The Entire High Seas Could Become One Giant Multi-Use Marine Protected Area

Half the surface of planet Earth belongs to no single nation. These Areas Beyond National Jurisdiction—ABNJ in the shorthand of ocean law—include the open water column of the high seas and the seabed beneath it, with its mineral riches, known under the United Nations Convention on the Law of the Sea as “the Area.” Now, a new perspective published in Frontiers in Ocean Sustainability argues that the world’s freshly minted High Seas Treaty should be read in a radically ambitious way: as a mandate to manage the entirety of ABNJ as a single, de facto multi-use marine protected area, with conservation and sustainable use as the default priority for every decision made there.

The argument arrives at a pivotal moment. The BBNJ Agreement—the treaty on biological diversity beyond national jurisdiction, adopted in June 2023 after two decades of negotiation—entered into force on 17 January 2026. It reached its ratification threshold of 60 signatories in just 27 months, dramatically faster than the roughly 90-month average of the previous five ocean-focused multilateral environmental agreements developed since 1970. That speed, the author suggests, may reflect genuine willingness to protect the global ocean commons—or, more cynically, political confidence that the treaty will leave national self-interest largely untouched.

The treaty’s operational power is deliberately constrained. It commits parties to “respect the competence of” and “not undermine” existing instruments, frameworks, and bodies: the International Seabed Authority for seabed minerals, the International Maritime Organization for shipping, and Regional Fisheries Management Organizations for fisheries. In practice, this deference means the BBNJ Agreement’s flagship tools—environmental impact assessments, area-based management tools including marine protected areas, sharing of marine genetic resources, and capacity building—can only be deployed in coordination with institutions that have, in some cases, struggled to deliver sustainability on their own. The proportion of marine fisheries regulated outside UNCLOS with unsustainable catch levels continues to rise, and the ISA’s provisions for large-scale deep-sea mining are widely judged inadequate for the prospect now looming.

Geopolitics sharpens the problem. The United States has signed the BBNJ Agreement but never ratified UNCLOS, and is pushing ahead with unilateral seabed mining plans as a non-member of the ISA. Even states that are parties to UNCLOS are increasingly attempting to extend exploitative control over ABNJ by claiming extended continental shelf areas and contesting interpretations of the convention’s principles. The treaty’s third preparatory commission session, which concluded in April 2026, left unresolved institutional boundary questions that will now have to be settled at the first Conference of the Parties, scheduled for January 2027.

Yet the deeper challenge, the analysis argues, comes from outside the treaty itself: from global environmental change and from activities on land and in national waters that reach into ABNJ whether anyone manages them or not. Rivers deliver land-generated pollution through coastal waters into the high seas. Catching migratory fish such as tuna in national waters alters population ecology across ABNJ. Rising extraction of fisheries biomass threatens the marine diversity that constitutes the biological carbon pump—the transfer of organic carbon from the upper ocean to the deep ocean that helps regulate the planet’s climate.

The stakes are planetary in scale. The high seas water column accounts for 90 percent of the volume of an ocean that has absorbed 30 percent of anthropogenic carbon dioxide emissions to date and more than 90 percent of the additional heat energy in the climate system. Climate change is already reshaping ABNJ through ocean acidification, warming, increasingly frequent marine heatwaves and El Niño events, growing stratification, and shifting current patterns and species distributions. Ironically, the very effort to decarbonize threatens these ecosystems: demand for rare earth elements for clean technologies drives interest in seabed mining, and proposed ocean-based climate interventions, from large-scale marine carbon dioxide removal to ocean thermal energy conversion, would carry deep-ocean impacts and substantial risks for a rapidly changing ocean.

Some scientists have argued for the boldest possible response: protecting the whole of the high seas and seabed from all extraction, forever, because of its importance for biosphere resilience and climate stability. Stopping industrial fishing in ABNJ might be viable—high seas fisheries contribute only about 4.2 percent of global wild capture totals, and main targets such as migratory tuna are largely caught in national waters anyway. Seabed mining could perhaps be minimized, since deep-sea deposits exist within national jurisdictions. But the perspective argues that complete zero-extraction is geopolitically unlikely given state self-interest, and potentially counterproductive: economic activity incentivizes the commercial funding of research and management that could help close the vast knowledge gaps about ABNJ. It would also be inequitable, since all states hold equitable rights to ABNJ under UNCLOS—the only marine resource rights available to landlocked countries.

The proposed middle ground is a creative reading of the treaty’s own text. Article 1(9) defines a marine protected area as a geographically defined marine area designated and managed to achieve specific long-term biodiversity conservation objectives, which may allow, where appropriate, sustainable use provided it is consistent with those objectives. Article 2 states the agreement’s objective is to ensure the conservation and sustainable use of marine biological diversity of areas beyond national jurisdiction for the present and in the long term. Read together, the author contends, these provisions already describe ABNJ in their entirety as a multi-use MPA. Under this framing, extraction would be accepted only if it does not diminish conservation outcomes—and could even be desirable if it carries associated infrastructure or research that supports conservation.

Practically, the framework would run through the treaty’s existing environmental impact assessment provisions. Article 28(2) requires an EIA when a planned activity in ABNJ may cause substantial pollution of, or significant and harmful changes to, the marine environment—a threshold that effectively applies to any proposed activity once the treaty’s explicit adoption of the precautionary principle is factored in. But the EIA process is devolved to national systems with widely recognized failings, so the Scientific and Technical Body would need to develop standards and guidelines under Article 38 that embed an ecocentric framing prioritizing conservation objectives. Decisions devolved to existing bodies such as the ISA would need to apply the same “sustainable use consistent with conservation objectives” principle as part of an ongoing, flexible, iterative development of the treaty’s delivery mechanisms.

Taking the idea forward, the perspective argues, requires institutional advocacy through the BBNJ Conference of the Parties, complemented by political platforms such as the High Level Panel for a Sustainable Ocean Economy, and broad agreement across the existing governance bodies whose cooperation the “not undermine” clause demands. Implementation—determining conservation objectives, assessing activities and infrastructure, monitoring and enforcement—could be led by the COP or Secretariat in coordination with existing bodies. Crucially, the author argues the BBNJ Agreement should establish itself as a focal point not just for ABNJ, but for integrating ocean sustainability with the broader triple planetary crisis of climate change, biodiversity loss, and pollution, as part of the upcoming post-2030 sustainable development agenda. If the argument gains traction, the largest protected area on Earth may turn out to be one that already exists in law—waiting only to be recognized.

Subject of Research: Ocean governance and the BBNJ Agreement

Article Title: The high seas treaty (BBNJ agreement) and planetary sustainability: why we should manage the entirety of ABNJ as a de facto multi-use marine protected area

Article References: Moolna, A. (2026). The high seas treaty (BBNJ agreement) and planetary sustainability: why we should manage the entirety of ABNJ as a de facto multi-use marine protected area. Frontiers in Ocean Sustainability, 4, Article 1857777. https://doi.org/10.3389/focsu.2026.1857777

Image Credits: AI Generated

DOI: 10.3389/focsu.2026.1857777

Keywords: BBNJ Agreement, High Seas Treaty, ABNJ, marine protected areas, ocean governance, deep-sea mining, biodiversity conservation, UNCLOS, triple planetary crisis, sustainable use, high, seas