The nations of the world have launched a historic two-year process to create the first-ever international treaty to protect life in the high seas.

Covering nearly half of the planet, the high seas are international waters where no country has jurisdiction. These waters, which reach depths of nearly seven miles, are filled with life, from valuable fish to plankton. They help generate the oxygen we breathe and regulate the global climate.

“This is a once-in-a-generation opportunity to get ocean governance that puts conservation and sustainable use first,” says Liz Karan, senior manager for the high seas program at the Pew Charitable Trusts. “It’s said we should thank the ocean for every second breath of oxygen we take.”

The governments of Mexico and New Zealand, with over 140 government co-sponsors, coordinated the resolution. The treaty sends a "strong message of support for the high seas," according to statement by the High Seas Alliance.

After more than ten years of debate and discussion, countries voted at the United Nations on Sunday, December 24 to convene an intergovernmental conference for full treaty negotiations. Over the next two years the details of a legally binding treaty will be negotiated under the Law of the Sea Convention. This "Paris Agreement for the Ocean" would have the authority to create large marine protected areas in the high seas as ocean scientists have long called for. Among the challenges is how to protect the high seas without undermining existing organizations such as the International Whaling Commission or International Seabed Authority.

The hope is to have a treaty ready for signing by the world’s nations mid-2020. Countries are very focused on making this happen, says Karan.

Fishing’s Big Footprint

The high seas are parts of the ocean outside of the 200-mile exclusive economic zone (EEZ) of countries with coastlines. That also means the high seas are usually only fished by large vessels, often huge bottom trawlers that can damage the sea floor.

Vessels from ten rich nations, like Japan, Korea, and Spain, take 71 percent of catch from the high seas. And they’re only there because of an estimated $150 million in public subsidies that offset the costs of travelling so far from their home ports, says Rashid Sumaila, director of the Fisheries Economics Research Unit at the University of British Columbia.

Related: Learn about the benefits of marine protected areas.

The global fish catch—including the illegal catch—was recently estimated to be 109 million tonnes of fish in 2010, the most recent year available. This is roughly equivalent to slaughtering 220 million beef cows a year. And for comparison, the U.S. beef industry slaughters about 30 million cows a year.

Yet the global fish catch has been decline since the mid 1990s. A third of the worldʼs fisheries are thought to be over-exploited, up from one-tenth in the 1970s. Stocks of large fish have dwindled by an estimated 90 percent. But better protecting the high seas could help reverse these trends, Sumaila says.

Less than 10 percent of the global fish catch comes from the high seas and if subsidies were removed it would be far less—and a lot less highly-polluting bunker fuel would be burned getting there. Close the high seas to commercial fishing entirely and they’d act like a "fish bank," producing more and more fish that would boost coastal catches by 18 percent, a study led by Sumaila showed. About 70 percent of fish caught inside EEZs spend some time in the high seas.

“Restricting fisheries activities to coastal waters is economically and environmentally sensible,” he says.

The Carbon Connection

There’s also a lot more than fish in the high seas. There are countless numbers of plankton that not only feed fish and other species, but also sequester carbon dioxide (CO2). About half of all CO2 emissions from burning fossil fuels is absorbed by the ocean; the rest remains in the atmosphere heating up the planet.

In another study, Sumaila and co-author Alex Rogers of the University of Oxford estimated that marine life in the high seas soak up 1.5 billion tonnes of CO2 from the atmosphere and take it down to the seabed every year. Based on the median carbon cost from the U.S. Federal Government Interagency Working Group, this carbon removal service is worth $148 billion a year. The entire global fish catch is worth $100 billion a year.

Establishing large marine reserves in the high seas would be good for people all around the world, says Karen Sack of Ocean Unite, a network of marine conservation leaders. It would mean rich nations would get less fish from the high seas and there’d be more fish for coastal communities around the world. This protection would help the ocean be more resilient to the impacts of climate change—including acidification and warmer temperatures, which in turn will help the high seas continue to sequester CO2.

“We need a legal entity to create these reserves, and that will be this new ocean treaty,” Sack says.

The high seas also need proper governance to meet future challenges, such as mining for minerals on the sea bed, access and use of yet-undiscovered species that may have medical or commercial benefits, and geoengineering, she says. “This will be one of humanity’s most significant negotiations.”

No one thinks those negotiations will be easy. Yet most countries agree that the ocean is in trouble, and that too much lawless activity has been taking place on the high sees, from pirate fishing to human trafficking. The biggest stumbling block to change may be in the short term: how do those affected by fishing closures or other changes survive while fish stocks re-build?