Trawling for trouble: How fishing along the seafloor significantly worsens climate change

One of the least discussed factors of global heating is trawling the seafloor. It's also one of the easiest to stop

By Matthew Rozsa

Staff Writer

Published January 29, 2024 7:09AM (EST)

Bottom trawler, fishing boat sailing along the North Sea coast silhouetted against orange sunset in front of Nieuwpoort, Flanders, Belgium. (Arterra/Philippe Clément/Universal Images Group via Getty Images)
Bottom trawler, fishing boat sailing along the North Sea coast silhouetted against orange sunset in front of Nieuwpoort, Flanders, Belgium. (Arterra/Philippe Clément/Universal Images Group via Getty Images)

When fishing companies go trawling, an industrial fishing method the involves dragging a fishing net across the seafloor, they wreak havoc on the lives of countless ocean creatures. These heavily-weighted nets can severely disrupt the delicate ecosystems deep beneath the waves. Furthermore, trawling doesn't discriminate, frequently scooping up aquatic life that is unmarketable, or sometimes even illegal to fish, right along with any desired catch. All of this has evident since the practice began in the 14th century — but what has been less well-known is the other impacts trawling, especially climate change.

"Our findings emphasize the need for policy to avoid exclusive focus on avoided atmospheric emissions."

Now a recent study in the journal Frontiers in Marine Science sheds light on this murky subject, while presenting some sobering data: Between 55% and 60% of trawling-induced aqueous CO2 has been released into the atmosphere over the past seven to nine years. The authors estimate that, between 1996 and 2020, trawling could have released around 340 billion kilograms (750 billion pounds) of CO2 to the atmosphere all over the planet.

That said, there is some good news here. The fundamental challenge in fighting climate change involves reducing humanity's emission of greenhouse gases into the atmosphere, which will in turn cause the planet to stop overheating. When it comes to symptoms of climate change like sea level rise and shifting seasonal times, they are baked into humanity's future; even if we altered all of our behaviors for the better today, we still face these outcomes. They will be far worse if we do nothing at all — the best we can do at this point is try to prevent the damage from getting worse — but world leadership has collectively ignored too many milestones when it comes to stopping some aspects of a changed climate.

Yet if the human species was willing to put an immediate stop to trawling tomorrow, doing so could instantly take a large bite out of our carbon emissions problem.

"The rapid release of CO2 from the ocean to the atmosphere suggests that historical trawling has only short-term legacy effects on atmospheric emissions," the authors explain. "Thus, policies that eliminate or significantly limit trawling impacts on sedimentary carbon stocks would quickly reduce this industry’s contribution to rising atmospheric CO2 concentrations with maximum benefits occurring 7-9 years after implementation."

The authors argue that the information gleaned from their study could be invaluable to future scientists "for evaluating the reduction of bottom trawling effort as an effective ocean-based climate solution." That said, they argued that further research will need to be performed to fill in the knowledge gaps regarding how bottom trawling specifically interferes with the process that lead to carbon remineralization and preservation. Scientists will also need to develop more sophisticated models for estimating emissions in specific areas. Yet there is one undeniable conclusion from their research: When it comes to limiting greenhouse gas emissions, activists should not only be looking at the air.

"Our findings emphasize the need for policy to avoid exclusive focus on avoided atmospheric emissions, as our results show that trawling-induced increases in DIC [dissolved inorganic carbon] in seawater could have severe implications for local or regional ocean acidification," the authors point out.

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"Historical trawling has only short-term legacy effects on atmospheric emissions."

Other recent scientific research has also connected climate change to trawling in the fishing industry. In a May study in the journal Nature, the authors argued that previous estimates of the CO2 being released through trawling had been overestimated "by several orders of magnitude" due to a number of alleged errors in their methodology. Their conclusion was that "we currently do not know enough about the impact of trawling on seabed carbon to make robust global projections."

By contrast that original 2021 study in the journal Nature — which offered the initial estimates about carbon released from trawling — did so as part of a larger warning about the need to protect Earth's oceans.

"We find that a substantial increase in ocean protection could have triple benefits, by protecting biodiversity, boosting the yield of fisheries and securing marine carbon stocks that are at risk from human activities," the authors argued. "Our results show that most coastal nations contain priority areas that can contribute substantially to achieving these three objectives of biodiversity protection, food provision and carbon storage."

An analysis by The Guardian also found that the study's estimate for the amount of carbon dioxide emitted — namely, between 0.6 and 1.5 gigatons of carbon dioxide a year, amounting to an average of 1 gigaton annually — was equivalent to aviation emissions of carbon dioxide in 2019, which equalled 918m tons.

There are links between the fishing industry and climate change in ways that go far beyond the practice of trawling. Plastic pollution is a persistent problem, with a trash island known as the North Pacific garbage patch taking up more than 610,000 square miles (1.7 million square kilometers), making it approximately twice the size of Texas. The North Pacific garbage patch is only a grotesque symptom of the larger problem, as plastics large and small covering the Earth. Much of these plastics come from the fishing industry, with Greenpeace estimating that nets, lines, traps, pots and other abandoned or lost gear from commercial fishing makes up the majority of large plastic pollution in the ocean. A 2022 study in the journal Scientific Reports concluded that "most floating plastics in the North Pacific subtropical gyre can be traced back to five industrialised fishing nations, highlighting the important role the fishing industry plays in the solution to this global issue." On-the-ground workers fighting plastic pollution by disentangling seals estimated to Salon that roughly 70 percent of the debris they encounter is in some way linked to commercial fishing.

As these synthetic plastic molecules are produced — even when we have plenty of viable alternatives — they are disposed of and continue to accumulate indefinitely. Through this process, they pour a massive amount of greenhouse gases into the atmosphere: After all, they are originally derived from fossil fuels. As a result, the UN Environment Programme estimates that the problem of plastic pollution — from the moment a product is made to when it is ultimately discarded — overall accounts for 19 percent of the total global carbon budget by 2040.

Climate change is also expected to adversely impact the fishing industry itself. According to a 2020 report in the journal Marine Policy, climate change is likely to cause conflict within the fishing industry as the changing environment harms the business in innumerable ways. The fish stocks on which the industry relies will become less productive and change their distribution, while coastal infrastructure will be damaged by the intensified elements, to name just two of the serious issues with which fishers' will have to grapple as climate change worsens. Indeed, the industry is currently so under-regulated that fish fraud — or the practice of mislabeling the fish sold to consumers, so that they are not eating the type of fish they intended to purchased —remains prevalent.

By Matthew Rozsa

Matthew Rozsa is a staff writer at Salon. He received a Master's Degree in History from Rutgers-Newark in 2012 and was awarded a science journalism fellowship from the Metcalf Institute in 2022.

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