Observed impacts and projected risks of climate change on marine ecosystems

William W.L. Cheung, The University of British Columbia, Institute for the Oceans and Fisheries, Vancouver, BC, Canada, Javier Aristegui, Instituto de Oceanografía y Cambio Global (IOCAG), Universidad de Las Palmas de Gran Canaria, Las Palmas, Spain, Nathaniel L. Bindoff, University of Tasmania, Institute for Marine and Antarctic Studies, Hobart, TAS, Australia, Valeria Guinder, Consejo Nacional de Investigaciones Científicas y Técnicas, Monaco, Monaco, Robert Hallberg, NOAA/Geophysical Fluid Dynamics Laboratory, Princeton, United States, Nathalie Hilmi, Monaco Scientific Centre, Monaco, Monaco, Nianzhi Jiao, Xiamen University, Xiamen, China, James G. Kairo, Kenya Marine and Fisheries Institute, Kenya, Saiful Karim, Queensland University of Technology, Brisbane, QLD, Australia, Toshio Suga, Tohoku University, Graduate School of Science, Sendai, Japan, Lisa A Levin, Scripps Institution of Oceanography, University of California San Diego, La Jolla, United States, Sean ODonoghue, Climate Change Adaptation Branch City of Durban, Durban, South Africa, Sara Purca Cuicapusa, Instituto del Mar del Peru, Peru, Baruch Rinkevich, Israel Oceanographic and Limnological Research, Haifa, Israel, Alessandro Tagliabue, University of Liverpool, Earth, Ocean and Ecological Sciences, Liverpool, L69, United Kingdom and Phillip Williamson, University of East Anglia, Norwich, United Kingdom
Abstract:
Marine ecosystems, from the coast to open ocean and the deep seafloor, are exposed to increasing climate change-related hazards from changing environmental conditions. The IPCC Special Report for the Oceans and Cryosphere in the Changing Climate (SROCC) synthesizes new evidence since the Fifth Assessment Report to assess observed impacts and projected future risks on marine organisms, biological communities and food webs in relation to the effects of multiple climate and non-climate hazards. These key hazards to marine ecosystems include ocean warming, oxygen loss, acidification, sea level rise, changes in net primary production and export production, as well as their interactions with coastal development, nutrient run-off and overfishing. The report concludes that geographical range and phenological shifts of a wide variety of marine species have occurred since the 1950s in response to ocean warming and biogeochemical changes to their habitats. These shifts altered species interactions, causing cascading effects on ecosystem functions. Also, coastal ecosystems are already under stress from ocean warming and sea level rise that are exacerbated by non-climatic pressures from human activities on ocean and land. Ocean warming and changes in net primary production in the 21stcentury will alter community structure of marine organisms, reduce global marine animal biomass and the maximum potential catches of fish stocks with regional differences in the direction and magnitude of changes. Structure and functions of all types of coastal ecosystems will face high to very high risk under RCP8.5 by 2100. Moreover, projected decrease in flux of organic carbon from the surface ocean will reduce biomass of deep seafloor ecosystems. In addition, multiple hazards of warming, deoxygenation and aragonite under-saturation will exacerbate the bioerosion and dissolution of the non-living component of cold-water coral. These selected findings from SROCC highlight the major climate impacts and risks in marine ecosystems, and the scope and limits for their adaptations. They inform the urgency of climate mitigation and adaptation to avoid or minimize impacts on sensitive marine ecosystems.
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