The Hidden Climate Impact of Bottom Trawling

As a scuba diver, I’ve seen the wonders of the undersea world—brilliant coral reefs, swaying seagrass meadows, and the incredible creatures that call these places home. That’s why what happens with bottom trawling feels so devastating.

Picture this: a huge fishing boat drags a massive, weighted net across the seafloor. It tears through everything in its path, scooping up fish. At the same time, it crushes coral reefs, seagrass meadows, and habitats that have taken centuries to grow. Behind it, clouds of dark mud swirl like an underwater storm. Even stingrays and baby sharks get trapped, with no chance of escape.

This method, called bottom trawling, is one of the most destructive ways to fish. Alarmingly, it supplies nearly a quarter of the world’s seafood. But that “catch” comes at a steep cost. Bottom trawling destroys delicate ecosystems and kills untargeted animals too—including corals, young fish, sea turtles, whales, and dolphins.

As if that weren’t bad enough, scientists now say bottom trawling may also be fueling climate change.

The Ocean as a Carbon Vault

The ocean is Earth’s biggest “carbon sink,” which means it soaks up carbon dioxide from the atmosphere and stores it away. Tiny plants called phytoplankton float near the surface, pulling in CO₂ during photosynthesis. When they die, many sink to the bottom. Over thousands of years, seafloor sediments bury their remains and lock the carbon in place—like putting it in a vault.

But bottom trawling unlocks that vault. When nets tear across the seafloor, they stir up carbon-rich mud that’s been stored for centuries. Once this mud mixes with oxygen in the water, microbes break it down, turning some of the buried carbon back into CO₂. That CO₂ can then escape into the atmosphere, adding to the greenhouse gases that warm our planet. Some of the carbon also dissolves into the ocean, worsening ocean acidification, which makes it harder for marine life like oysters, clams, sea urchins, and corals to survive.

The Climate Impact

So how big of a deal is this? Scientists are still working it out, but the numbers are definitely worrying. A team of researchers, led by ecologist Trisha Atwood, found that more than half of the carbon stirred up by bottom trawling eventually makes it into the atmosphere. Researchers calculate that trawling pumps 340 to 370 million metric tons of CO₂ into the air each year. To put that in perspective, that’s more than the annual emissions of countries like Italy or Spain. And get this–the carbon stirred up by trawling could pump out as much CO₂ as the entire airline industry if it all escaped into the atmosphere.

David Scaro, a former Alaskan trawler said, “I’ve seen first hand what it is, and it’s not good. The deal with trawling is it’s very industrial, it’s a volume fishery — we are scooping up everything we can, for a low quality product, but if there’s enough of it we can make money”. It not only devastates ocean habitats, but it may also be quietly supercharging climate change.

The takeaway? What happens under the sea doesn’t stay there. The choices we make about how we fish can affect our precious marine life but also the stable climate we need to survive and thrive.

If you like this blog, you might also appreciate Beneath the Surface: Hidden Risks of a Warmer World.