Environmental advocacy groups heralded the finalized text — which still needs to be ratified by the United Nations — as a new chapter for Earth’s high seas. Just 1.2 percent of them are currently environmentally protected, exposing the vast array of marine species that teem beneath the surface — from tiny plankton to giant whales — to threats such as pollution, overfishing, shipping and deep-sea mining.

“Two-thirds of the ocean has just been exposed to the will and want of all,” said Rebecca Hubbard, the director of the High Seas Alliance consortium of nongovernmental organizations that participated in the negotiations, in a telephone interview Sunday. “We have never been able to protect and manage marine life in the ocean beyond countries’ jurisdictions,” she said. “This is absolutely world-changing.”

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Despite U.N. members agreeing to a final version of the text, it is expected to take years for the treaty to be formally adopted by member states and come into force. The United States, in particular, is often slow to ratify environmental treaties — and often will decline to approve them at all.

Once the treaty takes legal effect, nations can begin proposing the establishment of new marine protection areas. Even then, enforcement will remain a challenge. International waters today are a Wild West of sorts, with little to no policing. Illegal fishing runs rampant and some seafood vessels even use slave labor.

Still, the treaty is a much-needed start to conservation on the high seas as the pressures on the world’s oceans increase.

Climate change is making the oceans less hospitable for many species by driving up aquatic temperatures and making the seas more acidic. Global trade means more ships that can strike whales and other animals near the surface. Much deeper underwater, the need for minerals that drive international commerce has companies preparing to mine the seafloor. At the same time, the degradation of the oceans’ ecosystems reduces their ability to absorb carbon and help keep climate change in check.

The treaty also advances a way to tackle a pressing issue: how to divvy up the profits from deep-sea scientific discoveries.

“This action is a victory for multilateralism and for global efforts to counter the destructive trends facing ocean health, now and for generations to come,” Stéphane Dujarric, spokesman for the U.N. secretary general, said in a statement after the agreement. “It is crucial for addressing the triple planetary crisis of climate change, biodiversity loss and pollution.”

How will the ocean treaty work?

A country’s legal authority generally extends 200 nautical miles from its shores. After that are the high seas, where no one nation is in charge.

The new agreement will not automatically establish any new marine protection areas in the high seas, but it creates a mechanism for nations to begin designating them in international waters for the first time. That ability is crucial for enforcing the promises made at last year’s U.N. biodiversity summit, COP15, where delegates pledged to protect nearly a third of Earth’s land and oceans by 2030 as a refuge for the planet’s remaining wild plants and animals.

The high seas treaty makes it easier for that goal to be reached, as it allows vast swaths of vulnerable marine ecosystems in international waters to be subject to protections. It will also offer protections for millions of organisms inhabiting the high seas — Earth’s largest physical habitat, Hubbard said.

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In the oceans, many sea stars, sturgeon and other species are already on the decline. Sharks are threatened by overfishing, and coral reefs are succumbing to the acidification of the oceans. The deterioration of marine ecosystems could hurt billions of coastal residents who depend on seafood for protein.

Among the biodiversity hot spots to which marine conservationists want to extend protections are the Sargasso Sea in the Atlantic and the Costa Rica Thermal Dome in the Pacific.

Splitting up the bounty of the seas benefits

The new agreement is the first of its kind to protect oceans since 1982, when the U.N. Convention on the Law of the Sea was adopted, establishing a single set of rules that governed the world’s oceans and their resources.

The treaty’s final text had not yet been published in full as of Sunday, but according to the State Department, it also establishes frameworks for nations to coordinate on environmental impact assessments and to share marine genetic resources — scientific knowledge about deep-sea organisms found in remote waters that could be of value to humankind.

One of the biggest sticking points in negotiations between rich and poor nations was determining who would benefit financially from discoveries made on the high seas.

Who profits, for example, when scientists find a compound in a sea creature that treats a disease in humans? In 2010, for instance, the Food and Drug Administration approved the use of a cancer-fighting drug derived from a sea sponge.

Nations promise to protect 30 percent of planet to stem extinction

“Developing countries typically don’t have the technology, the access and the resources to do research in the high seas,” said Liz Karan, director of ocean governance at the Pew Charitable Trusts.

Ultimately, developed nations agreed to share some of those profits with developing ones, Karan said.

What about climate change?

Though the treaty’s main goal is safeguarding life in Earth’s seas, it will also help efforts to fight climate change. Research published in the journal Nature in 2021 suggested that efforts to protect more of the world’s waters would not only support marine diversity, but would also boost the amount of carbon absorbed by the ocean.

How protecting the ocean can save species and fight climate change

“The ocean is also — physically — our biggest ally in the fight against climate change,” said Hubbard of the High Seas Alliance. “Without an ocean full of marine life, it cannot continue to sequester and store carbon.”

“We have a degraded ocean on our hands, but the ocean has a phenomenal capacity to restore itself.”

Sarah Kaplan contributed to this report.