SYDNEY • The Great Barrier Reef is being given an A$500 million (S$502 million) boost by Australia in the battle to save the world's largest living structure as it faces mounting challenges such as climate change, agricultural run-off and a coral-eating starfish.

"Like reefs all over the world, the Great Barrier Reef is under pressure," Prime Minister Malcolm Turnbull said in a statement yesterday, calling the funding the largest granted to the famous tourist icon.

"A big challenge demands a big investment - and this investment gives our reef the best chance."

Mr Turnbull said the funds would go towards improving water quality, tackling predators and expanding restoration efforts.

The site, which attracts millions of tourists, is reeling from significant bouts of coral bleaching due to warming sea temperatures linked to climate change.

It is also under threat from the coral-eating crown-of-thorns starfish, which has proliferated due to pollution and agricultural run-off.

Earlier this month, scientists said the site suffered a "catastrophic die-off" of coral during an extended heatwave in 2016, threatening a broader range of reef life than previously feared.

A study in the journal Nature said some 30 per cent of the reef's coral perished, the first of an unprecedented two successive years of coral bleaching along the 2,300km reef.

The reef is a critical national asset, contributing A$6.4 billion a year to the Australian economy. Canberra has previously committed more than A$2 billion to protect the site over the next decade, but has been criticised for backing a huge coal project by Indian mining giant Adani nearby.

The Great Barrier Reef, which can be seen from space, covers 348,000 sq km and was put on the World Heritage list in 1981 as the most spectacular coral reef on the planet, according to the website of the United Nations cultural body Unesco.

Unesco considered putting it on the "in danger" list last year due to recent widespread destruction but voted against it, allowing Australia's conservative government to dodge political embarrassment and potential damage to the country's tourism industry.

BLOOMBERG, AGENCE FRANCE-PRESSE, REUTERS