Trawling releases tons of CO2, says study – 01/19/2024 – Environment

Ocean bottom trawling is releasing tons of carbon dioxide (CO_two), according to scientists who quantified for the first time the greenhouse gas emissions caused by this destructive fishing technique.

Trawling vessels use huge, heavy nets — up to 800 meters long — that scour the ocean floor to capture shrimp, crabs, cod, flounder and other fish. Scientists and environmentalists have long opposed bottom trawling because of the damage it causes to seabed ecosystems such as coral reefs, and the deaths of sea turtles, sharks and other marine species that are accidentally caught in the bottom. networks.

There is also a climate cost, according to an article published this Thursday (18) in the journal Frontiers in Marine Science. Researchers calculated that the disturbance of CO_{twostored in seabed sediments by trawling releases up to 370 million tons of this greenhouse gas into the atmosphere each year. This is more than twice the COtwo emitted by the burning of fossil fuels by the global fishing industry.}

The authors of the new paper also estimated that any CO_two released into the ocean is acidifying the waters around it, which can dissolve the shells of crabs, mussels, sea urchins and other seafood that people depend on.

“These are closed areas, especially like the Mediterranean, where we can see that CO_two can create localized acidification that can be quite substantial,” said Trisha Atwood, lead author of the study and associate professor of watershed sciences at Utah State University.

She noted that more research is needed to quantify the local impact of acidification, since the researchers’ modeling looked at the ocean on a global scale.

This study is not the first to link trawling and CO_two: an article published in 2021 in the journal Nature, which analyzed CO measurements_two in trawling areas, established for the first time that disturbed sediments released planet-warming gas into the ocean.

The new research, based on this data, used computer models to show that 55% to 60% of the carbon dioxide released by trawl sediments reaches the atmosphere from depths of at least 500 meters, while the rest remains in the ocean.

Although it can take decades for carbon dioxide dissolved in seafloor sediments to be released into the atmosphere, depending on the depth, scientists’ models have shown that CO_two from trawling quickly came online between 1996 and 2020.

“It only takes about nine years for it to completely leave the ocean and enter the atmosphere, and the amount of CO_two being emitted by global trawl fisheries each year is enough that people should pay attention to this issue,” Atwood said. “A portion of this CO_two It’s very, very old and may have been deposited in the ocean 10,000 years ago.”

Anastasia Romanou, a NASA scientist who studies the carbon cycle in the ocean and is a co-author of the new paper, said the speed at which CO_two from trawling reaches the atmosphere means that restricting the practice would have an almost immediate climate benefit.

“Any mitigation effort will be very effective and we will be able to see results,” said Romanou, one of the authors of the United Nations Intergovernmental Panel on Climate Change.

Findings still underestimate CO emissions_two from bottom trawling, Atwood said, as data was not available for certain little-monitored fishing spots, such as Southeast Asia. Scientists have identified the Baltic Sea, East China Sea, Greenland Sea and North Sea as most impacted by bottom trawling.

The new research will likely face resistance from some sectors of the scientific world. Following the publication of the 2021 paper, a group of scientists wrote a response questioning the methodology used and arguing that the researchers overestimated the amount of CO_two released by seabed sediments due to trawling.

The 2021 paper’s lead author, marine scientist Enric Sala, said in a statement that the new research validates his colleagues’ initial findings. “Many people have downplayed the importance of the 2021 study’s findings, saying that carbon in the water is inconvenient, but that air emissions are what counts,” said Sala, also a co-author of the new paper and executive director of National’s Pristine Seas initiative. Geographic Society.

“This one [novo] The report is essential as it shows that approximately half of trawling emissions pollute the atmosphere and the other half increase ocean acidity,” he said.

Romanou said that although the estimated release of CO_two atmospheric emissions from trawling is a significant percentage of fishing-associated emissions, it is a small number in the context of total global emissions.

Still, trawling’s footprint is increasing, she noted, and policymakers are not yet considering its impacts on ocean acidification and CO emissions._two. “As humanity expands trawling activities and intensifies them, we expect to see larger regions being affected,” Romanou said.