Humanity has no better friend on this planet than the ocean. It provides more than half the oxygen we need to breathe. It supplies food that helps sustain more than 3 billion people. It absorbs many of the pollutants we keep pumping into the atmosphere: carbon dioxide, ozone-depleting chemicals.
The ocean is the kind of unwaveringly supportive friend who tolerates our toxicity and shields us from the worst consequences of our actions. It’s the friend that people have taken for granted for far too long. By overfishing and mining and drilling the sea floor, humanity is risking not just the ocean’s health but our own.
But new research suggests a strategic, globally coordinated effort to protect more of the world’s waters could not only bolster marine biodiversity but dramatically increase the number of fish available for harvest and boost the amount of carbon taken up by the ocean, aiding the fight against climate change.
The research, published Wednesday, March 17, in the journal Nature, comes weeks before a United Nations biodiversity conference at which nations will set new targets for conserving plants, animals and the ecosystems they inhabit. Many countries, including the United States, have said they aim to protect 30 percent of their lands and waters by 2030.
“Now there are scientific and economic studies showing that not valuing nature is a great existential risk to humanity,” said conservationist Enric Sala, an explorer-in-residence at National Geographic and a lead author of the report. “But if we protect the right places … it’s a ‘win-win-win’ situation.”
According to the United Nations, just 7.65 percent of the ocean is currently in a marine protected area, a designation that indicates some level of oversight of human activities. Yet many of those supposed protections are insufficient, Sala said: They still permit some commercial fishing or are weakly enforced. The portion of the ocean that is “strongly” protected is under 3 percent.
The new 30 percent goal embraced by the United States and other nations is the minimum amount of protection required, Sala said. If the world established 45 percent of the ocean as a marine protected area, the result would be much healthier fisheries, richer biodiversity and enhanced carbon uptake, he said.
The finding is the result of three years of work by more than two dozen ocean experts. The researchers carved the ocean up into 50 kilometer by 50 kilometer squares, then evaluated each plot for the threats it faced, the number of species it contained and the uniqueness of those creatures, as well as the abundance of any of the 1,300 most economically important fish.
They also built the first global map of carbon stored in the sea floor, discovering that marine sediments store twice as much carbon as terrestrial soil.
Finally, the team developed a model that could calculate a conservation strategy that optimized for all three benefits — biodiversity, fisheries and carbon sequestration — where establishing a robust marine protected area could deliver a “triple win.”
The resulting maps indicate that many of the best areas to protect are within 200 miles of coastlines, in the “exclusive economic zones” where nations have jurisdiction over natural resources. They include parts of the China Sea and the Adriatic and encompass species-rich coral reefs, unique kelp forests and carbon-rich wetlands.
Other “triple win” areas are centered on mid-oceanic ridges, where the seafloor is ripped open by plate tectonics, and seamounts — where underwater volcanism gives rise to submarine peaks. The nutrient-rich waters around Antarctica are another target area for protection.
The analysis also highlights the climate risks associated with bottom trawling, a fishing practice that involves dragging a net across the sea floor.
“It’s such a destructive method of fishing,” said Trisha Atwood, a Utah State University ecologist who performed much of the carbon analysis for the report.
Much the way plowing a field unleashes carbon stored in the soil, trawling tosses buried carbon back into the water column, where it may be eaten by bacteria and turned into carbon dioxide. The study suggests that the carbon emissions generated by bottom trawling are equivalent to that of the global airline industry.
Atwood and her colleagues are still analyzing how much of that carbon dioxide makes it into Earth’s atmosphere. But it can worsen climate change even if it remains in the water by hindering the ocean’s ability to absorb other emissions linked to human activities.
“The ocean is our greatest carbon sink right now,” Atwood said. “The more carbon dioxide we add to it the less it is able to take up.”
People can curb the risk of carbon disturbance from bottom trawling by 90 percent simply by protecting 3.6 percent of the ocean, the analysis found. This would help the world meet the goal of almost halving emissions by 2030 to keep warming “well under” 2 degrees over preindustrial levels — the United Nations-designated threshold for “catastrophic warming.”
Allowing countries to count these carbon savings toward their commitments under the Paris Climate Agreement would offer an incentive for them to pursue protections, Atwood said. China alone could prevent the release of 769 million metric tons of carbon dioxide each year by stopping bottom trawling — delivering a climate benefit equal to pausing 198 coal fired power plants for a year.
Activists are hopeful that the report will bolster the case for ocean conservation when world leaders meet for the U.N. conference in Kunming, China, this May. Sala said the meeting is comparable to the Paris agreement, but for conservation.
“There’s this false narrative of conservation versus the economy,” said Marce Gutiérrez-Graudiņš, founder and executive director of the grassroots Latinx ocean conservation group Azul. She can empathize with fishing industry workers worried about their livelihoods — Gutiérrez-Graudiņš worked for a commercial seafood company before becoming an activist.
“But this shows you can have a win-win,” she said. “And if you’re actually doing this as a long-term enterprise it’s in your best interest that this resource stays out there.”