A half-planet-size gap in global governance is about to get plugged
A new treaty offers hope of curbing the destruction of the oceans
ON LAND, HUMANS’ desire to protect the richness of natural life is as old as Eden; in its modern guise, terrestrial conservation dates back to the founding in 1872 of America’s Yellowstone Park. In contrast, the desire to protect the seas’ biological diversity is more recent. More often, the ocean has been viewed as a place of plunder or pursuit: a giant global commons, a free-for-all for fishermen and the last frontier for mineral wealth. Besides in Antarctica, no global treaty has managed conservation in the high seas—less than 1% of which are formally protected.
Yet protection of the ocean beyond countries’ national jurisdictions is about to take a big leap forward, when a new high-seas treaty, with 145 signatories and ratified by 81 and counting, comes into force on January 17th. The agreement reflects a growing awareness of accelerating declines in many species of fish, sharks, turtles, squid and more. It also signals an increased understanding of the ocean’s importance in regulating the climate, since it is the planet’s biggest carbon sink. The agreement also recognises that climate change and other man-driven factors such as pollution are harming the ocean’s productivity, depleting the seas of oxygen, for instance, and harming the ability of the ocean to absorb atmospheric carbon dioxide. Still, that such an agreement has been reached in an age when multilateralism is under attack elsewhere is striking (even though America has not signed up to it). Greenpeace, a campaigning group, plausibly describes the treaty as “the biggest conservation victory ever”.
The Biodiversity Beyond National Jurisdiction agreement (BBNJ) covers all of the ocean outside countries’ individual remit, usually defined by their 200-nautical-mile (370km) exclusive economic zone (EEZ). Admittedly, many of biological hotspots, such as coral reefs, as well as most of the fish caught, are not in the high seas but within shallow and often productive EEZs. For all that, international waters account for 61% of the ocean, 43% of Earth’s surface and, with an average depth of 4,100 metres, two-thirds of its biosphere. Possibly millions of species that inhabit this space, from microbes to unknown bottom-dwelling fish, are yet to be documented.
For many scientists and policymakers the need for an agreement to protect living marine resources in the high seas is urgent. In large parts of the ocean, biodiversity—that is, the diversity of life at different scales—is in severe decline, with whole ecosystems threatened. The immense and baleful human impact on marine biodiversity is most obviously seen in a sharp decline in commercial fish stocks in the past several decades. Of 1,320 populations of 483 species in one study, 82% are being removed faster than they can repopulate.
The most prominent managers of fish stocks are a collection of 17 so-called regional fisheries management organisations (RFMOs). Yet with a few notable exceptions, such as in the western and central Pacific, the RFMOs, in essence producer lobbies, have done a poor job. For instance, the spawning population of the bluefin tuna has fallen by four-fifths in the western Atlantic in recent decades and by two-thirds in the eastern Atlantic.
Worse, they tend to be interested only in their target species and have a scanty mandate to ensure the broader health of the marine environment. Yet the size of bycatch from some of the main fishing techniques—above all, gill netting (laying vast curtains of nets) and long-lining (fishing with miles-long lines off which hang thousands of hooks)—can be staggering.
Indeed the populations of many slow-to-grow and slow-to-reproduce species, such as sharks, dolphins and turtles, which make up a significant part of the bycatch of licensed fisheries, are often devastated far more than productive target species, such as skipjack tuna, that grow and reproduce fairly quickly. A target stock is rarely fished to extinction before an unprofitable fishery is abandoned. Rather, a proportion of the population is left behind and can typically recover.
A sea of troubles
But when it comes to the population of a bycatch species, Callum Roberts of the University of Exeter points out: “You can wipe every single one of them out and no one’s paying attention.” Largely as a consequence of these fisheries’ practices, populations of oceanic megafauna have seen massive declines and at least one species, the vaquita porpoise of the eastern Pacific, is on the point of extinction. The scale of the bycatch slaughter is a key factor in helping build global support for BBNJ.
Another hugely harmful practice is bottom-trawling, where vast nets held open by heavy rollers and steel plates plough their way across the seabed. Though most such trawling takes place within EEZs, it also takes place on the high seas. This is especially damaging around seamounts. There are thousands of these underwater mountains in the Atlantic, Indian and Pacific oceans, collectively equivalent in area to all of Europe. They are often hotspots for biodiversity because they force upwellings of deep-sea, nutrient-rich currents and create crucial oases where commercial species of migratory fish feed or spawn. In 2025 a practice that was largely out of mind for the general public was brought into stark view in “Ocean”, a film by Sir David Attenborough, a British zoologist and cultural treasure. For the first time, graphic underwater shots showed a bottom-trawl in action, swallowing or flattening everything in its path and leaving desolation behind. Fragile seabed ecosystems can take centuries or even millennia to recover.
A third concern is unlicensed “dark” fleets and other illegal, unreported and unregulated fishing. Huge Chinese dark fleets in the Pacific and Indian oceans, often right next to countries’ EEZs, suck up squid, a vital prey species for many migratory fish, with harmful impacts on local fishing productivity. Such destructive activities are not always technically illegal. Indeed, most illegal activity takes place on licensed vessels—skippers who take more fish than they have a permit for, or who use illegal nets with too fine a mesh or who cut the fins off sharks for sale to China.
This is the context in which the BBNJ agreement has emerged. It has three broad legs. The first concerns marine genetic resources, a field that may prove valuable in future, not only for the scientific documenting of the ocean’s carnival of life, but also for developing commercial products such as pharmaceuticals. Since the high seas and all that is in them formally belong to all humanity, smaller, poorer signatories are concerned to get an equitable share of any benefits, including through the transfer of knowledge and technology. For the first time, the BBNJ offers a framework. (President Joe Biden’s administration was key in helping draw it up.)
A second leg is the obligation to carry out robust environmental assessments for any planned activity that might have an impact on the workings of the ocean. A “clearing-house mechanism” is also envisaged for sharing the findings of such assessments as well as for promoting technology transfer.
The most important leg is a template for protection. The high-seas treaty creates a process for establishing a network of marine protected areas (MPAs) around the world. It is crucial that these should be both large and interconnected, given the distances that many species, from megafauna like whales to tiny organisms drifting on the current, travel for food or to breed. Scale and connectivity also help boost resilience in ecosystems under stress from a warming climate.
The new high-seas treaty does not specify a target for future protection. However, UN members have pledged, under another agreement, the Convention on Biological Diversity, to protect 30% of their land and waters by 2030. The aim, says Lisa Speer, who has been heavily involved in the BBNJ process at an American environmental advocacy group, the Natural Resources Defence Council, is to extend that target to the ocean. Many wish for even more protection than that. One concern is the fishing industry’s interest in going after mesopelagic fish, the most abundant vertebrates on Earth, which inhabit a mysterious “twilight zone” in the depths below 200 metres. The life in that zone, recent research shows, is a crucial regulator of the ocean’s ability to absorb carbon dioxide.
A tide in the affairs of men
What and where to start to protect? One obvious answer is those areas with the greatest biological productivity. As long as two centuries ago, whaling captains knew exactly where many of those areas were, as did the whales they were targeting. Large whales are no longer hunted. But another striking shot in Sir David’s “Ocean” was taken near the Antarctic Peninsula, a crucial feeding ground for whales and near the breeding grounds of seals and penguins. It showed giant factory ships moving close among numbers of whales as they hoovered up vast quantities of krill, tiny crustaceans that are a building-block of ocean life (and are caught for fish meal and health supplements). Carry on like that and there won’t be much wildlife left there. It would be far better for krill to be taken in less productive areas, even if that would require more fishing effort. Discreet discussions are under way with Norway and other fishing states about enhancing protection in this part of the Southern Ocean.
Peter Thomson, the UN secretary-general’s special envoy for the ocean, counts a dozen “cabs off the rank”: MPAs being drawn up by UN members and marine experts ready to be put in place. They include the Salas y Gomez and Nazca Ridge east of Easter Island; the Lord Howe Rise, an underwater plateau extending south-west from New Caledonia; and the Emperor Seamount Chain north-west of Hawaii. In the Atlantic, west African countries are interested in protecting the Canary and Guinea Currents. (One incentive for neighbouring states is the “spillover” effect of more fish entering their EEZs.)
But first, a bureaucracy and funding rules need to be put in place. A “conference of parties” later in 2026 is necessary to enable the treaty’s full operation. Both formal and informal talks are taking place between now and then to bring about agreement on the treaty’s workings. Any number of frustrations could trip or slow the process. Yet the tide seems to have turned, and the best chance in years for protecting the high seas is there for the taking. ■