Scampi fishing in North Sea driving ‘invisible’ climate cost, scientists say

Scampi fishing in the North Sea is driving a “largely invisible” climate cost by disturbing carbon that has been buried in seabeds for thousands of years, scientists have found.

Research led by the University of Exeter examined carbon in the Fladen Ground – a large muddy seabed east of Scotland, which is one of the North Sea’s most commercially important fishing grounds.

Here, crustaceans including Norway lobster (or scampi) are caught by bottom trawling, a fishing method where nets are dragged across sea floor habitats, indiscriminately scooping up species.

Fladen Ground is located on a continental shelf, where seabed muds are important long-term stores for carbon, helping to regulate the global climate.

But these muds vary in how much carbon they store, how quickly they bury it, and how vulnerable that carbon is to being released into the ocean-air system, the researchers say.

The study, which is part of the five-year global research programme Convex Seascape Survey, found the Fladen Ground builds up new carbon very slowly.

This means much of the carbon it contains was deposited as far back as the last ice age.

After bottom trawling churns up the sediment, new carbon levels do not replenish quickly enough and therefore the ancient stores are likely affected, the researchers said.

They also found that as disturbed material floats back down to the seabed in Fladen Ground, there is less carbon compared to other areas of muddy seabeds, which can build up new carbon faster.

The severity of bottom trawling’s climate impact therefore depends on where it occurs, with disturbance having different impacts on carbon in different muds, the findings suggest.

While scampi is often marketed as a sustainable seafood choice, Zoe Roseby, lead author of the study, said: “Many people don’t realise that Norway lobsters live in mud, or that catching them involves towing nets directly across the seabed.

“That makes the environmental cost of scampi largely invisible to consumers.”

On different muds, Ms Roseby said: “Some areas of the seabed are still actively accumulating sediment and carbon today, whereas the Fladen Ground is a low-accumulation environment.

“Most of the carbon stored there was deposited at the end of the last ice age and is not being replenished in our lifetime.

“This means that modern trawl events can disturb sediments and carbon deposited several thousand years ago.”

The Fladen Ground is not even necessarily the most climate sensitive place to trawl, she said.

“As it accumulates carbon so slowly and contains relatively refractory material, disturbing it may mobilise less reactive carbon than in other areas with carbon-rich muds.

“The broader message is that not all seabeds carry the same climate risk.”

The study argues effective marine management should consider not only how much carbon is stored in seabed sediments, but how quickly it is being buried and how vulnerable it is to being released.

Callum Roberts, co-author of the study and lead scientist of the Convex Seascape Survey, said: “For fisheries to be genuinely sustainable, we have to consider where fishing takes place and how different seabed habitats function in the carbon cycle.

“This isn’t an argument against eating scampi or against fishing itself.

“But if seafood is to be climate-smart, we need to think not just about what we catch, but how and where we catch it, and use smarter spatial management to avoid disturbing seabeds that are actively accumulating and efficiently burying more vulnerable carbon.”

The research, published in the journal of Marine Geology, comes as part of the collaboration between Blue Marine Foundation, the University of Exeter and Convex Group insurance company, which aims to build understanding of the ocean and its continental shelves in the Earth’s carbon cycle.