HOW BOTTOM TRAWLING HURTS OCEAN LIFE AND SPEEDS UP CLIMATE CHANGE

When Bryce Stewart dived after the toothed, steel-weighted nets of a scallop dredger rumbling over the bottom of the Irish Sea 22 years ago, he witnessed destruction he could never have seen from a boat.

"Half crabs. Smashed up sea urchins. Starfish missing some of their arms," said Stewart, a marine ecologist at the University of York. "There was literally a trail of dead and dying things on the seabed."

Bottom trawling – a powerful practice in which heavy nets are dragged along the ocean floor to catch fish and seafood – is one of the most harmful ways to feed the world. It destroys ecosystems and sweeps up unwanted marine life that gets thrown overboard. Between 1950 and 2014, bottom trawlers discarded $560 billion of bycatch, which was more than the value of all catches from longline fishers over the same period.

Now scientists fear another environmental disaster bubbling under the surface: climate change.

Trawlers churning 1.3% of the global sea floor stir up more carbon dioxide than the emissions of the entire aviation industry, a study published in the journal Nature last year found. Even if only some of that makes it to the surface, the practice stops seas absorbing as much CO2 from the atmosphere and prevents plant life growing.

Trawling oceans is like digging up a garden again and again, said Stewart, comparing the nets to a plough. "If you're constantly disturbing the seabed, then you have to basically keep restarting that process of storing carbon."

Consumers in Europe can check labels on seafood products to see how it was caught