Australia has formally ratified the United Nations High Seas Biodiversity Treaty, joining an international agreement designed to protect marine biodiversity in areas of the ocean beyond national jurisdiction.

Australia deposited its instrument of ratification with the United Nations on 23 September 2026, three years after signing the agreement in 2023. The Australian Government announced the ratification on 24 September 2026. The treaty entered into force globally on 17 January 2026 and will enter into force for Australia on 23 October 2026.

Around 60 per cent of the world’s ocean lies beyond national jurisdiction, commonly known as the high seas. Until now, protecting biodiversity across these vast areas has relied on a patchwork of international agreements and organisations dealing with different activities and parts of the ocean.

Australia’s ratification coincided with another major development in national ocean policy. On 23 September, the Australian Government also unveiled the country’s first Sustainable Ocean Plan, setting out a national approach to the future management of Australian waters.

The two announcements deal with different parts of the ocean, but together they raise an important question for marine conservation. How do we protect wildlife that regularly moves between Australian waters and the high seas?

What Is the High Seas Biodiversity Treaty?

The treaty’s full name is 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. Thankfully, it is better known as the High Seas Biodiversity Treaty, or the BBNJ Agreement.

The BBNJ Agreement sits under the United Nations Convention on the Law of the Sea, or UNCLOS, which provides the broader legal framework governing the world’s oceans. It is the third implementing agreement developed under the convention and is specifically focused on the conservation and sustainable use of marine biodiversity beyond national jurisdiction.

The new treaty creates a process for establishing marine protected areas and other area based management tools beyond national jurisdiction. It also covers environmental impact assessments for activities that could significantly affect marine ecosystems, as well as marine genetic resources and the fair and equitable sharing of benefits arising from their use.

Another part of the agreement focuses on capacity building and the transfer of marine technology, particularly to developing countries. This can include sharing scientific knowledge and research, training, technical expertise and access to equipment and technology.

Importantly, the treaty does not turn the high seas into one enormous marine protected area or automatically prohibit activities such as fishing and shipping. It provides a mechanism for countries to propose and agree on conservation measures for areas that require protection.

By ratifying the treaty, Australia will be able to participate directly in those decisions once it becomes a party to the agreement.

Why This Matters to Australian Wildlife

Australia manages an enormous marine area, but many of the species found within it spend only part of their lives in Australian waters. Whales, sharks, turtles and seabirds can travel thousands of kilometres and cross repeatedly between national waters and the high seas.

That creates an obvious problem for conservation. Australia can protect habitat and regulate activities within its own jurisdiction, but migratory species may then travel beyond those waters, where different rules and pressures apply. Fishing, shipping, pollution and other activities encountered elsewhere can affect the same animals protected while they are in Australian waters.

Short tailed shearwaters are a familiar Tasmanian example. Millions return to breeding colonies around Tasmania and the islands of Bass Strait before migrating north through the Pacific to feeding grounds around Japan, Russia and Alaska. Their annual round trip can cover around 30,000 kilometres, much of it beyond waters managed by Australia. We explored this remarkable migration in more detail in The Greatest Journey on Earth.

The same applies to marine mammals. Humpback whales migrate between Antarctic feeding grounds and warmer breeding waters along Australia’s coastline, while southern right whales move between higher latitude feeding areas and breeding and calving grounds along southern Australia. Both spend parts of these migrations beyond Australian waters, so their conservation cannot rely on measures taken by Australia alone.

The High Seas Biodiversity Treaty gives countries a new way to protect important areas beyond those borders. Future marine protected areas and other conservation measures could include feeding grounds, migration routes or ecosystems used by species that also spend part of their lives in Australian waters.

That connection is what makes Australia’s participation in the treaty particularly relevant to wildlife conservation here.

Australia’s First Sustainable Ocean Plan

Alongside the treaty ratification, Australia has released its first Sustainable Ocean Plan, setting out a broader approach to the future management of its marine environment.

The plan covers Australia’s ocean from the coastline to 200 nautical miles offshore, including its external territories. It sets out a shared national vision and eight priority areas for managing the ocean and ocean economy. Climate change, biodiversity decline, pollution, marine pests, coastal development and illegal, unreported and unregulated fishing are among the pressures it identifies.

A major focus is improving coordination across jurisdictions, sectors and groups already involved in managing Australia’s oceans. Responsibility for implementing the plan is shared between ocean managers, custodians and users, with governments, industries, communities and other groups expected to lead different actions.

Implementation will be guided by a new National Ocean Steering Committee, with representatives from all levels of government, and a National Ocean Advisory Group bringing together stakeholders and expertise from outside government. Expressions of interest for membership of the advisory group are expected to open soon.

The Sustainable Ocean Plan and the High Seas Biodiversity Treaty are separate initiatives, but their timing makes them worth considering together. One deals with how Australia manages its own marine jurisdiction, while the other gives Australia a role in conservation decisions for waters beyond it.

For migratory marine wildlife, both areas are part of the same habitat.

What Happens Next?

Australia’s ratification does not immediately create new marine protected areas on the high seas. There are currently no marine protected areas or other area based management tools established or proposed under the treaty. Australia will formally become a party on 23 October 2026, when the High Seas Biodiversity Act 2026 also comes into effect and provides the domestic framework for implementing Australia’s obligations.

The first meeting of the treaty’s Conference of the Parties is scheduled for 11 to 22 January 2027 in New York, where countries will begin the next stage of putting the agreement into practice.

There are still difficult questions ahead. Proposals for new protected areas will have to pass through consultation and scientific assessment before countries decide whether to adopt them. Those decisions will involve countries with different interests and priorities, while activities including commercial fishing and shipping already operate across the high seas.

What has changed is that countries now have a global agreement specifically focused on conserving biodiversity across the high seas.

For Australia, that adds an international piece to the conservation of species that also depend on Australian waters. What happens next will determine how much difference the treaty ultimately makes for them.

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Editorial Note: This article was published on 26 September 2026. Information, legislation and external links were checked and correct at the time of publication. As implementation of the High Seas Biodiversity Treaty and Australia’s Sustainable Ocean Plan continues, details may change. This article may be updated as new information becomes available.

Cover Image by Giles Laurent / CC BY-SA 4.0.