What is trawler net management, and can it help save our planet?

​​Closer management of bottom-trawling fishing methods could prevent millions of tonnes of carbon dioxide being emitted from the seabed into the atmosphere, a new study shows.

It is already widely known that large trawlers have dredged the bottom of the seabed for decades, disturbing the carbon that has settled there, but new research has revealed the actual impact.

Climate and ocean experts from Frontiers, the research publisher and open science platform have used satellite-inferred fishing events and carbon cycle models to fully understand the effect the enormous heavy fishing nets have on the environment.

The global study “Atmospheric CO2 emissions and ocean acidification from bottom-trawling” found that 55-60 per cent of trawling-induced aqueous CO2 is released into the atmosphere over a seven to nine-year period.

Scientists involved in the study, which ran from 1996-2020, estimated the total carbon dioxide released from trawling to the atmosphere to be 8.5 to 9.2bn tonnes. It highlighted the trawling hotspots as the East China Sea, the Baltic and the North Sea, and the Greenland Sea, where such activity had made the most significant carbon impact.

It is understood large-scale bottom trawling began as early as 1950, before peaking in the 1980s and 1990s. This study used the AIS vessel tracking database processed by Global Fishing Watch to establish global trawling events.

As AIS coverage is poor in some fishing-intensive areas, experts expect trawling activity to be underestimated in areas such as Southeast Asia, the Bay of Bengal, the Arabian Sea, parts of Europe, and the Gulf of Mexico.
The report said: “Our results suggest that the management of bottom-trawling efforts could be an important climate solution.

“The protection of organic carbon stored in marine sediments, plants, and animals has been identified as a powerful tool for tackling climate change.

“However, the uptake of ocean-based climate solutions has been slow due to prevailing climate policies and carbon markets that only recognize mitigation activities with measurable impacts on atmospheric emissions.

“The challenge with identifying ocean-based solutions under those current paradigms lies in the complexity of quantifying atmospheric emissions generated by anthropogenic activities that occur below the ocean’s surface. Therefore, research addressing this challenge is crucial for discovering new opportunities that can harness the full potential of the ocean in contributing to mitigating climate change.”

Tom Townsend, Principal Consultant – Food and Beverage at Acre, said: “We have known for a long time about the damage caused by trawler nets.

“But an in-depth report such as this one from the Frontiers team, enables us to better understand the data surrounding what is happening in the ocean and the steps that must be taken to ensure such vast amounts of carbon do not escape into the atmosphere.

“The report is alarming and, one hopes, could be the catalyst which encourages governments and the industry to reexamine its relationship with our oceans. Only through examining fishing methods and consumption patterns can we begin to tackle our impact on the planet.”