Research in support of designing strategies to manage the effects of climate change on fisheries and coastal areas. A study about the future of ocean net primary production published with the contribution of the CMCC Foundation.

Ocean net primary production, the fixation of  CO₂  by marine phytoplankton, is the primary source of  organic compounds and energy transfer to marine ecosystems. It is at the origin of marine life and provides livelihood to its ecosystems, supports the marine food webs and, consequently, fisheries production.

Climate change, by affecting various elements of the Earth system – from atmospheric circulation to marine physics, including sea water temperature – is expected to have impacts on ocean primary production. And alterations to primary production will have consequences and costs for all the marine ecosystem services that it supports.

The study “Persistent uncertainties in ocean net primary production“, released with the participation of the CMCC Foundation, highlights an uncertainty that represents a warning signal for climate change adaptation strategies, since it makes it hard for the world of research to provide clear information on ocean primary production to be used by decision makers to build policies to adapt to climate change. An uncertainty that does not characterize other indicators related to climate change, such as global warming or ocean acidification.

So far, the scientific literature suggested that there would be a global reduction in ocean net primary production for the next few decades, although considerable uncertainty was observed, as highlighted by the differences in the results of different models used.

“Prior to this study, although the scientific community agreed on the need to reduce the existing uncertainty on the topic, there seemed to be at least a consensus on the sign of the expected change: most of the models under investigation indicated a decrease in ocean net primary production in the future,” explains Momme Butenschön, a researcher at the CMCC Foundation among the authors of the research. “As this study shows, instead, we can no longer be so confident about it.”

Previous literature on the topic, including that on which the IPCC Special Report “Ocean and Cryosphere in a Changing Climate” (2019) relies, uses outputs from the Coupled Model Intercomparison Project (CMIP5 – Phase 5). Instead, this study uses its evolution (CMIP6), which uses higher resolution models and allows for better representation of small-scale processes. CMIP6 also includes some processes that previously were not present or not explored in depth, such as biological nitrogen fixation or remineralization of nutrients by planktonic bacteria.

The implications of such significant uncertainty in the future of marine primary production are diverse and considerable, and have economic implications as well.

The marine fisheries sector cannot adequately adapt, since it does not know whether the resources available to fish are projected to increase or decrease in the coming decades. Moreover, uncertainty is greater at a regional scale, most notably in certain areas, such as the Tropical Pacific and Indian Ocean, where the fisheries sector plays a significant role in local economies and global food supplies, with implications for local fisheries management.

Alessandro Tagliabue, lead author of the study, said “it was surprising to see the level of disagreement across models, even for the current era. These uncertainties in the projected changes in net primary production are particularly pronounced at the regional scales that are crucial for management of fisheries and other resources. Particular regions of concern include the North Atlantic and the Indo-Pacific regions, with important implications for dependent communities.”

Uncertainty about the effects of climate change on ocean net primary production also limits long-term planning for a better management of other ecosystem services, such as coastal habitats. Moreover, due to uncertainty in the ability to absorb CO₂ through the biological carbon pump, it will have implications in terms of estimation of climate change mitigation costs.

For more information:

Tagliabue A, Kwiatkowski L, Bopp L, Butenschön M, Cheung W, Lengaigne M and Vialard J (2021) Persistent Uncertainties in Ocean Net Primary Production Climate Change Projections at Regional Scales Raise Challenges for Assessing Impacts on Ecosystem Services. Front. Clim. 3:738224. doi: 10.3389/fclim.2021.738224