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The Great Barrier Reef is changing. Why isn't it on UNESCO's 'in danger' list?

UNSW Sydney

Key Facts:

A UNESCO draft decision will keep the Great Barrier Reef off its ‘in danger’ list. Meanwhile the Reef keeps changing as ocean temperatures continue to rise.

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The Great Barrier Reef has again avoided being placed on UNESCO's list of World Heritage in Danger, five years after Australia successfully opposed an earlier recommendation it be placed on the list.

The draft decision, now before this week's World Heritage Committee meeting in Busan, South Korea, recognises Australia's investment in reef management while also expressing grave concern over repeated mass bleaching, deteriorating ecological conditions and the continuing impacts of climate change.

The world's oceans have just experienced their hottest June on record. Marine heatwaves are also becoming more frequent, and the Great Barrier Reef has suffered through six mass bleaching events in less than a decade.

The draft also calls for further reporting on the Reef's most recent bleaching event in 2025 and Australia's progress on improving water quality.

While the Committee can still amend the recommendation in the next few days, UNSW Professor Lucas Lixinski, an expert in international law and World Heritage, says whatever the final wording, the underlying questions about the Reef's future remain.

“It's not that it resolves the issue,” Prof. Lixinski says.

“It just says, 'In a few years, we're going to revisit this.'”

Corals experience extremes, not averages

“While the high global average gives us a very broad picture, a coral really only cares about the temperature at its own reef,” says UNSW Professor Alex Sen Gupta, an expert in marine heatwaves.

Corals bleach when water temperatures stay above their local tolerance. If heat stress is intense or prolonged, bleaching can lead to coral mortality.

“The coral doesn’t experience the average,” Prof. Sen Gupta says.

As the climate warms, those damaging temperatures become more likely.

Prof. Sen Gupta describes this as “loading the dice”, where each increment of warming increases the likelihood of the prolonged heat that can trigger coral bleaching.

“The whole temperature distribution is shifting upwards, so we are seeing extreme heat more often,” he says.

A changing Reef

Before a mass bleaching event in 2024, coral cover had risen to high levels across many parts of the Great Barrier Reef, driven mostly by fast-growing Acropora corals.

But coral cover is only one measure of reef condition. It doesn’t show the diversity or composition of the coral community, or how vulnerable that community may be to the next disturbance.

“The headline figure can be high coral cover, while the underlying coral community itself has degraded substantially,” Prof. Sen Gupta says.

Those fast-growing corals can recolonise quickly after a disturbance, but many are also highly susceptible to marine heatwaves, cyclones and crown-of-thorns starfish.

“High coral cover does not mean the Reef has returned to the same ecological state,” Prof. Sen Gupta says.

“Fast-growing corals can rebuild more quickly, but they are also among the first lost when heat stress returns.

“Eventually temperatures could get too high for these species to recover.”

UNESCO measures stewardship

“When a country nominates a site for World Heritage listing, it's effectively saying ‘this place has outstanding universal value’,” Prof. Lixinski says.

“It's recognising that this place matters not just to one country, but to humanity.”

UNESCO adopted the World Heritage Convention in 1972, with the international treaty founded on the idea that some places are too important to belong to one nation alone.

The Convention provides the framework for protecting sites of outstanding universal value – it is not a direct scientific index of ecosystem health. The Committee considers scientific advice alongside whether governments are acting as appropriate stewards.

“We're trying to protect those sites from ourselves,” Prof. Lixinski says.

Human-caused climate change is now testing whether the Convention that was built to protect exceptional places can respond to a planetary-scale threat.

Why the list matters

The World Heritage system has evolved over five decades from a largely expert-led conservation process into one operating at the intersection of science, law and international diplomacy. Scientific advice informs the process, but the final decision rests with member states.

“I don't necessarily see a problem with it being political,” Prof. Lixinski says.

“The problem is pretending it's neutral and purely scientific.”

He says an 'in danger' listing isn’t saying a place is ecologically collapsing.

“That's not what it was designed to do,” he says.

“The ‘in danger’ list was actually meant to be a place for help.”

Originally intended to mobilise expertise and international assistance for threatened sites, the ‘in danger’ list has increasingly become viewed as a measure of national environmental performance – not an invitation for support.

“It has become a bit of a badge of shame,” Prof. Lixinski says.

“An ‘in danger’ listing would actually be beneficial to the environment. It attracts more funding and invites more accountability.

“But it would be shameful for the Australian Government.”

The limits of management

UNESCO looks to the International Union for Conservation of Nature for independent scientific advice and then assesses whether governments are acting as appropriate guardians. This includes considering local actions that improve resilience – improving water quality, controlling crown-of-thorns starfish and restoring damaged reefs.

But even the best-managed reef can’t escape a warming ocean.

Prof. Sen Gupta says while local management can build resilience, it cannot remove the dominant threat of climate change.

“Reducing local pressures from poor water quality and crown-of-thorns starfish predation can give coral communities a better chance to persist and recover from disturbance,” he says.

“But corals still have physiological limits. If heat stress exceeds those limits, local management cannot prevent their mortality.

“The overarching threat to coral reefs is global warming.”

He says restoration can still be valuable at selected, high-priority sites, but cannot realistically offset climate-driven losses across the entire Great Barrier Reef.

“The scale of the Reef means restoration has to be targeted,” Prof. Sen Gupta says.

“It can support particular reefs or valued sites, but it is not a substitute for reducing greenhouse gas emissions.”

What happens next?

The Reef’s prospects in a warmer future depend on both local stewardship and decisions made far beyond the boundaries of the World Heritage Area.

Prof. Sen Gupta says while Australia cannot stabilise the climate on its own, its choices still matter.

Climate change presents what he says is a classic “tragedy of the commons” – a collective-action problem where no single country can stabilise global temperatures alone, yet every additional reduction in emissions helps limit future warming.

“That makes rapid, sustained reductions in global greenhouse gas emissions the central long-term response,” Prof. Sen Gupta says.

“We understand the cause and we know what has to happen: greenhouse gas emissions need to fall rapidly.

“The challenge is turning that knowledge into action at the scale and speed required.”

Contact details:

Melissa Lyne, UNSW News & Content

E: [email protected]