models of ocean physics and biogeochemistry. This framework includes a Maximum likelihood Estimation approach allowing reconstructing past history of fish population, to dissociate fishing impacts from natural variability, and to forecast population dynamics under climate change scenarios.