By Eamonn Ryan, from the webcast
The CSIR study, led by Dr Tommy Ryan-Keogh, reveals that climate models have underestimated the decline, threatening global ecosystems and food security. This is Part 1 of a five-part series on the urgent need for better climate models to secure global ecosystems and food security.
The CSIR’s recent groundbreaking study, led by Dr Tommy Ryan-Keogh, sheds light on a critical issue that extends far beyond environmental concerns—one that directly impacts the global cold chain, particularly in South Africa. As ocean productivity continues to decline due to climate change, the implications for marine ecosystems are profound. This decline threatens the stability of food security systems, as fisheries—a key aspect of the cold chain in food production—may face increased volatility. Given South Africa’s dependence on fisheries and its strategic position within the global cold chain network, the study’s findings serve as a stark reminder of the interconnectedness between ocean health and food supply systems.
Dr. Ryan-Keogh, along with his co-authors Dr. Sana Tamala of CSIR and Professor Alessandra Todd Bui of the University of Liverpool, discussed their findings, which were recently published in Nature’s Communications Earth & Environment. The study analysed satellite data spanning 26 years (1998-2023) and found a 7-10% decline in ocean primary production, a key factor in maintaining the planet’s carbon balance and supporting marine ecosystems such as fisheries. However, the study found that climate models, even the most advanced ones, have not accurately captured this decline.
The uncertainty of climate projections
One of the key findings of the study is that despite projections from 15 different climate models, the impact on ocean productivity by the end of the century remains uncertain. Some models suggest productivity will increase, while others predict a decline. However, when the models are averaged, the projected changes seem negligible, masking the uncertainty in future projections. Dr Ryan-Keogh emphasised that this uncertainty poses a significant challenge to understanding how marine ecosystems, particularly fisheries, will evolve under future climate conditions.
Ocean primary production, primarily driven by phytoplankton, plays a crucial role in the global carbon cycle. Phytoplankton absorbs CO2, and any significant changes in their population due to warming oceans could have far-reaching consequences. A decline in ocean productivity would not only affect marine biodiversity but would also disrupt the food chain, threatening the livelihoods of the more than three billion people who rely on seafood as their primary protein source.
Satellite data illuminates the decline
To address the gaps in climate models, the team turned to satellite data, which has provided a more accurate picture of the current state of ocean productivity. Using six different algorithms, they tracked annual trends over the past 26 years and found consistent evidence of declining primary production, particularly in areas marked in red on the maps. These satellite data products have provided more reliable evidence of the adverse impacts of rising sea temperatures on ocean productivity.