The vulnerability of shellfish aquaculture to climate change and ocean acidification– a global assessment

Human-induced climate change and ocean acidification (CC-OA) is changing the physical and biological processes occurring within the marine environment, with poorly understood implications for marine life. Within the aquaculture sector, molluscan culture is a relatively benign method of producing a high-quality, healthy and sustainable protein source for the expanding human population.  We modelled the Vulnerability of global bivalve mariculture to impacts of CC-OA over the period 2020 to 2100, under RCP8.5.  Vulnerability, assessed at the national level, was dependent on CC-OA-related Exposure, taxon-specific Sensitivity and Adaptive capacity in the sector.  Exposure risk increased over time from 2020 to 2100, with ten nations predicted to experience Very-high Exposure to CC-OA in at least one decade during the period 2020 - 2100. Predicted high Sensitivity in developing countries resulted, primarily, from the cultivation of species that have a narrow habitat tolerance, whilst in some European nations (France, Ireland, Italy, Portugal and Spain) high Sensitivity was attributable to the relatively high economic value of the shellfish production sector.  Predicted Adaptive capacity was low in developing countries primarily due to governance issues, while in some developed countries (Denmark, Germany, Iceland, Netherlands, Sweden, and the United Kingdom) it was linked to limited species diversity in the sector.  Developing and least developed nations (n = 15) were predicted to have the highest overall Vulnerability.  Across all nations, 2060 was identified as a tipping point where predicted CC-OA will be associated with the greatest challenge to shellfish production.  However, rapid declines in mollusc production are predicted to occur in the next decade for some nations, notably North Korea.  Shellfish culture offers human society a low-impact source of sustainable protein.  This research highlights, on a global scale, the likely extent and nature of the CC-OA related threat to shellfish culture and this sector enabling early-stage adaption and mitigation.