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Seabed trawling may be releasing millions of stored carbon emissions

Trawling the bottom of the ocean is known to destroy large spans of sea-floor ecosystems and all marine life that depend on them. Now, research shows that it may be releasing millions of tons of stored CO2 back into our atmosphere.

Using boats to drag large nets across the ocean floor in a process called ‘bottom trawling’ has long been viewed as a controversial method of fishing.

Although it is responsible for landing a quarter of all wild-caught seafood on our dinner plates – including common whitefish like cod, haddock, and hake – environmentalists often question whether destroying seafloor ecosystems in the process is worth it.

By uprooting bottom-dwelling plants and disrupting animal burrows, trawling with heavy nets demolishes large swaths of natural habitats and results in an overall decline of marine species.

Large quantities of bycatch are also a problem, as the nets are designed to trap smaller animals such as prawns, shrimp and squid, but capture pretty much everything in their path.

Recognising the destructive nature of this practice, many places including the UK and EU have placed ‘feeble’ bans on bottom trawling. These prevent fisheries from operating trawlers in Marine Protected Areas (MPAs), but allow activity to continue elsewhere.

Now, new research suggests that by tearing through the ocean floor, trawling is likely releasing as much as 370 million metric tons of carbon dioxide into the atmosphere every year.

Not exactly ideal when planetary heating is the biggest global issue of our time.

Published in the Frontiers in Marine Science journal, the new research builds on past studies which only went as far as proving that trawling was releasing CO2 into our planet’s oceans.

The 2021 study stated that continued activity would likely lead to further ocean acidification – a process which harms the ecological balance of seas and makes a normal existence difficult for a variety of plant and animal species.

Trawling causes this by stirring up carbon-storing sediment on the seabed which, without human intervention, would remain untouched for millions of years. Once disturbed, microbes begin breaking down organic material in the sediment, releasing carbon dioxide as waste that later travels around the planet via ocean currents.

In the latest batch of research, scientists claim that a large portion of this newly released carbon could be exiting the ocean and entering our atmosphere, contributing to further planetary heating.

Using computer models, they found that anywhere between 55-60 percent of the CO2 released into the ocean by trawling ends up in the atmosphere within seven to nine years. This, the researchers say, is a relatively quick timeframe.

Although 370 million metric tons of CO2 from trawling only accounts for 0.8 percent of all global emissions, every source is significant when the ultimate goal of climate summits, treaties, and other agreements is to reduce the amount of planet-warming gases in our environment.

Enric Sala, founder of the Pristine Seas project, describes it perfectly: ‘Global warming is like death by a thousand cuts,’ she says. ‘There are lots of different sources producing CO2 emissions. Everything, everything counts.’

Upon learning about the paper, some scientists have criticised the computer-based methods used. They have said that further comprehensive research is needed to ascertain whether CO2 is escaping seawater and ending up in the atmosphere.

Still, there is no denying that bottom trawling is an overall nightmare for ocean ecosystems.

It destroys some of the deepest-dwelling marine organisms, disrupts plant life that has been growing for thousands of years, and leads to the unnecessary capture of species that can’t be sold onto restaurants and supermarkets.

Considering the the ecological balance of our planet is already so skewed – we should always ask whether gambling with its future is the best move.