Landsat image of the waters off the coast of Pecan Island, Louisiana, showing numerous sediment plumes, taken in 1999. Image by SkyTruth / Flickr. (CC BY-NC-SA 2.0).

World - Ocean protection scheme can yield 'triple benefits' study says

A new study suggests that carefully planned marine protected areas could yield triple benefits for the ocean, helping to maintain biodiversity, while also increasing fish yields and maximizing the ocean’s ability to sequester carbon in seafloor sediment.

  • This study is one of the first to quantify the carbon footprint of ocean trawling, which it equates to the yearly emissions of the global aviation industry.
  • The researchers suggest that the planning tools in this study could help inform discussions about how to protect 30% of the oceans by 2030, a goal that is expected to be adopted by the U.N. Convention on Biological Diversity later this year.
  • Other proposals for how to achieve 30% protection by 2030 have mostly focused on the high seas, but this plan takes all parts of the ocean into consideration.

From the eye of a satellite, the ocean is streaked with smoky white lines that flow and twist like scribbled handwriting across the surface. But these lines aren’t naturally occurring features — they’re sediment plumes from large trawling vessels that scrape the seafloor with nets and heavy equipment, trying to catch bottom-dwelling species like shrimp and whiting.

The environmental consequences of trawling are still being investigated since the plumes were first noticed in satellite imagery in 2008. But a new study in Naturesuggests that it churns up and releases carbon that’s been locked up inside sediment at the bottom of the ocean — between about 600 million and 1,500 million tons, according to the study’s initial estimates, which is about the same amount as the global aviation industry.

“It had been thought before that there’s more carbon stored in soils than there is in sediment in the ocean,” Boris Worm, co-author of the paper and professor of marine conservation biology at Dalhousie University in Canada, told Mongabay in an interview. “But we found that the ocean was qualitatively more important. So then it becomes an important question of whether that carbon is safe, or whether there is a danger that it gets reintroduced into the environment.”

The paper, which was spearheaded by Enric Sala of National Geographic and the Pristine Seas project, not only points out the issue of trawling emitting carbon — it also offers a solution, or rather, a range of solutions. It suggests that by meticulously choosing places in the global ocean to set up as marine protected areas (MPAs), nations can not only reduce carbon emissions, but also safeguard marine biodiversity and maintain fishing efforts.

“The basic idea is to try to optimize on multiple objectives at the same time so you’re essentially killing two fish with one stone, so to speak, or in this case three fish,” Worm said. “This was a primary question we had — are there areas in the ocean that can fulfill these multiple objectives, and if so, can we find them, and can we point out to the international community where they are [to not] just protect species, but at the same time produce more food and at the same time preserve the climate?”

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