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Common fishing method of bottom trawling harms both the ocean and the climate

In an alarming study released today, scientists have focused on a previously overlooked factor in climate change: bottom trawling.

This fishing practice, which involves dragging hefty nets across the ocean floor, is not just destructive to marine life and habitats, but also a significant contributor to atmospheric carbon emissions.

Bottom trawling and ocean floor carbon

The study, conducted by a global team from institutions including Utah State University, NASA’s Goddard Institute for Space Studies, and National Geographic Pristine Seas, reveals a startling fact.

55%-60% of the carbon dioxide generated by bottom trawling underwater eventually reaches the atmosphere within nine years.

This revelation is critical as the world grapples with reducing emissions from well-known sources like fossil fuels and deforestation.

“We have long known that dragging heavy fishing nets — some as large as ten 747 jets — across the ocean floor destroys sea life and habitats,” said Dr. Trisha Atwood of Utah State University and National Geographic Pristine Seas. 

“Only recently, we have discovered that bottom trawling also unleashes plumes of carbon, which otherwise would be safely stored for millennia in the ocean floor,” said Atwood.

Surprising extent of bottom trawling emissions

The scale of carbon emissions from bottom trawling is alarming. Annually, it doubles the emissions from the global fishing fleet’s fuel combustion, comprising about 4 million vessels.

Atwood explains, “Our study is the very first to show that over half the carbon released by bottom trawling eventually escapes into the atmosphere as carbon dioxide over the span of about ten years, contributing to global warming. Much like destroying forests, scraping up the seafloor causes irreparable harm to the climate, society and wildlife.”

The study titled “Atmospheric CO2 emissions and ocean acidification from bottom-trawling,” employed data and advanced models to track bottom trawling activities globally from 1996 to 2020.

The University of California Santa Barbara, Columbia University, James Cook University also contributed to this important research.

The findings are a significant leap from previous research, indicating that the carbon dioxide released into the ocean from this practice is comparable to the annual emissions of most countries and similar to those from global aviation.

Identifying high risk areas

Particularly affected regions include the East China Sea, Baltic and North Seas, and the Greenland Sea. There’s also concern about Southeast Asia, the Bay of Bengal, the Arabian Sea, parts of Europe, and the Gulf of Mexico.

However, data limitations in these areas hinder a comprehensive understanding of the full impact.

“Right now, countries don’t account for bottom trawling’s significant carbon emissions in their climate action plans,” said Dr. Enric Sala, National Explorer in Residence and Executive Director of Pristine Seas.

“Our research makes it clear that tackling these and other ocean emissions is critical to slowing the warming of the planet, in addition to restoring marine life,” Sala continued.

“The good news is that reducing bottom trawling carbon emissions will deliver immediate benefits. The bad news is, delaying action ensures that emissions from trawling will continue seeping into the atmosphere a decade from now.”

Implications and calls for immediate action

Interestingly, the study also examines the fate of the carbon that remains in ocean waters post-trawling. Findings suggest that 40%-45% of this carbon stays in the water, exacerbating local ocean acidification and harming plant and animal life.

“There are more issues with bottom trawling than just the impacts from carbon — biodiversity and sustainability for instance,” said Gavin A. Schmidt, the Director of the NASA Goddard Institute for Space Studies.

“But this ‘marine deforestation’ is large enough to be noted and assessed. Hopefully, this can lead to policy efforts that can try to maximize benefits across all of the impacts.”

In summary, this disturbing study highlights the hidden impact of bottom trawling on climate change and calls for immediate policy action to mitigate its effects.

By addressing this overlooked issue, there is potential for significant strides in both protecting our oceans and combating global warming.

More about bottom trawling

As discussed above, bottom trawling involves dragging heavy nets across the seafloor, indiscriminately capturing everything in their path and causing untold damage.

Mechanics of bottom trawling

Fishermen use bottom trawls to catch a variety of sea creatures. These large nets, weighted down with heavy gear, scrape along the ocean floor, ensnaring fish, plants, and other marine life.

The method is efficient for mass harvesting but lacks discrimination, capturing both the targeted species and a large amount of bycatch – unwanted sea life.

Environmental impact

The environmental impact of bottom trawling is profound. It destroys complex seabed habitats, home to a myriad of creatures, and disrupts ecological balance.

Coral reefs, which take centuries to form, can be decimated in a matter of minutes. This destruction leads to a loss of biodiversity, with long-term consequences for marine ecosystems and the fisheries that depend on them.

In addition, recent studies, like the one discussed previously in this article, have brought to light an alarming aspect of bottom trawling: its contribution to carbon emissions.

Disturbing the seabed releases carbon stored in ocean floor sediments, adding significantly to atmospheric CO2 levels. This aspect of bottom trawling contributes to climate change, a threat that extends far beyond the oceans.

Urgent call for change

The global community is becoming increasingly aware of the need to address the issue of bottom trawling.

Conservationists and scientists are calling for stricter regulations, protected marine areas where trawling is banned, and the adoption of more sustainable fishing practices.

The goal is to balance the needs of the fishing industry with the urgent need to protect and preserve our oceanic environments.

In summary, bottom trawling stands as a critical environmental challenge. It depletes fish stocks and destroys marine habitats while also contributing to the broader issue of climate change by emitting an enormous amount of carbon into the atmosphere.

The time for action is now, to ensure the health and sustainability of our oceans for future generations.

The full study was published in the journal Frontiers in Marine Science.


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