Can the New High Seas Treaty Help Limit Global Warming?

A framework agreement to protect open oceans is the first step toward enacting protections for ecosystems that take CO2 from the air and store it for millennia in sediments.

Fishermen pull up fish in their gillnet during a midwater pair trawl on the Gulf of Gascony sea, off the coast of France, on Jan. 8, 2020. Protecting high seas ecosystems would also benefit commercial fisheries nearer to the shore by boosting overall fish stocks. Credit: Loic Venance/AFP via Getty Images
Fishermen pull up fish in their gillnet during a midwater pair trawl on the Gulf of Gascony sea, off the coast of France, on Jan. 8, 2020. Protecting high seas ecosystems would also benefit commercial fisheries nearer to the shore by boosting overall fish stocks. Credit: Loic Venance/AFP via Getty Images

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On the high seas, outside the jurisdiction of any country’s government, lie some of the largest reservoirs of biodiversity on Earth. These vast swaths of open ocean have been called “a lawless frontier,” a place where crime and violence are beyond the reach of punishment, as reported by Ian Urbina’s Outlaw Ocean Project

Conservationists and scientists are hopeful that the new high seas treaty, agreed upon in New York on March 4, will end ecological lawlessness by protecting marine biodiversity through future policies that will also protect the planet’s climate. The agreement covers the high seas, the 50 percent of the planet that lies beyond the 200 nautical miles of jurisdiction that nations hold along their coastlines.

The treaty is seen as a critical step toward reaching global goals of protecting 30 percent of the planet’s land and oceans by 2030, and an acknowledgment that global climate goals can’t be reached without ensuring healthy ocean ecosystems. Continued degradation of the oceans and loss of biodiversity will speed up global warming. If it remains unchecked, the oceans will die.

Reaching the deal is a sign that countries are “getting the message that we really depend on the planet’s life-sustaining abilities,” said Hans-Otto Pörtner, a climate scientist at the Alfred Wegener Institute and co-chair of the Intergovernmental Panel on Climate Change Working Group II, which deals with climate impacts, adaptation and vulnerability

Civilization’s rapacious appetite for ocean resources has already disrupted the ability of coastal ecosystems like mangrove forests and seagrass beds to remove carbon dioxide from the atmosphere. That leaves more CO2 in the air, which drives more warming. The global high seas treaty offers a chance to slow down that vicious cycle by protecting parts of the ocean that have not yet been exploited. 

“This treaty doesn’t have climate as its focus,” said Lisa Levin, a marine ecologist at the Scripps Institution of Oceanography. “There are quite a few delegations that believe that climate should be left to the United Nations Framework Convention on Climate Change.”

Protecting the High Seas

Those delegations, however, did not stop Levin and others from working to recognize the critical role that marine biodiversity plays in climate mitigation. This language opens the door for the creation of marine protected areas that take the cumulative impacts of climate change and other disturbances into account. 

The treaty covers the open oceans, one of the only parts of the Earth’s surface that isn’t divided along national boundaries, similar to Antarctica, although several countries have made territorial claims there. The spirit of the treaty is that the high seas will be managed collaboratively by the whole world, for the common good, for the benefit of ecosystems and for the benefit of the climate. 

“We are not disconnected from nature,” Pörtner said. “We are dependent on it and we need to maintain the natural functioning of the planet.”

The Ocean-Climate Connection

The United Nations recognizes the oceans “as the world’s greatest ally against climate change,” central to reducing atmospheric greenhouse gas concentrations and stabilizing Earth’s climate. Oceans generate 50 percent of the oxygen in the atmosphere. They capture more than 90 percent of the excess heat trapped by greenhouse gases and absorb between 25 and 30 percent of human-caused carbon emissions.

Part of the carbon sequestration by oceans is a simple chemical reaction: CO2 molecules dissolve and react with seawater to form carbonic acid, which results in harmful ocean acidification. The second part of the ocean carbon pump is biological. In great pulses of life and decay, marine organisms capture about 33.8 million tons of CO2 daily through photosynthesis and other processes and eventually store much of it long-term in seabed sediments.

The treaty recognizes that role by calling for an integrated approach to ocean conservation that “maintains and restores ecosystem integrity, including the carbon-cycling services that underpin the ocean’s role in climate.”

Pörtner said that, in particular, marine sediments are a huge carbon store that should be left untouched and undisturbed in order to safeguard the climate. 

“We must also say that organisms in the ocean play an important role in transporting the carbon from the atmosphere down to the marine sediments,” he added. “So the treaty is an important framework agreement that will help put stocks of those organisms back to natural levels to the extent possible in order to strengthen the natural pathway of carbon export to oceans.”

Fuad Bateh, a special advisor to the State of Palestine, worked to explicitly include the link between ocean biodiversity and climate change in the high seas treaty, advocating the addition of language referencing the threat posed by ocean deoxygenation, alongside warming and ocean acidification.  

“The few wins we have,” said the Scripps institution’s Levin, “are thanks to him.”  

Levin, who studies ocean deoxygenation, said that the waning abundance of oxygen in the ocean is a direct consequence of warming. This occurs through two mechanisms. The first is that warmer water has less gas solubility and therefore can hold less oxygen. Additionally, as the ocean warms, the surface and deeper layers become more stratified. Deeper waters then have less contact with the surface ocean where they can absorb oxygen from the atmosphere. 

Areas High on the List for Future Protection

In a best case scenario for the next 10 years, the new treaty will lead to a global network of marine protected areas on the high seas, said Mary Wisz, a marine scientist at the World Maritime University in Sweden, who also trains early to mid-career diplomats and decision makers, mostly from the global south.

Management of the areas would include rigorous environmental assessments and would try to ensure an equitable distribution of resources from areas covered by the treaty, for example when it comes to genetic resources, or finding beneficial new compounds in marine species. 

“The goals of the treaty are that we’re going to protect at least 30 percent of the oceans … in the areas beyond national jurisdiction in an ecosystem-based way,” she said. “And that means that we’re going to have to balance the long term needs for healthy nature with human needs.”


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She said it’s also important that the treaty establishes environmental assessment standards “before we start any kind of exploitation. This is essential, because humans are notorious for over-exploiting unguarded regions of plenty until they become barren,” she said. “If no one’s watching the cookie jar, the cookies are gone very quickly.”

The new treaty does not directly regulate the mining of seabeds for the minerals needed for renewable energy generation and storage, or other industrial uses. Such deep sea mining is controlled by the International Seabed Authority, which is currently meeting in Jamaica through March 15 to discuss legal and technical aspects of seabed mining.

But ocean conservationists and scientists are hopeful that the treaty sends a signal that “governments can put protection, not exploitation, at the heart of our approach to the global oceans,” said Louisa Casson, who is leading the Greenpeace campaign to stop deep sea mining. 

Casson said she thinks the global tide is turning in favor of protecting oceans, and she hopes that momentum will spill over into the authority’s ongoing negotiations.

“Many governments will not want to be seen to undermine the achievement of agreeing to this treaty by giving a greenlight to deep sea mining just 2 weeks after this historic success in New York,” she said. “The standards and guidelines for strong environmental impact assessments can help raise the bar and may influence the negotiations assessing the potential for harm from deep sea mining.”

Protecting Biological Carbon Pumps in the Ocean

The High Seas Alliance, a coalition of conservation groups, has developed a list of biodiversity hotspots that they say deserve priority protection. While many of these were identified with wildlife diversity in mind, they are also critical to protecting the ocean’s biological carbon pumps.

The Sargasso Sea, in the southeastern Atlantic, and the Thermal Dome in the Eastern Pacific off the coast of Panama, are two examples of areas that could be protected under the treaty, said Rebecca Helm, a marine scientist at Georgetown University’s Institute for Environment & Sustainability who attended treaty negotiations as an observer for the High Seas Alliance.

“In the Sargasso Sea, large amounts of golden algae concentrate in these floating forests. And these forests are a really important nursery ground for diverse species of fish and also a variety of sea turtles,” she said. It’s also the only sea in the world to be bounded by four ocean currents instead of land borders, and the massive amounts of seaweed pump out large amounts of oxygen. When it dies and sinks to the seabed, it sequesters large amounts of carbon. 

A new agreement to sustainably manage the high seas would help protect marine life like these spinner dolphins off the coast of southern Mexico, and by protecting ocean ecosystems, the agreement also benefits the climate. Credit: Bob Berwyn
A new agreement to sustainably manage the high seas would help protect marine life like these spinner dolphins off the coast of southern Mexico, and by protecting ocean ecosystems, the agreement also benefits the climate. Credit: Bob Berwyn

In the Thermal Dome region, warm water from the coast meets waters from the depths in a collision that forces cold, nutrient-rich waters up to the surface, nurturing one of the world’s highest concentrations of krill, which form the base of one of the richest marine food webs known to science. 

“I’m very excited that the new treaty has language that speaks directly to those biological processes,” said Wisz, the Maritime University researcher. “It’s not just about protecting biomass in the ocean so we have fish to eat, but it’s also for protecting our climate.”

She said the treaty is also important because it considers protections for what scientists call the ocean “twilight zone” down 700 feet and deeper, where light barely penetrates. 

“It’s been estimated that in the ocean twilight zone that there could be a million undescribed species, totally new to science,” she said. “We don’t know the role that a lot of those species have in the ecosystem. We don’t know where the biodiversity is concentrated. We don’t know how it behaves, how it will interact with change that we’re bringing about in the Anthropocene.” 

What scientists do know is that the deeper waters in these biodiversity hotspots are teeming with a group of fish known as mesopelagic species, including bristlemouths, which is the most abundant vertebrate on the planet, she said.

“You can count the number of bristlemouths on this planet with a number that has 20 zeros after it. I think that’s a quadrillion,” she said. 

These fish undertake the largest daily migration of any species moving vertically to the surface to feed on carbon-rich plankton and other microorganisms by night and then swimming back down in the daytime to avoid predators. Wisz said scientists estimate that, if it were not for these vertical migrations, atmospheric carbon levels would be 50 percent higher than they are today.

“Some people joke about a zombie apocalypse or something like that,” she said. “What I really worry about is bristlemouths. I think it’s very important that we protect animals like the bristlemouth.”

How Will the Treaty Actually be Ratified?

Formal negotiations began at the U.N. in 2018 to determine language for a treaty to protect marine life in the currently lawless areas of the ocean. Ratification of the high seas treaty requires the approval of 60 countries.

Kristina Gjerde, the senior high seas advisor to the International Union for Conservation of Nature, is hopeful that the implementation of the treaty will be speedy. She and other conservationists have researched and promoted opportunities to improve high seas governance for two decades. 

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Gjerde pointed to money that the European Union, the Global Environment Facility and some foundations have said they are willing to put on the table to advance ratification and early implementation.

Additionally, she said that she expects the 54 nations who make up the High Ambition Coalition will ratify the agreement.

With language linking climate firmly to marine biodiversity, the treaty represents an ambitious new form of international cooperation, marine policy experts said.

“What I think is Earth-shaking or really critical in the agreement is the inclusion of carbon cycling,” said Gjerde. With the implementation of the agreement, fisheries management organizations “would have to look at their impacts on the biological carbon pump and make that information available.”

The treaty would introduce this regulation through the improvement of environmental impact assessments. However, there are limitations. 

Rachel Bustamante, a conservation science and policy analyst at the Earth Law Center, said that while the treaty is setting new standards for measuring and managing human activities on the high seas, “there are existing bodies responsible for regulating fishing, deep sea mining or shipping that can still continue their activities without following the treaty standards.”

The improved environmental impact assessments, as well as enforcement of future high seas regulations, could be critical to making the treaty a success, said Malin Pinsky, an ecologist and evolutionary biologist at Rutgers University.

“There will always be political pressure to enrich ourselves now, thereby impoverishing ourselves and our children later,” he said. “But if we can separate the science from the political pressures and use clear guidelines to show what impacts the ocean can sustain, then we’ll have a much better chance of succeeding and for this treaty to mean something.”