Australia's Great Barrier Reef is in very poor condition because of climate change, over-fishing and land clearing, a state agency said on Friday, as it downgraded the reef's status to the lowest level, which could jeopardize its World Heritage status.

The Great Barrier Reef Marine Park Authority (GBRMPA) said the health of the world's largest coral reef system, off the northeast coast of the Queensland state, had deteriorated since its last review in 2014, but the problems the reef faces were not insurmountable.

"The long-term outlook for the Great Barrier Reef is very poor - that's largely driven by climate change," GBRMPA's Chief Scientists David Wachenfeld told reporters in Sydney. "With the right mix of local actions to improve the resilience of the system and global actions to tackle climate change in the strongest and fastest way possible, we can turn that around."

The report, which is compiled every five years, painted a deteriorating picture of widespread coral bleaching, habitat loss and ­degradation caused by human-induced climate change, overfishing, poor water quality, and coastal land clearing for grazing.