Negotiators from more than 100 countries completed a UN treaty to protect the high seas after 20 years of drawn-out talks.
Environmental groups say it is a long-awaited step that will help reverse marine biodiversity losses and ensure sustainable development.
The legally binding pact to ensure the sustainable use of ocean biodiversity was finally agreed after five rounds of protracted UN-led negotiations that ended in New York at the weekend, a day after the original deadline.
“The ship has reached the shore,” the UN conference president, Rena Lee said after a marathon final day of talks.
The treaty is seen as a crucial component in global efforts to bring 30pc of the world’s land and sea under protection by the end of the decade, a target known as “30 by 30” agreed in Montreal in December.
An updated framework to protect marine life in the regions outside national boundary waters, known as the high seas, had been in discussions for more than 20 years, but efforts to reach an agreement had repeatedly stalled.
Economic interests were a major sticking point throughout the latest round of negotiations, which began on February 20, with developing countries calling for a greater share of the spoils from the “blue economy”, including the transfer of technology.
An agreement to share the benefits of “marine genetic resources” used in industries such as biotechnology also remained an area of contention until the end, dragging out talks.
The European Commission, the executive arm of the European Union, hailed the agreement as a “historic moment”.
“With the agreement on the UN High Seas Treaty, we take a crucial step forward to preserve the marine life and biodiversity that are essential for us and the generations to come,” said Virginijus Sinkevicius, the European commissioner for the environment and oceans.
Greenpeace says 11 million square kilometres of ocean needs to be put under protection every year until 2030 to meet the target.
Very little of the high seas has any protection, with pollution, acidification and overfishing posing a growing threat.
“Countries must formally adopt the treaty and ratify it as quickly as possible to bring it into force, and then deliver the fully protected ocean sanctuaries our planet needs,” said Laura Meller, a Greenpeace oceans campaigner who attended the talks.
“The clock is still ticking to deliver 30 by 30. We have half a decade left, and we can’t be complacent.”
Sweden, which was involved in the negotiations as the holder of the EU’s rotating presidency, said the agreement was the “most important international environmental deal” since the 2015 Paris Agreement on tackling climate change.
The high seas have long suffered exploitation due to commercial fishing and mining, as well as pollution from chemicals and plastics.
The new agreement is about “acknowledging that the ocean is not a limitless resource, and it requires global cooperation to use the ocean sustainably,” said Malin Pinsky, a biologist at Rutgers University in New Jersey.