Bottom trawling, a destructive fishing method, is now recognised as a major contributor to climate change and ocean acidification. By disturbing seafloor sediments, this practice releases significant amounts of stored CO2 into the atmosphere—comparable to 9-11% of global land-use change emissions in 2020 alone. The rapid release of carbon accelerates atmospheric CO2 levels while worsening ocean acidification, posing serious threats to marine ecosystems and biodiversity. As researchers highlight the urgency for action, reducing bottom trawling could play a critical role in combating climate change and safeguarding vital carbon reservoirs beneath our oceans
A new study has brought to light the significant environmental impact of bottom trawling, a prevalent fishing method that involves dragging heavy gear across the seafloor. While this practice has long been criticized for its destructive effects on marine habitats, recent research reveals that it also plays a substantial role in accelerating climate change and ocean acidification. Conducted by an international team of scientists, the study found that bottom trawling releases alarming amounts of stored CO2 from marine sediments, contributing significantly to atmospheric CO2 levels.
The researchers employed a multifaceted approach to assess the impact of bottom trawling. They utilized satellite data from Global Fishing Watch to gauge the intensity and extent of trawling activities, analyzed sediment carbon stock estimates from previous studies, and ran carbon cycle models to simulate the transport and fate of trawling-induced CO2 over time. Their findings are startling: between 1996 and 2020, trawling activities are estimated to have released 8.5-9.2 petagrams (Pg) of CO2 into the atmosphere, equating to an annual emission comparable to 9-11% of global emissions from land-use change in 2020 alone.
One of the most striking revelations is the rapid rate at which CO2 released by trawling enters the atmosphere. The study found that 55-60% of this CO2 is transferred from the ocean to the atmosphere within just 7-9 years, while the remaining 40-45% stays dissolved in seawater, contributing to ocean acidification. The carbon cycle models further revealed that even regions without intense trawling, such as the South China Sea and Norwegian Sea, could be affected by CO2 transported from other areas.
The findings suggest that reducing bottom trawling efforts could serve as an effective climate mitigation strategy. Given that the atmospheric CO2 effects of trawling are relatively short-lived compared to other carbon sources, implementing policies to limit trawling could lead to significant reductions in emissions. The study underscores the importance of protecting marine sediments, not only for biodiversity but also for their critical role in regulating our climate by storing vast amounts of carbon.
Summary By: Aeneas Koosis | Original Study By: Atwood, T.B., Romanou, A., DeVries, T., Lerner, P.E., Mayorga, J.S., Bradley, D., Cabral, R.B., Schmidt, G.A., & Sala, E. (2024) | Published: July 23, 2024
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A new study reveals that bottom trawling, a common fishing practice, releases substantial amounts of CO2 from marine sediments, potentially accelerating climate change and ocean acidification.
Bottom trawling, a fishing method that involves dragging heavy gear across the seafloor, has long been criticized for its destructive impact on marine habitats. This study found that this practice also has significant implications for our climate. The research, conducted by an international team of scientists, found that bottom trawling releases alarming amounts of stored CO2 from marine sediments, contributing to atmospheric CO2 levels and ocean acidification.
The researchers used a combination of methods to investigate the impact of bottom trawling. They examined satellite data from Global Fishing Watch to estimate the intensity and extent of bottom trawling. They also analyzed sediment carbon stock estimates from a previous study. Finally, they ran carbon cycle models to simulate the transport and fate of trawling-induced CO2 release over time.
They found that between 1996 and 2020, trawling activities are estimated to have released a staggering 8.5-9.2 Pg (petagrams) of CO2 into the atmosphere. This equates to an annual emission of 0.34-0.37 Pg CO2, which is comparable to 9-11% of global emissions from land-use change in 2020 alone.
One of the most striking findings is the rapid pace at which trawling-induced CO2 enters the atmosphere. The study found that 55-60% of the CO2 released by trawling is transferred from the ocean to the atmosphere within just 7-9 years. The remaining 40-45% of CO2 released by trawling stays dissolved in seawater, contributing to ocean acidification.
The carbon cycle models allowed the team to track the movement of CO2 through ocean currents, biological processes, and air-sea gas exchange. This revealed that even areas without intense trawling, such as the South China Sea and Norwegian Sea, could be affected by CO2 transported from other regions.
The findings suggest that reducing bottom trawling efforts could be an effective climate mitigation strategy. Because the atmospheric CO2 effects of trawling are relatively short-lived compared to other carbon sources, policies limiting trawling could lead to significant reductions in emissions.
The study emphasizes the importance of protecting marine sediments as critical carbon reservoirs. In addition to their role in supporting biodiversity, marine sediments play a vital role in regulating our climate by storing vast amounts of organic carbon. The authors note that their estimates are likely conservative, as data limitations and knowledge gaps prevented them from fully accounting for the global extent of trawling. They call for further research to refine our understanding of trawling’s impact on sedimentary carbon stocks and the processes driving CO2 release.
The authors strongly recommend that advocates and policymakers prioritize the protection of marine sediments as a critical component of both ocean conservation and climate change mitigation efforts. By working together to reduce destructive fishing practices like bottom trawling, we can safeguard the life in our oceans while also helping to secure a more stable climate for future generations.
Meet the Author: Aeneas Koosis
Aeneas Koosis is a food scientist and community nutrition advocate, holding degrees in Dairy Chemistry and Plant Protein Chemistry. He is currently working towards a PhD in Nutrition, concentrating on enhancing public health through meaningful improvements in grocery store design and practices.
Citations:
Atwood, T.B., Romanou, A., DeVries, T., Lerner, P.E., Mayorga, J.S., Bradley, D., Cabral, R.B., Schmidt, G.A., & Sala, E. (2024). Atmospheric CO2 emissions and ocean acidification from bottom-trawling. Frontiers in Marine Science, 10, 1125137. https://doi.org/10.3389/fmars.2023.1125137
Notice: This content was initially published on Faunalytics.org and may not necessarily reflect the views of the Humane Foundation.
