The High Seas Treaty: What it is and what it means for the deep sea

A major milestone in international ocean governance was marked on 17 January 2026 when the High Seas Treaty came into force. Known formally as the Agreement under the United Nations Convention on the Law of the Sea on the Conservation and Sustainable Use of Marine Biological Diversity of Areas Beyond National Jurisdiction (BBNJ Agreement), the Treaty introduces new tools to safeguard the deep ocean’s extraordinary life and the critical services it provides.

Keep reading to learn more about the High Seas Treaty, what it means for the deep sea, challenges to overcome and opportunities for the future of ocean conservation. 

What is the ‘high seas’?

The High Seas Treaty seeks to safeguard the high seas, which comprises the ocean and deep seabed beyond any one country’s national jurisdiction (200 nautical miles beyond national shorelines). The high seas covers around two thirds of the ocean, with the deep sea making up the majority. 

The high seas is full of life and hosts incredible ecosystems, including seamounts that are hotspots of biodiversity and bustling feeding sites for larger migratory animals such as whales and sharks. The high seas is also instrumental in buffering us from the worst impacts of climate change. 

Despite their importance to the functioning of the ocean and the wider health of the planet, these fragile deep-sea ecosystems remain vulnerable to current and proposed threats such as destructive fishing practices, like bottom trawling, pollution, and deep-sea mining. The High Seas Treaty is a meaningful step towards protecting them. 

What is the High Seas Treaty?

Two decades in the making, the High Seas Treaty provides a framework to protect high seas biodiversity, strengthen ocean-climate resilience and the equitable sharing of benefits of marine genetic resources, particularly for developing countries, in waters beyond national jurisdiction. The Treaty introduces new tools to safeguard the high seas, as well as legally binding obligations for States to apply high environmental standards across ocean governance bodies, including regional fisheries management organizations (RFMOs) and the International Seabed Authority (ISA). 

António Guterres, United Nations Secretary-General, has called it a “historic achievement for people and planet, for international cooperation and the United Nations.”

The High Seas Treaty addresses four main pillars of ocean governance:

1. Area-based management tools: The Treaty forms the first ever legal framework to enable countries to establish high seas marine protected areas (MPAs). MPAs are one of several types of area-based management tools that play a vital role in reaching the global goal of protecting at least 30% of the land and sea by 2030. 
2. Environmental impact assessments: The Treaty sets obligations for environmental impact assessments (EIAs) to take place before commencing large-scale commercial activities, including deep-sea mining.
3. Marine genetic resources: The Treaty will ensure the fair and equitable sharing of benefits from the development of marine genetic resources among nations.
4. Capacity building and the transfer of marine technology: These provisions can expand independent deep-sea research, close knowledge gaps, and strengthen countries’ abilities to understand, assess and manage environmental risks. 

What does the High Seas Treaty mean for the deep sea?

The High Seas Treaty adds important new tools to the deep-sea safeguarding toolbox. The fight to protect the deep from threats such as bottom trawling, deep-sea mining and marine carbon dioxide removal demonstrate why the Treaty is so vital. 

Bottom trawling is a fishing method that involves dragging weighted nets across the seabed, which sweep up everything in their paths and damage seamounts, corals and other fragile ocean ecosystems. Together with contributing to the loss of biodiversity during the current biodiversity crisis, which has knock-on impacts on many species that rely upon seamount ecosystems, bottom trawling destroys some of the oldest life on Earth, impacts the ocean’s ability to absorb and store carbon, and releases carbon. 

While no commercial scale activity has taken place yet, deep-sea mining – the process of removing mineral deposits from the deep ocean floor – is poised to bring grave environmental, economic and social consequences. Scientists warn that biodiversity loss would be inevitable and irreversible if mining in the fragile and largely unexplored deep sea were permitted. Deep-sea mining could also risk disturbing some of the largest carbon sinks on the planet, along with the deep sea’s ability to buffer us from the worst impacts of climate change. Studies show that even after small-scale experimental deep-sea mining events, carbon cycling in the deep has still not recovered after 26 years. 

Marine geoengineering technologies are similarly under-researched. These approaches, including ocean fertilization, sinking of biomass and ocean alkalinity enhancement, seek to leverage the ocean’s natural processes to remove carbon dioxide from the atmosphere and store it in the ocean. However, any speculative benefits are offset by massive uncertainty about the environmental, economic and social impacts, and the duration for which the carbon would be stored. 

On its own, the High Seas Treaty will not stop these harmful practices, but tools such as EIAs and MPAs create a new layer of accountability and raise the bar by placing clear obligations on the international community to uphold environmental protection standards.

Challenges of the High Seas Treaty

With governance of the high seas spread over multiple institutions, including the ISA and RFMOs, the High Seas Treaty must now interact with these existing bodies and break down silos to help safeguard the ocean. Potential challenges lie in the new obligations and procedures that the Treaty will impose on existing bodies. For example, the EIAs conducted under the ISA should now be fully aligned with the Treaty’s EIA provisions, including transparency and robust monitoring. However, the ISA currently lacks baseline data, ecosystem-level understanding and long-term monitoring capacity required to meaningfully assess impacts in the deep sea, namely from deep-sea mining. Without this scientific foundation, EIAs cannot reliably predict, prevent or mitigate harm from deep-sea mining, reinforcing the need for a moratorium or precautionary pause on this harmful activity. 

A moratorium on deep-sea mining would therefore serve a dual purpose: preventing irreversible harm to ocean ecosystems while also creating the conditions necessary for the Treaty to achieve its fundamental objectives. By halting the rush to mine, States would create space to operationalize the High Seas Treaty’s tools, such as marine genetic resource benefit-sharing, capacity building, technology transfer, stronger environmental impact assessment processes,  and area-based management tools to ensure the protection and sustainable use of biodiversity in areas beyond national jurisdiction.

Opportunities for the High Seas Treaty and what’s next

The High Seas Treaty provides an unprecedented opportunity to reshape ocean governance and protect the deep sea and the incredible ecosystems it holds, in line with science, precaution and long-term sustainability. 

States must now use this momentum to bring together isolated management bodies and ensure they are acting on the global commitments laid out by the Treaty. At the ISA, this means Member States supporting a deep-sea mining moratorium and promoting formal cooperation arrangements between the High Seas Treaty Conference of Parties and the ISA Assembly and Council, including information sharing on area-based management tools and environmental impact assessments, joint scientific workshops on deep-sea mining impacts, and mutual recognition that activities in international waters must not cause biodiversity loss. At RFMOs, this means ending deep-sea bottom trawling on seamounts and other vulnerable marine ecosystems and adopting consistent conservation practices. 

The future of the deep sea, the wider ocean and the planet depends on coherent, science-based ocean governance. If we use this opportunity wisely, the High Seas Treaty will be instrumental to a better future.