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Coral bleaching on Stanley Reef,south of Townsville,which occurred in a late summer heatwave in March.Credit:Australian Marine Conservation Society/Climate Council/Harriet Spark

The federal government is under pressure at home and abroad to increase its greenhouse gas emissions cuts. A delegation from UNESCO’s World Heritage Committee and scientists from the International Union for Conservation of Nature are in Australia to inspect the reef before theyvote on downgrading its World Heritage status.

Federal and state governments are pouring billions into practical action like hand-removing the damaging crown of thorns starfish that eat coral and working with farmers to reduce water pollution.

But bleaching has become such a dominant risk to the reef it has greatly reduced the benefit of these conservation measures,said Scott Heron of the Coral Centre of Excellence at James Cook University.

“Without action on climate change the investments in reducing all other stresses will be a small drop in the ocean in terms of helping the reef,” said Dr Heron.

Dr Heron said that the governments’ conservation investment was delivering results that are “critical to help the reef survive (but) climate change is absolutely the greatest threat”.

The federal and Queensland governments have committed a total of $4 billion for reef conservation since 2019,including $580 million to improve water quality over the next decade by working with landholders to reduce erosion,sediment,fertiliser and pesticide runoff. It has committed more than $200 million to remove crown of thorns starfish and tackling illegal fishing since 2020.

University of Queensland senior lecturer Selina Ward also endorsed conservation programs,which also include “coral gardening” where hardy species of young corals are strategically planted to help repopulate damaged reef ecosystems.

She said such measures are “very helpful,but they are only on a small scale”. “The largest area ever for coral restoration project is as big as a football field.”

However,she said conservation investment would help make the reef as “healthy as possible to tackle the effects of climate change”.

Corals bleach when they are under severe stress due to high sea temperatures.Credit:Australian Marine Conservation Society/Climate Council/Harriet Spark

“It’s good work,but the people doing it will tell you unless we fix climate change those things won’t save the reef in the long term,” Dr Ward said.

The Great Barrier Reef runs for 2300 kilometres along the Queensland coast and stretches across 350,000 square kilometres.

The first mass bleaching event occurred in 1998 and there have been five in the years since,which in total have affected more than 98 per cent of the reef. The current event was caused by a late summer heatwave.

Bleaching is forecast to reduce global coral cover by 95 per cent under 2 degrees of warming,and 70 per cent under 1.5 degrees. If all countries deliver on their climate commitments the world would still be on track for 2 degrees or more of warming. If the rest of the world followed Australia’s current commitments and policies,global warming would exceed 3 degrees,according to Climate Action Tracker.

Corals turn white when they expel the algae living in their tissues,in a survival response to cope when the ocean is too hot for too long.Credit:Australian Marine Conservation Society/Climate Council/Harriet Spark

Coral bleaching occurs when the sea surface temperature is too hot for too long,causing corals to expel the algae living in their tissues and turn white. It is a sign of severe stress,but corals can recover from bleaching if sea surface temperatures fall back to normal quickly.

WWF Australia head of oceans Richard Leck said Australia should commit to climate action that was consistent with global action needed to keep global temperature rise under 1.5 degrees.

“It is a positive sign the federal government acknowledges climate change as the most significant threat to the reef but if you acknowledge the problem it’s incumbent that we take significant action to give the reef a fighting chance.”

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