More than a dozen of the coral islands that mark Australia’s maritime boundaries are at risk of disappearing, a study has found.

Multiple stresses including rising sea levels threaten their existence.

Their disappearance could have implications for the country’s maritime borders, the study said.

The islands extend the jurisdiction of Australia, with over a million square kilometres of its territory supported and demarcated by their presence.

The study assessed 56 islands based on factors including how vulnerable they are to heatwaves and being flooded.

The report, which was published in the Science of the Total Environment journal, identified three islands on Western Australia’s North West Shelf that were considered at “very high risk” of climate threats.

Eleven more islands in the Coral Sea off the Queensland coast were classed as facing high risk.

None of the islands had zero risk.

The risk assessments were based on the current conditions the islands endure, but the report said the threat of marine heatwaves and rising oceans will increase due to climate change.

The study said the risk to the islands has implications for the communities that live and rely on them. It said the risk of their disappearance also has geo-political implications.

The islands “provide large amounts of area that Australia has rights over – fishing, transport, mineral exploration,” Dr Thomas Fellowes, of the University of Sydney, told the BBC.

Dr Fellowes – who co-wrote the study – said Australia’s coastal management depends on the survival of the coral islands.

He said taking steps to reduce fossil fuel usage could help slow the decline of island decay.

Coral islands are low-lying land masses composed of the sediments produced by coral debris.

Coral is under threat in Australian waters.

The Great Barrier Reef has lost more than half of its corals due to climate change, including mass bleaching events – a phenomenon where corals under stress drive out the algae that give them their distinctive colours.

Approximately 25% of the world’s marine species are dependent on coral reefs at some point in their life cycle.