Fishing and Climate Change: What Are the Impacts on Carbon Sequestration in the Ocean?
An An international team led by researchers from the University of Montpellier, the CNRS, the World Maritime University (WMU), and the University of California has quantified the past, present, and future impact of fishing and climate change on the ability of commercially important species (fish and other macroinvertebrates) to sequester carbon on the ocean floor. Their findings, published in the journal Nature Communications, show that climate change is projected to reduce carbon sequestration by commercial species by 13.5% by the end of the century. However, the impact of climate change remains much smaller than that of fishing, which has already reduced this sequestration by 47% compared to 1950. This research therefore calls for more sustainable ocean management that takes into account the impact fishing can have on carbon sequestration.
What if marine macrofauna could help capture more carbon?
Nature-based Solutions (NBS) have the advantage of killing two birds with one stone: mitigating climate change while combating biodiversity loss, through the restoration, protection, or improved management of ecosystems such as forests. But as forests burn, the scientific community is gradually turning to the ocean to find new NBS. In their 2021 joint report, experts from the IPCC and IPBES suggest that the way we manage the food resources the ocean provides must evolve to help us combat climate change. But what is the link between a biodiverse ocean, fishing, climate change, and carbon sequestration? These are the questions this new study seeks to answer.
How does marine macrofauna sequester carbon?
The role of fish and macroinvertebrates (macrofauna) is far from negligible, given that they account for 30% of the carbon sequestered by all marine organisms. Their diet, which consists of carbon, is partly stored in their flesh or expelled via fecal pellets. It is when macrofauna produce fecal pellets or die from disease or old age that the carbon contained within them sinks into the ocean depths, simultaneously sequestering the carbon they contain. Thus, the study shows that in 1950, before the combined effects of fishing and climate change emerged, commercially important macrofauna had the capacity to sequester 0.23 billion tons of carbon per year, 90% of which was via fecal pellets.
The historical impact of fishing
Today, this commercially important macrofauna sequesters only 0.12 billion tons of carbon per year—a 47% decrease compared to the 1950s. “Every time fishing reduces the biomass of commercial species by 1%, carbon sequestration decreases by 0.8%,” the study’s authors note. Fishing has a greater impact on carbon sequestration through the sinking of carcasses compared to sequestration through the sinking of fecal pellets. “This is linked to the fact that fishing targets the largest organisms, which are the ones most likely to die of old age.” In addition to the impacts this may have on carbon sequestration, this decrease in the arrival of carcasses on the ocean floor also means a decrease in the arrival of food in the abyss, as carcasses are a delicacy for the organisms living there. “So, we may be starving a whole host of deep-sea organisms that we barely know about,” they conclude.
The Impact of Climate Change: A Vicious Cycle
The more climate change worsens, the lower the carbon sequestration capacity of commercial species will be, which exacerbates global warming. If the Paris Agreement is met (+1.5°C), sequestration will decrease by 4% by 2100, but by as much as 13.5% if temperatures rise by +4.3°C. For every degree of warming, a 2.46% reduction is expected. Thus, fisheries and climate combined could reduce sequestration by 56% by 2100 compared to 1950.
A new natural solution for the climate?
The study quantifies, for the first time, the benefits of restoring fish and macroinvertebrate populations: up to 0.4 billion tons ofCO2 sequestered per year, a potential comparable to that of mangroves. Over several decades, this would amount to 240 billion tons ofCO2, equivalent to six years of human emissions. SNCs linked to the restoration of commercial species populations therefore appear to be a promising avenue, but their contribution to meeting climate goals will remain minimal if these measures are not viewed as complementary to a drastic and immediate reduction in greenhouse gas emissions. The researchers also highlight numerous uncertainties surrounding this new field of research. “For example, the effect of restoring commercial species on their prey, which are also involved in carbon sequestration, remains unknown. While it is difficult to conclude that a new CNS exists, our results nevertheless illustrate the importance of managing the ocean more sustainably to prevent the destruction of a carbon sink whose protection could bring benefits for biodiversity and the climate,” they conclude.
Practical information:
- Publication date: October 27, 2025
- Read the full article here