Bottom trawling releases as much carbon as air transport

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For the first time, scientists have calculated the amount of carbon dioxide released into the ocean by bottom trawling practices. Answer: as much as the airline industry. Explanations.

Ocean trawling is a method of fishing which consists of dragging heavy nets on the seabed to catch seafood. If the use of this net dates back several centuries, the industrialization of this practice makes it dangerous for ecosystems . The more we scrape the seabed, the less time we allow species to reproduce. Result: the oceanic fauna becomes scarce.

But these are not the only dangers. The more we scrape the seabed, the more we damage them.

However, marine sediments constitute the largest reservoir of organic carbon of the planet. Left as is, this organic carbon can remain sequestered in the ocean floor for millennia. Conversely, disruption of these carbon stores can reactivate sedimentary carbon to CO2 – which can then increase ocean acidification, reducing their ability to absorb atmospheric carbon dioxide which ultimately accumulates more. in the air.

“The ocean floor is the largest store of carbon in the world. If we are to succeed in stopping global warming, we must leave the carbon-rich seabed intact ”, summarizes to AFP Trisha Atwood, of Utah State University, co-author of this new article published in Nature. “Yet, every day, we scrape the seabed, deplete its biodiversity and mobilize millennial carbon, thus exacerbating climate change”.

0.6 to 1.5 gigatonnes of emissions per year

As part of this work, the researchers developed a map of the carbon stored in the seabed on a global scale. They then superimposed this map with data from the NGO Global Fishing Watch, which tracks deep-sea fishing activities. Finally, they modeled the emissions released when sediments rich in carbon were disturbed by ships.

Atwood and his team then discovered that ocean trawling was responsible 0.6 to 1.5 gigatonnes of carbon emissions per year. By way of comparison, emissions from the aviation industry are estimated at nearly one gigatonne per year (around 2.8% of global CO2 emissions).

Interestingly, a very large part of this pollution occurs in less than 4% of the ocean, especially in countries’ sovereign fishing waters, known as Exclusive Economic Zones (EEZs). According to the authors, this means that these practices could be regulated much more easily than if they took place in international waters, where enforcement is difficult.

Trawling by boats in China’s EZZ area generates the largest volume of emissions (around 770 million metric tons of CO2), according to the study. Russia, Italy, UK, Denmark and France come behind.

Credit: paulbr75 / pixabay

Continuous releases

Another much less encouraging point: the researchers discovered that disturbed soils could emit CO2 for almost 400 years, has a 40% rate of initial issues (year of disturbance). For Trisha Atwood, it is “The most shocking part” of the study.

In view of these results, the researchers ask that the countries concerned begin to document these oceanic emissions in their greenhouse gas inventories. They also advocate a global agreement to protect other areas of the ocean.

To “plug” 90% of seabed emissions from trawling, only 3.6% of the ocean should be protected, according to the study. Today, only 2.7% of the ocean is fully or highly protected.

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