World court rules countries must protect oceans by reducing fossil fuel emissions as island states fight for survival.

The tribunal found (PDF) that signatories to the UN Convention on the Law of the Sea’s responsibilities to prevent marine pollution extend to greenhouse gas emissions, which harm oceans by altering the earth’s atmosphere.

The island states had asked the court to clarify what was considered marine pollution under the convention, amid rising oceans, soaring ocean temperatures and ocean acidification caused by fossil fuels and other greenhouse gas emissions.

Gaston Browne, the prime minister of Antigua and Barbuda, one of the countries that brought the case, said small island nations were “fighting for their survival” due to the emissions of big polluters.

“Some will become uninhabitable in the near future because of the failure to mitigate greenhouse gas emissions,” he said. “We demand that the major polluters respect international law and stop the catastrophic harm against us before it is too late.”

The 1994 convention, signed by 169 countries, already provides the legal basis for countries to protect the marine environment from polluting substances, including oil from ships, but the tribunal’s decision acknowledges that atmospheric emissions are also harming oceans.

The tribunal ruled that states had an obligation to act, noting “the high risks of serious and irreversible harm to the marine environment”.

The Commission of Small Island States on Climate Change and International Law (COSIS), which brought the case on behalf of nine countries, hailed the advisory opinion from the world court as a “tremendous legal victory”.

“[The court made] history by delivering the first ever advisory opinion on climate change and oceans,” COSIS said.

Island countries have fought for more decisive action on climate change for decades and battled disinformation spread by fossil fuel companies.

The nine states that joined the COSIS case are Antigua and Barbuda, Niue, Palau, St Kitts and Nevis, St Lucia, St Vincent and the Grenadines, Tuvalu and Vanuatu, which last year experienced two Category 4 storms within 24 hours.

In addition to more severe and frequent storms, island states are also facing more gradual changes from climate change, such as the loss of vegetable gardens when salty seawater mixes with groundwater.

Eselealofa Apinelu, representing the South Pacific island of Tuvalu, said Tuesday’s opinion made clear that all states were legally bound to protect the marine environment, and other states, from the existential threats of climate change.

She called it “an important first step in holding the major polluters accountable”.

The ITLOS case is just one of several ongoing international efforts to address fossil fuels polluting oceans.

Dirty bunker fuels used by cargo ships have been coming under increased scrutiny by the International Maritime Organization (IMO), while a planned Global Plastics Treaty will address plastics and microplastic pollution.