SYDNEY - Australia’s plan to rescue the beleaguered Great Barrier Reef has been set back at least two decades after the fragile ecosystem suffered its worst-ever bleaching last year, experts said Friday.

The vast coral reef - which provides a tourism boon for Australia - is under pressure from agricultural run-off, the crown-of-thorns starfish, development and climate change. Last year swathes of coral succumbed to devastating bleaching, due to warming sea temperatures, and the reef’s caretakers have warned it faces a fresh onslaught in the coming months.

Canberra updated the UN’s World Heritage committee on its “Reef 2050” rescue plan in December, insisting the site was “not dying” and laying out a strategy for incremental improvements to the site. But an independent report commissioned by the committee concluded that the government had little chance of meeting its own targets in the coming years, adding that the “unprecedented” bleaching and coral die-off in 2016 was “a game changer”.

“Given the severity of the damage and the slow trajectory of recovery, the overarching vision of the 2050 Plan... is no longer attainable for at least the next two decades,” the report said.

Last year’s bleaching killed two-thirds of shallow-water corals in the north of the 2,300-kilometre (1,400-mile) long reef, although central and southern areas escaped with less damage.

The government has pledged more than Aus$2.0 billion (US$1.5 billion) to protect the reef over the next decade, but researchers noted a lack of available funding, with many of the plan’s actions under-resourced.

The latest assessment comes after the Great Barrier Reef Marine Park Authority warned the Queensland State government of an “elevated and imminent risk” of mass-bleaching this year, the Australian Broadcasting Corporation reported.