EXCLUSIVE: Scientists as “honest brokers” in the bottom trawling and carbon debate

The relationship between bottom trawling and carbon has become an increasingly important area of research, with recent studies suggesting that up to 370 million tonnes of C02 may be released into the atmosphere as a direct result of bottom trawling.

Yet, for Jan Geert Hiddink, Professor of Marine Ecology at Bangor University, previous work has presented an overly simplified picture.

The SeaSTORE project, which Hiddink leads, is now moving into its analysis stage following the completion of its second research cruise on 15 August.

The work has followed collaboration with the fishing industry, with researchers working alongside bottom trawlers and one beam trawler to investigate the direct impact of trawling under contrasting environmental conditions, a factor Hiddink argues had not been sufficiently accounted for in initial studies.

“They assume that the impact of trawling on carbon in [the] seabed is the same everywhere and that’s very unlikely to be true because, well, the carbon content in sediment differs quite a lot.”

Understanding the context

For Hiddink, understanding the relationship between bottom trawling and carbon requires looking beyond the act of trawling itself and considering the environmental conditions in which it takes place.

As part of the SeaSTORE programme, researchers have deliberately sampled different environments to examine how factors including sediment type, water movement and stratification can influence the fate of carbon disturbed by fishing.

“We have specifically designed [our research] to try and capture the effects of different environmental conditions so we have been looking in four different areas,” Hiddink explains, “These four different areas were selected because we expect them to have different sensitivities to bottom trawling”.

Dr Emma Cavan also highlighted how the practical aspects of SeaSTORE differed from previous research. The large size of the research ship, for example, meant “we were then able to take a big team of scientists on board”, bringing together researchers from a range of disciplines.

This breadth of expertise, brought together from different universities and research centres, allowed the project to approach the question from multiple perspectives, from sediment science to Cavan’s focus on the water column.

For the researchers, bringing these different areas of expertise together is key to developing a more complete picture of what happens to carbon when the seabed is disturbed.

As Cavan states, “there’s a lot of processes that happen and it’s not simple enough to just say bottom trawling means sediment goes into the water and all that carbon ends up in the atmosphere.”

Scientists as “honest brokers”

For Hiddink, this need for a more detailed understanding also informs the role of scientists in discussions around fisheries management.

The SeaSTORE project aims to put together an ecosystem model to evaluate “what is going to be effective” in reducing carbon impacts. This process will involve stakeholders from the fishing industry, government and environmental organisations in discussions about which management options should be explored.

The aim, Hiddink says, is to ensure that the research examines options that are both relevant and realistic.

“It’s important for the scientists to show that they’re like honest brokers in these situations,” he says, emphasising the importance of objectively conducting and reporting the science.

For a project examining an issue with significant implications for fisheries management, Hiddink says maintaining that distinction between scientific research and advocacy is important.

He argues that the research could help inform more targeted management options, rather than blanket approaches. Any recommendations would be more nuanced, considering “where and when and what fishing gears you shouldn’t fish with if you want to minimise those environmental impacts.”

The researchers are not envisioning outcomes that “say we should stop all fishing with this particular gear”, but rather approaches that are more specific to location and season, reflecting Hiddink’s view that environmental impacts need to be considered alongside the continued need for fishing.

The team is also aware that measures designed to reduce one environmental impact could potentially just displace impacts elsewhere.

“Fishing does have negative effects on seabed, but so do all the food production methods,” Hiddink says. “Blanket bans are just going to displace problems to somewhere else, and that somewhere else may increase environmental impacts rather than decrease it.”

Collaboration with the fishing industry

The involvement of the fishing industry has also been central to the practical side of the research. Some elements of the research could not be carried out without working directly with fishers, while their knowledge has helped researchers understand how the research could be made relevant to real-world fishing activity.

For Cavan’s team, this brought a new set of logistical challenges. She explained that researchers had to adapt their plans depending on where the vessels were fishing and when they were able to operate, rather than simply following a predetermined research schedule.

“We had to be much more willing to be dynamic and flexible, depending on where they were fishing and what hours they were able to fish,” Cavan says. This could mean periods of intensive work, with researchers working for 24 or 48 hours continuously to capture a trawl before waiting for fishing activity to begin again.

For Hiddink, this relationship with the industry builds on a longer history of collaboration at Bangor University. He says there are aspects of fisheries research that “you can’t do without the fishing industry”, particularly when research needs to reflect how fishing actually takes place.

What comes next

With SeaSTORE around halfway through its four-year programme, the researchers are yet to reach the final stage of understanding what happens to carbon after the seabed is disturbed.

The next phase will involve analysing samples collected from the sediment and water column, including laboratory work examining how readily carbon is broken down. The researchers will also analyse the role of seabed organisms and bring together the data collected across the different environments. This information will ultimately feed into an ecosystem model designed to examine the wider implications of bottom-trawling impacts and evaluate potential management options.

For Cavan, this modelling is particularly important because the team can only directly observe what happens to carbon for a limited period after it is disturbed. Some carbon may remain dissolved in the water, moving with currents or be taken up through biological processes, making it impossible to follow every pathway directly.

Cavan describes how in tracking the carbon “you can’t follow all the molecules and the carbon particles so that’s when we use computer simulations and computer models”.

The model will therefore help the researchers trace these processes beyond what can be observed during a research cruise, bringing together the different environmental conditions and carbon pathways examined by the project.

There is still more than two years of SeaSTORE’s programme remaining. For now, the researchers’ focus is on turning the extensive fieldwork and laboratory measurements into the evidence needed to understand what is happening beyond the seabed.