A key consideration for the implementation of the Biodiversity Beyond National Jurisdiction (BBNJ) Agreement is managing the relationship between overlapping international frameworks and institutions. Parties to the BBNJ Agreement are required to apply and interpret the BBNJ Agreement in a manner that does not undermine other legal instrument and frameworks and that promotes coherence and coordination between the BBNJ Agreement and other legal instruments. In relation to environmental impact assessment (EIA), this requirement for coherence finds expression in article 29(4 , which provides an exception to the general obligation to conduct an EIA where the planned activity has been assessed in accordance with the requirements of another relevant legal instrument that is equivalent to the EIA provisions of the BBNJ Agreement. The equivalence exception is, however, ambiguous in the sense that equivalence is a matter of degree. Interpreting equivalence too narrowly risks redundancy and conflicting outcomes, while interpreting equivalence too broadly may render the BBNJ Agreement EIA provisions superfluous.

Understanding how EIA processes differ and determining the legal and practical implications of these differences for equivalence determinations will be an important early step in defining the role of the BBNJ Agreement’s EIA processes. This paper seeks to contribute to this understanding by conducting a comparative analysis of four EIA process that have potential to overlap with the BBNJ Agreement’s EIA process. Specifically, we examine the EIA processes under the Antarctic Environmental Protocol; the proposed EIA rules for deep seabed mining in the International Seabed Authority’s Exploitation Regulations; the environmental assessment process for marine geoengineering under the London Protocol, and fisheries assessment processes required by regional fisheries management organizations. Each process is examined with reference to the specific EIA requirements under the BBNJ Agreement to assess the degree of equivalence.  This approach allows us to develop a clearer picture of the contours of equivalence for EIA processes that apply to high seas activities and to identify areas of divergence that may require further attention by the Parties to these agreements.

We conclude the paper by commenting on the potential pathways for developing coherence and coordination of EIA processes in the high seas.

How to cite: Craik, N. and Scott, K.: Environmental Impact Assessment under the Biodiversity Beyond National Jurisdiction Agreement and the Equivalence Exception, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-713, https://doi.org/10.5194/oos2025-713, 2025.

Nearly half the surface of the Earth consists of the high seas, the ocean 200 nautical miles beyond a nation’s coastline, with a recent 2023 UN international agreement (BBNJ Treaty) requiring renewed political efforts to protect this vast area. Unique to this agreement, when ratified, will be its ability to create marine protected areas on the high seas. With various organizations and institutions beginning the race to champion their chosen biodiversity hotspot, two unique high seas oceanographic features have emerged: the Costa Rica Thermal Dome and the Sargasso Sea. In these high seas case studies, we investigate the fishing intensity, the corporate actors benefitting from the fishing effort, and shipping traffic to understand the current anthropogenic stress in both regions. We find anthropogenic activity is deeply intertwined with the biogeochemistry in these contrasting oceanographic high seas features. The Sargasso Sea is a sub-tropical gyre and is thus highly oligotrophic, while the Costa Rica thermal dome is a seasonal upwelling that brings nutrient-rich water to the euphotic zone, attracting highly migratory species and the corporate actors that aim to extract them. Understanding that the greatest current impact from anthropogenic activity on the high seas is industrialized fishing, the high seas case studies analyzed here pose the question, should we protect marine life and high seas habitat from current activity (such as in the Costa Rica thermal dome), or areas with very little anthropogenic activity that have endemic species and intrinsic natural value (the Sargasso Sea)? With the implementation of the BBNJ treaty on the horizon and limited tools to keep pace with industrial corporations who work to overexploit the high seas, it will be essential to identify the values behind the models we create to identify and champion high seas areas’ and if they are protecting marine life from harm or not.

How to cite: Carmine, G. and Halpin, P.: Protecting for or from?: Unique high-seas oceanographic features demonstrate contrasting protection priorities for the high seas , One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-904, https://doi.org/10.5194/oos2025-904, 2025.

The global ocean is critical to life on our planet and is increasingly the subject of human use. Society depends on services provided by ocean ecosystems in which ocean life plays an intrinsic part. Predicting how ocean life will respond to pressures, because of both increasing human use and impacts of climate change, is the central basis for science informed decision-making and sustainable use. At its heart this requires a comprehensive spatial understanding of the distribution of species and habitats, i.e. maps. While there have been notable efforts to develop habitat maps for the world ocean, few have been developed specifically to represent variation in biological diversity. We have developed and validated a global benthic biological habitat map for use in spatial management of the ocean. Environmental data layers (or proxies thereof) for the five most well reported drivers of marine species distributions (biogeography, water mass structure, substrate, primary production), are used in a multi-step classification process to develop two new global scale seafloor biological habitat maps. These new maps, together with existing published global and Atlantic scale habitat classifications are validated using a global benthic dataset, derived from OBIS, in a replicated Permanova analysis at the genus level. Results suggest both new models are statistically significantly better (explain more variance) than previously published benthic habitat maps. We demonstrate how these maps may be used as a decision-support tool for area-based management of the global ocean and particularly areas beyond national jurisdiction within the context of the new Biodiversity Beyond National Jurisdiction Agreement.

How to cite: Howell, K., Bridges, A., and McQuaid, K.: A biologically-validated, global-scale, benthic habitat map for use in area based management of Biodiversity Beyond National Jurisdiction, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-1198, https://doi.org/10.5194/oos2025-1198, 2025.

While the carbon cycling services that underpin the role of the ocean in climate faces prominently among the general principles of the BBNJ agreement it has been little discussed how the agreement can further the carbon sequestration of the oceans. Combining scientific findings on the processes contributing to the biological carbon pump with legal doctrinal analysis, this paper examines the potential for using the BBNJ to better integrate ocean carbon in ocean management, thereby supporting the objectives of the Paris Agreement.

The ocean, as the world’s largest carbon sink, operates through physical and biological carbon pumps. While the physical carbon pump stores carbon in seawater, and thereby increases ocean acidification, the biological carbon pump contributes to sustainable long-term carbon storage in the seabed. Without increasing acidification, the biological carbon pump transfers CO2 fixed through photosynthesis at low trophic level, via complex biological-driven processes involving various marine species to the deep ocean. There is an untapped potential for increasing these effects, by e.g. increasing marine biomass and in particular species which are central for the function of the biological carbon pump.

However, preexisting law of the sea rules on marine living resources, guided primarily by Maximum Sustainable Yield (MSY) formula, overlooks the climate benefits of marine organisms, focusing instead on maximizing catch for human consumption. Maximum Carbon Sequestration (MCS) has been suggested as a complementary management goal to MSY, aimed at optimizing carbon sequestration by maintaining high biomass levels across key species. While existing legal frameworks provided no room for such reform, the implementation of the BBNJ represents a window opportunity for integrating MCS. Examining different potential future scenarios, we propose strategies for fostering an implementation of the BBNJ which promotes the policy integration of MCS. We also suggest action points to promote biological carbon sequestration in the implementation of the BBNJ rules on marine protected areas and environmental impact assessment.

How to cite: Krabbe, N.: Promoting ocean carbon in the implementation of the BBNJ, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-1288, https://doi.org/10.5194/oos2025-1288, 2025.

The high seas, regions beyond national jurisdiction, encompass over 60% of the global ocean and serve as critical habitats for diverse marine species, including migratory whales. Many whale species, such as humpback whales, traverse multiple national waters during migration and spend substantial portions of their lives in the high seas. Humpback whales, as a cosmopolitan species, often reside in areas outside countries' Exclusive Economic Zones (EEZs) for over half of their lifetimes; in the Southern Hemisphere alone, they migrate through the waters of nearly 30 countries.

With whale protection laws varying significantly across jurisdictions, coordinating conservation efforts remains a challenge, despite international agreements like the Convention on the Conservation of Migratory Species of Wild Animals aiming to unify protection. Whale populations are particularly susceptible to ship strikes, noise pollution, and climate change, which collectively disrupt key behaviors such as feeding, breeding, and migration. As part of the Whales and Climate research program, we have studied the movements of Southern Hemisphere humpback whales in response to climate and environmental stressors. Our findings indicate notable shifts in migration timing, locations, and feeding patterns, highlighting the importance of forecasting whale movements and integrating these patterns into future conservation strategies.

Our case study evaluates current whale protection laws within both international and national frameworks, focusing specifically on Australia, South Africa, and Chile. While there is broad awareness of issues such as entanglement and vessel strikes in policy discussions, many protective measures remain insufficient or entirely absent. This gap illustrates a pronounced disconnect between scientific findings and governance. The challenge of enforcing regulations is consistent across all three nations. Finally, the study examines how the legal frameworks in Australia, South Africa, and Chile might evolve to address the dynamic challenges posed by climate change, ensuring the long-term protection of humpback whale. We advocate for a coordinated global approach to high-seas governance building on the experience from national legal frameworks to protect whale populations and the broader marine ecosystems they support.

How to cite: Meynecke, J.-O. and Huss, A.: Whales beyond jurisdictions – sentinels of the high seas, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-98, https://doi.org/10.5194/oos2025-98, 2025.

Pollution, climate change, non-renewable resource extraction, unsustainable tourism, shipping, and fishing are placing our ocean under unprecedented pressure. Areas Beyond National Jurisdiction (ABNJ), commonly known as international waters or the high seas, face significant anthropogenic pressures. While the United Nations Convention on the Law of the Sea (UNCLOS) obliges its parties to protect the marine environment, ABNJ are especially vulnerable to the impacts of overexploitation and neglect. ABNJ designation as a 'Common Heritage of Humankind'—belonging to no one yet theoretically accessible to all—has fostered a quintessential example of the ‘Tragedy of the Commons'. This tragedy is compounded by the political, financial, and logistical challenges of conducting ocean science and implementing ocean conservation measures. 

These factors, among others, have led to a historical neglect of this global commons in conservation efforts. While numerous international organizations and agreements, many stemming from the UNCLOS, exist to manage the use of ocean resources, they have been unable to prevent the current situation. The Agreement under the (UNCLOS) on the Conservation and Sustainable Use of Marine Biological Diversity of ABNJ or Biodiversity Beyond National Jurisdiction (BBNJ) Agreement arises to not only help reverse our ocean's destruction and help the world achieve The Global Biodiversity Framework's Target 3: "30X30", but through its "package deal" also offer's the Global South a path to achieve UNCLOS's provision on Promotion of the development and transfer of marine technology.¹  

To achieve the BBNJ Agreement's explicit purposes of conservation and sustainable use of biological resources in the ABNJ, an 'all-hands-on-deck' approach is required. With ABNJ comprising approximately half of the earth's surface and Global South States having 70% of the world's coastline, but limited ocean governance capacity, it is vital that Global South States are empowered to be effective partners in implementing the BBNJ Agreement.  

This paper focuses on members and partners of IUCN's efforts in Eastern and Southern Africa to increase ocean governance capacity within, between and beyond national jurisdictions. It highlights how vital it is for governments and all stakeholders to understand the ecological connectivity between the ocean that is within national territories and ABNJ. Through the Great Blue Wall Initiative this paper explains the interoperability of resources being made available through the BBNJ Agreement's provisions on Capacity Building and the Transfer of Marine Technology,² paying particular attention to the importance of achieving its provisions on needs assessments.³ Ultimately, The Western Indian Ocean region's and Africa's ability to design marine protected areas that preserve and regenerate seascapes that are diverse, resilient, and productive depends on how well capacity and technology sharing is delivered. 

Abstract word count: 42

How to cite: Raguain, J., Mossae, B., Crespo, G. O., and Pouponneau, A.: The BBNJ Agreement and the Great Blue Wall: Unlocking Ocean Conservation and Capacity for Africa , One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-1353, https://doi.org/10.5194/oos2025-1353, 2025.

How to cite: Karan, B.: Bridging Boundaries: Implementing the BBNJ Agreement in the Mediterranean Sea and Its Synergies with the Barcelona Convention, One Ocean Science Congress 2025, Nice, France, 3–6 Jun 2025, OOS2025-434, https://doi.org/10.5194/oos2025-434, 2025.