Blueprint for a sustainable ocean

A team of scientists from across the US, Canada, Europe and Australia has devised a plan for a sustainable ocean, as reported in the journal Nature.

By taking a coordinated global approach that targets specific areas for conservation and others for fishing, the researchers say more than 80% of habitats for endangered marine species could be protected, while increasing fishing yields by more than eight million metric tonnes and reducing carbon dioxide emissions.

“For the first time we coupled the data and models for fisheries management, biodiversity conservation and climate-change mitigation to find the optimal design of marine protected areas,” says co-author Benjamin Halpern from the University of California, US.

“It is quite literally a blueprint for a sustainable future ocean.”

The study identified three main ways the oceans are of value to humans and the planet: their diverse ecosystems, food provision from seafood, and carbon storage. All three of these areas are under threat from human activities.

Yet, only 7% are currently dedicated marine-protected areas and the team says only 2.7% are properly protected in practice.

This is largely due to conflicting approaches between different sectors such as fisheries and conservation. Ocean management tends to focus on one issue at a time, without considering their interactions and impacts on each other. 

Considerably more can be achieved by taking an overarching approach writes the team, led by Enric Sala from the National Geographic Society, US: “A globally coordinated effort could be nearly twice as efficient as uncoordinated, national-level conservation planning.”

And it’s a win-win for everyone, says co-author and mathematician Hugh Possingham from Australia’s University of Queensland. “We can have our biodiversity and eat fish too, if we do smart conservation planning.”

The study shows that the world needs to protect at least 30% of its oceans to reap these benefits for humanity and the economy.

A key revelation is the destructive climate impacts of bottom trawling, a fishing method that involves dragging heavy nets across the ocean floor. Calculations showed the amount of carbon dioxide this practice releases exceeds most countries’ annual carbon dioxide emissions. Trawling releases as much CO2 annually as the global aviation sector.

“The ocean floor is the world’s largest carbon storehouse,” says co-author Trisha Atwood from Utah State University, US. “Yet every day we are trawling the seafloor, depleting its biodiversity and mobilising millennia-old carbon and thus exacerbating climate change.”

Based on available data, the authors suggest that protecting 3.6% of the oceans from bottom trawling could reduce carbon disturbance by 90%.

To build their map, the team – comprised of marine biologists, climate experts and economists – identified unprotected areas at greatest risk from human activities such as overfishing and habitat destruction. Then they created an algorithm to pinpoint regions where protection would deliver the greatest benefits across the three primary targets.

The maps provide rich detail for each coastal nation, offering priority areas that are critical for contributing to local and global needs on each level. More broadly, the study shows it’s possible to achieve more biodiversity, food provision, and carbon storage with smarter ocean management, without having to make trade-offs between different sectors.

“It’s simple: When overfishing and other damaging activities cease, marine life bounces back,” says co-author Reniel Cabral from the University of California. “With time, the ocean can heal itself and again provide services to mankind.”

The maps aren’t prescriptive but rather provide a framework for countries to choose which areas to protect depending on their national goals.

Priority areas are spread throughout the ocean, most within the 200-mile Exclusive Economic Zones of coastal nations. Others are in the high seas, which are governed by international law. These include the Mid-Atlantic Ridge, the Mascarene Plateau in the Indian Ocean, the Nazca Ridge off the west coast of South America and the Southwest Indian Ridge between Africa and Antarctica.

The study comes in time for the upcoming 15th Conference of the Parties to the United Nations Convention on Biological Diversity, planned to take place in Kunming, China this year.

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