What is bottom trawling? Bottom trawling is an industrial fishing method where a huge net with heavy weights is dragged along the sea bed, scooping up everything in its path. Huge is something of an understatement. As ‘Seaspiracy’ says, “the largest trawl nets are so big that they can swallow whole cathedrals or up to thirteen jumbo jets.” How does bottom trawling contribute to global warming? This year saw the publishing of the first-ever study to calculate the carbon cost of bottom trawling. ‘Protecting the global ocean for biodiversity, food and climate’ found that bottom trawling releases as much CO2 as the entire aviation industry.