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

1 Introduction

The “High Seas Treaty” that came into force on 17 January 2026—the BBNJ (Biological diversity of areas Beyond National Jurisdiction) Agreement (United Nations, 2023)—is an agreement under the United Nations (UN) Convention on the Law of the Sea (UNCLOS). Economic activities, both existing sectors and new types of exploitation, are expanding in scale and space across the ocean and increasingly into the global commons of Areas Beyond National Jurisdiction (ABNJ) that account for half the surface of our planet (Jouffray et al., 2020). Importantly, ABNJ include both the water column of the High Seas and the seabed with its mineral resources (known as “the Area” under UNCLOS). UNCLOS has a general obligation to safeguard the marine environment but, before the BBNJ Agreement, had limited provision for conservation and sustainable use of marine resources in ABNJ—other than seabed mineral resources through the International Seabed Authority (ISA).

The BBNJ Agreement aims to address governance gaps for environmental protection of ABNJ reconciled with development interests (Bodansky, 2024). It provides a framework for Environmental Impact Assessment (EIA), for Area-Based Management Tools (ABMTs) including Marine Protected Areas (MPAs), for sharing of Marine Genetic Resources, and for Capacity Building and Transfer of Marine Technology in ABNJ (Blasiak and Claudet, 2024).

Effective action under the BBNJ Agreement, however, faces challenges for participation and compliance. The operational scope, for example, is limited by the commitment to “respect the competence of” and “not undermine” existing instruments, frameworks, and bodies (IFBs; United Nations, 2023), such as the ISA for seabed mineral resources, the International Maritime Organization (IMO) for shipping, and Regional Fisheries Management Organizations (RFMOs). This is concerning because, for example, the ISA has substantially inadequate provisions for the emerging prospects of large-scale deep-sea mining (Amon et al., 2022) and the proportion of marine fisheries (regulated outside of UNCLOS by RFMOs; Carmine et al., 2025) with unsustainable catch levels continues to increase (FAO, 2024). Interpretation of obligations is complicated by states that have signed the BBNJ Agreement but not UNCLOS and may resist implied obligations to UNCLOS principles—such as the United States of America (USA).

A substantial, and perhaps greater, dimension of challenge is added by the continuing general decline in ocean health (Sumaila et al., 2021) and “indirect” impacts due to global environmental change and activities in national waters and on land. Meaningful delivery of the BBNJ Agreement therefore needs integrated multi-sectoral, multi-issue, and hybrid regional to global action across ABNJ, national waters, and terrestrial environments. This requires framing the BBNJ Agreement as part of global sustainable development and action addressing the broader triple planetary crisis of climate change, biodiversity loss, and pollution—and pressures from land-based activities and climate change integrated into ABNJ governance approaches. It has been suggested that we should consider protecting the whole of the High Seas (and seabed, i.e., ABNJ) from all extraction because of its importance for biosphere resilience and climate stability (Roberts et al., 2025). The political and economic attraction of exploitation options, however, make this geopolitically unlikely. It may also be counter-productive for scientific and sustainability progress because ABNJ require better scientific understanding and human input to help their protection (Jarvis and Young, 2023), which is closely linked to the resources and interest that some level of economic use empowers. Instead, we might more realistically focus on how ABNJ could be managed in their entirety as a de facto multi-use MPA—with sustainable use in appropriate areas allowed only when it is consistent with overall long-term biological diversity conservation objectives (using the MPA definition in the BBNJ Agreement; United Nations, 2023).

This Perspective aims to evaluate implementation challenges for the BBNJ Agreement within a planetary sustainability framing and to present an argument that ABNJ should be managed as if they were a multi-use MPA in their entirety. The priority in all decision-making would be conservation and sustainable use because of the overwhelming importance of ABNJ for biosphere resilience and climate stability. The first section outlines key challenges including limitations to operational scope, the dependence on soft power influence, and the importance of the broader ocean context and global environmental change. The second section evaluates how ABNJ as a de facto multi-use MPA within planetary sustainable development would support meaningful delivery of the BBNJ Agreement, with discussion of how this might be taken forward.

2 Challenges to meaningful delivery of the BBNJ agreement

The BBNJ Agreement (formally adopted on 19 June 2023 after 2 decades of negotiation) met the ratification threshold of 60 signatories after just 27 months, much faster than the 90 months (2,688 days) that was the average for the previous 5 ocean-focused multi-lateral environmental agreements developed since 1970 (Blasiak and Jouffray, 2024). This might reflect states' willingness to engage in protection of ABNJ. Concerningly, however, it might also reflect that politicians are reassured the BBNJ Agreement will have limited impact on national self-interest and ability to act. States' different obligations (and interpretations of these) to the BBNJ Agreement, UNCLOS, and other IFBs threaten to undermine compliance and participation. The USA, for example, is a signatory to the BBNJ Agreement but not UNCLOS—and is pushing ahead with plans for unilateral seabed mining in ABNJ as a non-member of the ISA (Lathrop, 2026; Willaert, 2021; Willaert and Soete, 2025). Even states that are signatories to UNCLOS are increasingly trying to extend their exploitative control of ABNJ by claiming further areas of continental shelf or enhanced rights and have contested interpretations of UNCLOS principles (Lambach, 2021).

The immediate issue for BBNJ Agreement implementation therefore seems to be how it can work synergistically with existing polycentric ocean governance (Lin and Tsai, 2026). The biggest inherent risks for effectiveness come from ambiguities in power and scope, with the explicit obligation to “respect the competence of” and “not undermine” existing IFBs (Kim and Kim, 2025). Actual uptake of measures offered by the BBNJ Agreement (such as EIA and MPAs) is constrained by deference, for example, to RFMOs for fisheries and to the ISA for seabed mining.

The BBNJ Agreement instead aims to influence existing IFBs through “soft power” to consider ABNJ in their approaches—establishing a normative weight on the obligation to prevent irreversible harm to marine biodiversity and an expectation for ecosystem-based management and spatial planning (Kim, 2024). Growing public and political awareness of the ocean's importance to humanity (“ocean literacy;” McKinley et al., 2023) has driven forward societal engagement with ocean sustainability, providing generalized soft power support for ocean sustainability measures. Examples include the declaration of 2021–2030 as the UN Decade of Ocean Science for Sustainable Development, the emergence of political platforms such as the High Level Panel for a Sustainable Ocean Economy (“The Ocean Panel” of 19 world leaders), and concerns over marine plastic (Tiller et al., 2019).

Despite the requirement for Parties to the Agreement to promote BBNJ objectives within other bodies (Kim, 2024), there are concerns about whether the BBNJ Agreement will be able to exert much influence on, for example, RFMOs when they are failing to deliver sustainable fisheries governance in even national waters (Sebuliba et al., 2025). Ambiguity and under-articulated provisions for ABMTs including MPAs may limit effective implementation (De Lucia, 2024), as does dependence on the ISA for seabed mining governance when it has limited enforcement provisions (Currie and Müller, 2025). The integration of conservation and sustainable use in ocean sustainability is underdeveloped and contested (Kittinger et al., 2024) and tensions between the concepts remain across the BBNJ Agreement.

Importantly, however, these issues and the practical implications of the “not undermine” clause will evolve and be shaped by a developing polycentric network of relations between the BBNJ Agreement (including the Conference of Parties (COP), Secretariat, and subsidiary bodies) and existing IFBs. Arrangements to enhance cooperation with relevant IFBs and global, regional, subregional and sectoral bodies have advanced in negotiations through the Preparatory Commission for the BBNJ Agreement (BBNJ PrepCom; established by UN General Assembly resolution 78/272). The final of 3 sessions (PrepCom III) concluded in April 2026, however, with issues remaining that need resolving at COP1—particularly around institutional boundaries (Tsioumani and Calabretta, 2026). Establishing the inter-institutional alignment of the BBNJ Agreement COP with relevant IFBs is likely to dominate the first few COP meetings (Kim and Kim, 2025).

Crucially, there is a wider issue for BBNJ Agreement implementation posed by sustainability challenges both across regional seas and on a global scale. The ocean and ABNJ also offer a critical arena for action on the triple planetary crisis (climate change, biodiversity loss, pollution). Coordination is therefore needed with climate action and sustainable development, as well as broader ocean governance. Connecting advocacy for conservation and sustainable use in ABNJ to wider action addressing the climate crisis and sustainable development does, however, offer substantial opportunity to enhance the soft power needed for effective delivery of the BBNJ Agreement.

ABNJ are, for example, functionally connected with coastal and national waters by ocean currents and as part of regional marine ecosystems that overlap national and international jurisdictions. Human activities taking place on land and in national waters impact ABNJ and must therefore be included in ABNJ management considerations. Activities on land generate pollution that is delivered by rivers into coastal waters, regional seas, and then ABNJ (O'Leary et al., 2020). In national waters, catching migratory fish such as tuna alters population ecology and affects associated parts of ecosystems across ABNJ (Fortuna et al., 2024). Increasing fisheries biomass extraction, mainly in national waters but with impacts across ABNJ, is putting at risk the marine diversity that constitutes a biological carbon pump transferring organic carbon from the upper to the deep ocean (Henson et al., 2022; Roberts et al., 2025)).

Designation of MPAs under the BBNJ Agreement is argued to be of key importance in meeting the Kunming-Montreal Global Biodiversity Framework's “30 by 30” aim to protect 30% of the ocean and land by 2030 (Blasiak and Jouffray, 2024). But MPAs in ABNJ need to be part of coherent regional and global networks with MPAs in national waters that encompass complex patterns of biodiversity, ecological interactions, ocean productivity, and human impact (Moolna, 2026) to efficiently deliver biodiversity protection, boost fisheries, and secure marine carbon stocks (Sala et al., 2021). Ocean sustainability is facing growing crises of declining ocean health (Sumaila et al., 2021) and social justice concerns (Bennett, 2022) despite extensive political and scientific efforts to manage human impacts on the ocean in line with the principles of an equitable and sustainable Blue Economy (“socially equitable, environmentally sustainable and economically viable”; Cisneros-Montemayor et a1., 2021).

On a global scale, climate change (driven primarily by activities on land such as fossil fuel burning) has critical impacts on ABNJ including ocean acidification (Duarte et al., 2013), ocean warming (with increasing frequency of ocean heatwaves and El Niño–Southern Oscillation events; Hobday et al., 2023), ocean stratification (Cheng et al., 2025), and changes in ocean current patterns and marine species distributions (García Molinos et al., 2017). The High Seas water column of ABNJ accounts for 90% of the volume of an ocean that has absorbed 30% of anthropogenic carbon dioxide emissions to date (Gruber et al., 2019) and over 90% of the additional heat energy in our climate system (Pan et al., 2026). Climatic regulation mechanisms within ABNJ are at risk of disruption, including global heat redistribution because of changing ocean currents (Mecking and Drijfhout, 2023) and the biological carbon pump because of ocean acidification (Barrett et al., 2025).

Ironically, societal efforts to mitigate climate change by decarbonizing further threaten the integrity of ecosystems in ABNJ. Interest in seabed mining is driven by demand for rare earth elements used in clean technologies (Tunnicliffe et al., 2025). Various potential ocean-based climate interventions including large-scale marine carbon dioxide removal (Oschlies et al., 2025) and ocean thermal energy conversion for low carbon power (Morrison et al., 2025), whether actioned in surface waters or on the seafloor, would have deep-ocean impacts and pose substantial risks for a rapidly changing ocean (Levin et al., 2023).

3 Managing ABNJ in their entirety as a multi-use MPA for planetary sustainability?

Roberts et al. (2025) proposed, in a Nature Comment, that the High Seas and their seabed should be protected from all extraction because such exploitation puts the “ocean's crucial role in maintaining the stability of Earth's biosphere at risk.” Stopping industrial fishing in ABNJ, for example, might be viable because it is of limited importance for wild capture fisheries overall (4.2% of global totals; Schiller et al., 2018) and the main targets such as migratory tuna are largely caught (and could be exclusively caught) in national waters. Restricting fishing to national jurisdiction waters would also support more sustainable fisheries because monitoring limitations in ABNJ and deficient legal frameworks for enforcement contribute substantially to unsustainable catches (Yuan and Han, 2025). Seabed mining could also perhaps be avoided (or at least minimized) in ABNJ because there are deep sea deposits within national jurisdictions (including of the USA; González Ortiz et al., 2023).

But achieving agreement to protect ABNJ from all extractive activities seems unlikely given political and economic drivers set in the context of demonstrated state self-interest and deference to existing IFBs. It may also be counter-productive because economic activities incentivize commercial interests to fund scientific research and to advance management approaches. This will help address the extensive knowledge gaps, ranging from climate science and fisheries to governance and human rights, in how we can protect ABNJ (Jarvis and Young, 2023). Proscribing all extractive activities would further be undesirable from a global equity viewpoint because all states have equitable rights to ABNJ under UNCLOS—and these are the only rights to marine resources that land-locked countries have (Massimi, 2024).

If complete protection of ABNJ from extractive use is not feasible (and not desirable), could we find a more appropriate (and more realistic) middle ground between the status quo and zero-extraction? “MPA” is defined by Article 1(9) of the BBNJ Agreement as “a geographically defined marine area that is designated and managed to achieve specific long-term biological diversity conservation objectives and may allow, where appropriate, sustainable use provided it is consistent with the conservation objectives” (United Nations, 2023). This is in essence what the BBNJ Agreement means for ABNJ across their entirety—as stated in Article 2 (“The 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...;” United Nations, 2023).

Recognizing the overwhelming importance of ABNJ for planetary biosphere resilience and climate stability, could we read Article 1(9) creatively and frame management of ABNJ as if they were a de facto multi-use MPA in their entirety? Treating ABNJ as a multi-use MPA within a planetary sustainability paradigm would support prioritizing conservation and sustainable use by better enabling incorporation of how necessary activities, including extraction, can be appropriately distributed and holistically managed across ABNJ, national waters, and land. A multi-use MPA management philosophy for ABNJ differs from the zero-extraction proposal by Roberts et al. (2025) in that extraction would be accepted if it does not diminish conservation outcomes and can even be desirable if, for example, it had associated infrastructure or research supporting conservation. Application of the “sustainable use consistent with conservation objectives” principle in decision-making devolved to existing IFBs (such as the ISA) and to zones within ABNJ not formally designated as MPAs would need to be part of the ongoing, flexible, and iterative development of the delivery mechanisms for the BBNJ Agreement.

Decision-making for activities (including extraction) across ABNJ as a de facto multi-use MPA could use the existing EIA provisions of Part IV of the BBNJ Agreement. Article 28(2) states that an EIA should be carried out when a planned activity in ABNJ “may cause substantial pollution of or significant and harmful changes to the marine environment” (United Nations, 2023). This risk effectively applies to any proposed activity in ABNJ if we acknowledge our extensive knowledge gaps (Jarvis and Young, 2023) and the explicit adoption by the BBNJ Agreement in Article 7(e) of the precautionary principle (“the exercise of caution in the face of uncertainty;” Singh and Ort, 2020). EIA treating ABNJ as a de facto multi-use MPA would, however, need key principles such as taking an ecocentric framing (that prioritizes conservation objectives; Retief et al., 2025) to be adopted by the Scientific and Technical Body as it develops EIA standards and guidelines as required under Article 38. There would need to be extensive work on this because, although the BBNJ Agreement has advanced EIA provisions for development decision-making (Gullett and Craik, 2025), Article 28(2) devolves carrying out EIA to the national process of the responsible Party and national EIA systems around the world have widely recognized failings (Bond et al., 2024).

How might we take forward a planetary sustainability framing and adoption of a multi-use MPA philosophy for ABNJ? This needs advocacy for adoption and arrangements for implementation (designation, monitoring, and enforcement). The BBNJ Agreement COP is the political forum at which decisions would first need to be debated and made, with the first meeting (COP1) scheduled for January 2027, and intersessional work amongst stakeholders in advance might prepare how these proposals could be considered. The “not undermine” clause of the BBNJ Agreement means broad agreement would also be needed across the existing ocean governance IFBs (such as the ISA, the IMO, and RFMOs) mainly responsible for managing activities and direct impacts across ABNJ. The priority in all decision-making for ABNJ would be conservation and sustainable use—rather than economic gain—and the planetary framing would justify only activities necessary for impacts, resources, infrastructure, or knowledge that supports outcomes assessed in balance across ABNJ and the planet. Determining conservation and sustainable use objectives and assessing impacts of potential activities and infrastructure would likely be led and coordinated by the BBNJ Agreement COP or Secretariat in association with existing IFBs. Management and enforcement arrangements might be coordinated from the BBNJ Secretariat with some level of delegation to existing IFBs.

Advocacy across ocean governance for treating ABNJ in their entirety as a multi-use MPA within a planetary sustainability paradigm could be led by the BBNJ Agreement COP and complemented by political platforms such as the High Level Panel for a Sustainable Ocean Economy. We also need to champion the importance of incorporating ABNJ considerations in terrestrial environmental governance and global action on the triple planetary crisis as part of the upcoming post-2030 sustainable development agenda. The BBNJ Agreement needs to establish itself as a focal point, not just for action in ABNJ, but for the integration of ocean sustainability with broader sustainable development and the triple planetary crisis.

4 Conclusion

Meaningful delivery of the BBNJ Agreement is threatened by ambiguities in power and scope, by effectiveness issues within wider ocean governance, and by impacts from global environmental change and activities in national waters and on land. Conservation and sustainable use within ABNJ depend on planetary sustainability and, reciprocally, offer substantial opportunities to advance global sustainable development. We should therefore consider treating ABNJ in their entirety as a de facto multi-use MPA, within a broader sustainable development context, to better enable prioritization of conservation and sustainable use (as is the aim of the BBNJ Agreement). In practice, conservation and sustainable use objectives would become the focus of all decision-making for ABNJ. Determining objectives in balance across ABNJ and the planet, assessment of potential activities and infrastructure, and monitoring and enforcement could be led by the BBNJ Agreement COP or Secretariat in coordination with existing IFBs. Adoption of a planetary sustainability framing and a multi-use MPA philosophy would need to be taken forward through the BBNJ Agreement COP and could be advocated for as part of the upcoming post-2030 sustainable development agenda because of the substantial role of the ocean in addressing the triple planetary crisis.

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Footnotes

Edited by: Sebastian Christoph Alexander Ferse, IPB University, Indonesia

Reviewed by: Mariana Piauilino Caldeira, University of Aveiro, Portugal