The Great Barrier Reef’s recent El Nino-triggered mass coral bleaching could threaten its world heritage status, scientists and conservationists have warned.

Last year, the United Nations’ World Heritage Committee decided not to put the reef on its “in danger” list, which could have been potentially disastrous for the tourism industry.

But footage released this week revealed brightly bleached white reefs along Queensland’s far north coast.

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The United Nations Educational, Scientific and Cultural Organisation (UNESCO) website states that if progress is not made, their decision would be reviewed at its session in 2017.

Janice Lough, a scientist with the Australian Institute of Marine Science and member of the National Coral Bleaching Taskforce, said the current situation looked “very bad” in the northern part of the Great Barrier Reef.

“Water temperatures have been really well above normal for several weeks now and, as we see from the vision, large parts of the reef have been affected,” Dr Lough said.

“I think they only found evidence of four reefs without coral bleaching in the far north.”

When the committee decided not to list the reef as “in danger”, it recommended Australia update it on its progress to improve reef and water quality.

The federal government had previously highlighted to UNESCO the fact that the northern part of the Great Barrier Reef was in pristine condition.

UNESCO will be watching this disaster with great alarm: WWF

But Richard Leck, from the World Wildlife Fund, which provides advice to the heritage committee, said now the northern part of the reef had been severely bleached, it was at risk of coral mortality.

“I’m certain that UNESCO and the committee will be watching this disaster unfolding with great alarm,” Mr Leck said.

“I think it’s early days to see how they will respond, but the first question I’m sure they will have is ‘how does this affect the world heritage values of the reef?'”

Dr Lough said she was saddened to think that could become a reality.

“I think it’s a real possibility,” she said.

“The north part of the reef has been what we would call the most pristine part, less affected by human impact.”

Dr Lough said it was still too early to tell what percentage of the severely bleached coral would die, and said scientists would monitor the reef system closely for the next several months.

She said it was important that no other major events, such as a cyclone, struck the far north region over the coming years, so that the reef had time to recover and rebuild.

A spokesman for Environment Minister Greg Hunt said the government would provide an update on the implementation of its Reef 2050 Plan to the World Heritage centre mid next year.

“We have already briefed senior officials 18 months ahead of schedule and our implementation plan is also ahead of schedule,” he said.

“The next state of conservation report is due for consideration in mid-2020.

“This is part of the normal five-yearly reporting cycle for world heritage properties.”

Mr Hunt’s spokesman said the government was monitoring the situation in the northern area of the reef.

“The extent of the bleaching in the northern third of the reef is of concern, and we are continuing to monitor the situation closely through a combination of community and industry partnerships, rigorous science and advanced technology,” he said.

-ABC