Net Losses: Study Reveals More Trouble With Trawling

A groundbreaking study published in the journal Frontiers in Marine Science has unveiled more damning data about the environmental consequences of bottom trawling—a common commercial fishing practice used worldwide.


Carbon Footprints On The Seafloor

Bottom trawling involves the use of large, weighted nets—up to half a mile in length—that scour the ocean floor to capture seafood like shrimp, crab, halibut and cod. Scientists have long denounced bottom trawling for the damage it does to otherwise healthy seabed ecosystems—razing coral reefs fatally tangling non-targeted species in the drag nets. 

But the ecological toll extends far beyond the visible scars, as scientists have uncovered disturbing new data—the practice of bottom trawling is responsible for the release of up to 370 million metric tons of CO2 annually. This figure is more than double the emissions from the global fishing industry's fossil fuel consumption, casting a shadow over the sustainability of the seafood on our plates.

Ocean Acidification

As CO2 released from disturbed seabed sediments mingles with the ocean waters, another threat emerges. The increase in CO2 content of the water from trawling causes the slow dissolution of marine organisms’ protective calcium carbonate shells, a process that is only exacerbated by increasing amounts of CO2 emissions. This could have far-reaching impacts on some of the most popular varieties of shelled seafood, like crabs and mussels.


CO2: From Seabed To Sky

Although dissolved CO2 is naturally gradually released from seabed sediments over time, eventually returning to the atmosphere, bottom trawling expedites this process.

"It only takes about nine years for [carbon dioxide] to make it completely out of the ocean and into the atmosphere, and there’s enough CO2 that is being emitted by global trawling each year that people need to pay attention to it,” said the study’s lead author and associate professor of watershed sciences, Tricia Atwood, "Some of the CO2 is very, very old and might have been laid down in the ocean 10,000 years ago.”

The Toll Of Trawling 

It’s also very possible that the true depth of the impact of bottom trawling has yet to be unearthed. Scientists identified the Baltic Sea, the East China Sea, the Greenland Sea and the North Sea as the most impacted, although data wasn’t available for other under-monitored regions of the world.

The published data still makes a strong case for the need for more decisive action in creating sustainable fishing practices. These numbers demonstrate that around half of the emissions from bottom trawling activities pollute the atmosphere while the other half increases the acidity of the ocean, both causing long-term implications for the climate. 


Turning The Tide On Trawling

Although the release of atmospheric CO2 from trawling is still relatively a small figure in the context of global emissions, its carbon footprint is growing. 

"As humanity expands trawling activities and intensifies them, we expect to see larger regions being affected.” states Anastasia Romanou, co-author of the study and contributing author to the IPCC

The good news is that we can curb the severity of the situation. According to Romanou, thanks to the speed at which CO2 from trawling reaches the atmosphere, "Any mitigation effort will be very effective and we’ll be able to see the results.” 

As coastal civilizations around the world navigate environmental challenges, bottom trawling is just one of many sobering reality checks that reveal the state of our ocean—and planet’s—health. As stewards of the ocean, it is our responsibility to heed the findings of these studies and safeguard the delicate balance of marine ecosystems.