A new global study warns that the climate cost of seabed trawling is still largely unknown, and researchers say urgent action is needed to close the data gap.

The work is part of the Convex Seascape Survey, a five-year ocean carbon research project backed by Bermudian-headquartered speciality reinsurer Convex Group Ltd.

Convex, which operates out of Bermuda and London, has pledged millions to the project and aims to play a major role in climate-related research and resilience financing.

The study, published in the journal Fish and Fisheries, finds a major uncertainty in the effort to understand how bottom-trawling — where fishing nets are dragged along the sea floor — might be releasing vast amounts of stored carbon into the atmosphere. Ocean sediments are the planet’s largest carbon sink, and scientists say human disturbance from trawling may be undermining this vital buffer against climate change.

“To find out how much carbon is being released by these fishing methods, we need to know how much of the seabed is actually being disturbed,” said Mollie Rickwood, a researcher at the University of Exeter and co-author of the paper. “Our main finding is that vessel and gear sizes vary a lot from country to country — so using European data to make global estimates is likely to lead to large inaccuracies.”

The team found a strong European bias in existing data on fishing gear, making global assessments unreliable. “Our paper is a call to arms to address these knowledge gaps and encourage global collaboration between science and industry to make this data available,” Ms Rickwood said.

The research forms part of the Convex Seascape Survey, which is led by the University of Exeter and the Blue Marine Foundation and funded by Convex. The survey is the most ambitious attempt yet to map and understand the role of the seabed in the global carbon cycle, according to Convex.

“Anticipating and mitigating future risks is at the heart of what we do at Convex,” said Stephen Catlin, chairman and chief executive of the reinsurer, in a statement announcing the survey in 2021. “This is a huge opportunity to support cutting-edge and impactful research.”

Professor Callum Roberts, lead scientist on the Convex Seascape Survey, added: “Ocean carbon stores could be more secure than those on land … so it is critical we understand how safe carbon is once it is locked away in the seabed.”