Is the Bigger Threat Coming From Above or Below?

We know the aviation industry releases plenty of carbon, but actions on the ocean could be just as bad when it comes to climate change.


Trawling the ocean for seafood puts enormous pressure on marine ecosystems, but a new international study further highlights why this practice stirs up trouble for the entire planet.

Many commercial fishing operations use weighted nets to gather everything from the sea floor up. Fishing this way is already widely known to shatter coral, pull out seaweed, and accidentally kill fish and other marine animals that are captured as bycatch.

Adding to this list of unintended consequences, scraping the bottom of the ocean also kicks up carbon-rich sea sediment. The study was the first to put a number on the potential release of carbon caused by bottom trawling, and it found that hundreds of millions of tons of carbon are being released into the ocean each year — a volume roughly equivalent to the entire global aviation industry.

The study includes contributions from researchers at Dalhousie University and the University of British Columbia, and was published in Nature.

“The ocean covers 70 percent of the Earth yet, until now, its importance for solving some of the most pressing challenges of our time has been overlooked,” said co-author Boris Worm in a press release.

“Smart ocean protection can help to provide natural climate solutions, make seafood more abundant and safeguard imperiled marine species — all at the same time. The benefits are clear. If we want to solve the three most pressing challenges of our century — biodiversity loss, climate change and food shortages — we must protect our ocean.”

Truly, all of these areas are interconnected, and the impact is even felt on land. The ocean is one of the most important carbon sinks on Earth, and increased carbon being released from stable sediments and into the water is amplified, because less is being withdrawn from the atmosphere.

The solution needs to address climate change and conservation at the same time. Only 7 percent of the ocean falls under marine protection; the authors suggest that strategically expanding protected areas to cover 30 percent of the ocean would not only protect important habitats and reduce carbon emissions, it would also allow dwindling numbers of fish to recover to the point where more seafood could sustainably be caught.

To assess which areas would most benefit from designation as marine protected areas — places where destructive and extractive activities would be banned — the multidisciplinary team looked through the lenses of marine biology, climate change, and economics. Their goal was to look for areas that would give the greatest benefit in terms of biodiversity, seafood production, and climate mitigation collectively.

If governments move to enact protection measures mapped out by the authors, the study estimates that 80 percent of global habitats for endangered marine species will be protected. At the same time, barring trawling in these areas is projected to reduce carbon emissions by a billion tonnes each year, while also boosting fishing catches by eight million tonnes per year.

The plan requires international cooperation, as the identified areas are scattered through zones controlled by coastal nations and in international waters. Areas that fall under Canadian control include the Fundian Channel south of Nova Scotia, the Southern Grand Banks, and the Central Coast of British Columbia.

Solutions to the pressures faced by our planet are often viewed as a zero-sum game, where trade-offs need to be made to favour either the environment and biodiversity, or food security and the economy. Changing our perspective to look at these concerns as ones that complement each other, and where changes that benefit one can raise them all, this study demonstrates that it’s possible to arrive at concrete and sustainable solutions.

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Karyn Ho is a science animator and engineer who thrives at the interface between science, engineering, medicine, and art. She earned her MScBMC (biomedical communications) and PhD (chemical engineering and biomedical engineering) at the University of Toronto. Karyn is passionate about using cutting edge discoveries to create dynamic stories as a way of supporting innovation, collaboration, education, and informed decision making. By translating knowledge into narratives, her vision is to captivate people, spark their curiosity, and motivate them to share what they learned.