Image courtesy of Wikimedia Commons.
By Helen Gloege ’23
Staff Writer
The ocean covers over two-thirds of the Earth’s surface and acts as a major heat and carbon sink. Despite the role it plays in mitigating climate change, it bears the brunt of our warming planet, with impacts heavily felt by marine species and ocean ecosystems. A recent study published in the scientific journal Nature found that bottom trawling emits as much carbon dioxide annually as airplanes. Bottom trawling is notorious for causing damage to ecosystems, as various forms of marine life are caught unintentionally in nets.
The trawlers also release carbon dioxide emissions into the ocean by disrupting carbon-rich sediments when raking the seafloor. Marine sediments have the largest pool of carbon storage in the world. The study found that, as of 2016, 1.47 gigatons of carbon a year were released by trawling, more than Japan’s annual emissions.
After trawling occurs, the area isn’t immediately depleted of carbon. Instead, emissions are released for up to 400 years at a rate of 40 percent of the initial year’s emissions as new layers are disrupted. This means that even if trawling were to stop, carbon dioxide would still be emitted for the next 400 years. The study recommends that countries document ocean emissions along with land-based emissions. This inventory will hold the trawling industry accountable and prevent future illegal trawling. To stop 90 percent of seabed emissions from trawling, it was estimated that only 3.6 percent of the ocean would need to be protected.
The study also mapped out areas of the ocean that, if given adequate protection, would assist in solving current climate, food and biodiversity crises. Only 2.7 percent of the ocean is strongly protected against human activity, and 7 percent of the ocean is under some form of protection. With stricter ocean protections, a greater percentage of the ocean could contribute to producing healthy seafood and provide a cheap, natural solution to address climate change. Focusing on these specific areas would safeguard over 80 percent of endangered species habitats and increase fishing catches.
The study also analyzed the world’s unprotected ocean waters based on threats by human activity. While the study doesn’t provide a single map for ocean conservation, it offers a framework for countries to address ocean protections based on their priorities. A vast majority of recommended locations are within 200 miles of Exclusive Economic Zones in coastal nations and additional areas in the high seas where the waters are governed by international law.
Ocean life has been declining worldwide due to overfishing, habitat destruction and climate change. As of 2017, about one-third of fish stocks were fished at unsustainable levels, according to the U.N. Food and Agriculture Organization. It is predicted that sustainable fish catch could drop as much as 25 percent by the end of the century. Fishing is the primary source of protein and income for many island and coastal regions. With rising temperatures, fish populations are projected to plummet and even disappear in various regions, particularly in the tropics. Fisheries are often overlooked by researchers and policymakers, as they tend to focus on land-based agriculture as a primary food source. The loss of fish as a protein source will increase pressure on other ecosystems.
A large proportion of released carbon dioxide ends up in the atmosphere while some remains in the ocean. Oceans absorb over one-third of annual carbon dioxide emissions, but this is expected to slow down, and emissions not absorbed by the ocean will end up in the atmosphere. Trawling emissions are responsible for increasing ocean acidification, lowering oxygen levels and having devastating effects on the world’s coral reefs. As a result, shellfish won’t be able to develop shells, harmful algae blooms will grow and cut off fisheries and populations of fish will move toward cooler waters, leaving behind communities and economies that have depended on them for a long time. As the ocean warms and loses oxygen, animals’ bodies will reduce in size, and the distribution of fish will change the surface production of phytoplankton that fish rely on for food.
The study added that if countries valued biodiversity and fish stocks equally, it would protect 45 percent of the ocean. This would lead to a 71 percent increase in maximum biodiversity benefits, a 92 percent increase in possible food benefits and a 29 percent increase in carbon benefits. The algorithm developed in the study aimed to identify regions where safeguarding would deliver the greatest benefits across the world. World leaders are expected to convene in Kunming, China, in May of this year at the 15th meeting of the Conference of the Parties to the U.N. Convention on Biological Diversity, which will be the most significant biodiversity negotiation in a decade. A leading group of nations is currently calling for the conservation of 30 percent of lands and 30 percent of oceans by 2030.