CSIR researchers say climate models point to a decline in ocean productivity.
Researchers used an analysis of 26 years of remote sensing data, comparing contemporary trends to future projections from a wide range of climate models.
Their study was published in Nature’s scientific journal Communications Earth & Environment on 1 February 2025.
CSIR principal researcher Dr Tommy Ryan-Keogh led the study along with CSIR chief researcher Dr Sandy Thomalla, in collaboration with Professor Alessandro Tagliabue from the University of Liverpool.
Dr Ryan-Keogh said “this is one of the first studies to use data from the past 26 years to assess how ocean productivity may be changing and to link these current changes to the future state of our ocean’s. To predict the anticipated changes, the researchers developed a model ranking scheme that assessed how well each model can represent the relationships between productivity and different environmental drivers. The models which best represented these relationships and are ranked highest all predict future declines in ocean productivity. Nonetheless, the future projections of even the best ranked models are underestimated and much smaller than the changes that researchers are observing now.”
He also said he believes that even the best-ranking models are underestimating the sensitivity of declines in productivity to ocean warming.
Ocean productivity is one of the most critical processes on the planet, because it helps to regulate global climate and supports essential ecosystem services (such as fisheries).
Phytoplankton are microscopic plants that live in the sunlit surface of the waters of the ocean and drive the ocean productivity. However, despite the importance of phytoplankton, scientists do not have a clear understanding of how climate change can impact them.
In this study the researchers argue that the next generation of climate models will need to correct this sensitivity to represent the ongoing changes in ocean productivity accurately. This means that these models will project even greater declines, even under high-mitigation scenarios that currently predict relatively stable ocean productivity at the end of the century.
Dr Thomalla, said “it is important to note, however, that ocean productivity is not declining everywhere. The ocean is patchy, and there are some areas where productivity is increasing, but when we average it across the global ocean, it is decreasing. If we zoom in on the African coastline, for example, we can see large declining trends in ocean productivity inshore, relative to the smaller increasing trends seen in open ocean waters further offshore.”
The role of phytoplankton in the sustainability of our planet is receiving increasing attention, with the “The Plankton Manifesto” launched in 2024.
Phytoplankton are under threat, and this manifesto calls for immediate global recognition and an action plan to protect them.
The Plankton Manifesto is the result of a collaborative effort led by the United Nations Global Compact that involved 30 international experts from leading institutions and industries worldwide. It will seek endorsements at key global environmental conferences, including COP29 on Climate Change, COP16 on Biodiversity, and the United Nations Ocean Conference in Nice, France, in June 2025.
Dr Thomalla also said “this study is a call to attention. Our climate models are currently underestimating the future change in ocean productivity. These global declines will have ramifications for the ocean carbon cycle and marine ecosystems, affecting the trophic system that underpins biodiversity, fisheries and the marine resources on which humans rely.”