Thursday, October 28

A study estimates the CO₂ released by trawling per year in one billion tons | Climate change | Climate and Environment

Trawls of a fishing boat off the Scottish shores near Edinburgh.
Trawls of a fishing boat off the Scottish shores near Edinburgh.Simone Padovani/Awakening

The sediments of the seabed are considered one of the great stores of carbon dioxide (CO₂) on the planet. This greenhouse gas, which drives global warming when released and accumulates in the atmosphere, has been trapped in sea beds for thousands of years. But the fear is that certain human activities may contribute to their liberation and thereby further fuel the climate crisis. For the first time, a group of scientists has made an estimate of the amount of carbon dioxide that can be released into the ocean by trawling, a very widespread practice in the world that damages the seabed with weighted nets that are used. Their conclusion is that around 1 billion tons of CO₂ may be being pumped out of the sediments each year. “It is the same thing that the entire aviation sector emits in the world”, points out Enric Sala, the marine biologist and resident explorer of the National Geographic Society who has spearheaded this research published in part this Wednesday in the scientific journal Nature and in which 26 international experts have participated.

Sala explains that until now there was no global map of the problem or estimates of the carbon dioxide that was being released from the marine sediments with the drag weight. To make the calculations, scientists have used the satellite system that provides information on the location of trawlers in the world and have concluded that on average that gigaton of CO₂ is released annually – which would be equivalent to more than three times the emissions. of the entire Spanish economy. “It is a very conservative estimate,” says Sala.

“The sea is not only a victim of climate change, it can also be a solution,” says this researcher about the positive effects that the creation of marine protection areas would have in which trawling techniques are not allowed, which also damage biodiversity marine and contribute to the overexploitation of the fishing grounds.

It is estimated that around a quarter of the carbon dioxide generated by human activity is now retained by the oceans. The other 25% is stored by terrestrial vegetation and the remaining 50% ends up accumulating in the atmosphere and overheating the planet. “The atmosphere and the oceans are part of an integrated system,” says Sala. So if the amount of CO₂ in the water increases, this ends up having an effect on the accumulation of this gas in the atmosphere. This marine biologist maintains that a “very significant amount” of the carbon dioxide released with trawling ends up in the atmosphere, although he does not offer specific data because this scientific team is finishing finishing a specific study on this aspect.

Research published this Wednesday in Nature it goes beyond CO₂ and trawling. It delves into the benefits from the climatic, biodiversity and food point of view the implementation of marine protection areas, which currently only cover 7% of the ocean surface. This study advocates reaching at least 30% and indicates that the reduction in CO₂ emissions that would result from a reduction in trawling in these protected areas “could generate carbon credits and provide a significant opportunity to finance” the creation of these protection zones.


Sala says that this group of scientists began working on the research in 2018. In principle, the initial idea was to locate the areas that, if protected, could be beneficial for fishing. But the researchers then added benefits for biodiversity and for climate change mitigation to their estimates as well.

Regarding overfishing, this researcher points to a long conflict with the fishing industry, which has always been suspicious of the imposition of limitations on its activity and has warned of the impacts that these restrictions could have on food security. However, Sala affirms that the “worst enemy of fishing is overfishing, not protected areas”. The data suggest that, despite the fact that the marine areas with some protection figure in the world barely reach 7%, the catches continue to decrease, says this biologist. According to published research, the protection of a set of specific areas would lead to an increase in world catches by eight million tons per year – that is, an increase of 10%.

Researchers have produced several maps of the areas where there would be most benefit from their protection. And Sala points out that the vast majority are concentrated in the first 200 miles of coastline, in the so-called exclusive economic zones of the countries. In this first strip is where most of the fishing activity is concentrated because it is in which there is more abundance of fish. The authors consider the coasts of the European Union, Chile, China, Angola, the western United States and Canada as priority areas for their protection, explains Sala. “And some underwater mountain ranges in the high seas,” he adds.

“This study supports with rigorous data the benefits of protecting at least 30% of the oceans,” emphasizes this biologist in reference to the biodiversity summit that is scheduled to be held in May and had to be postponed last year due to to the covid. At this international meeting, countries are expected to set targets for land and marine protection by 2030.

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