Great Barrier Reef’s corals in steep decline

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Scientists warned climate change is irreversibly changing the Great Barrier Reef's ecosystem. AFP

Half of the Great Barrier Reef’s corals have died over the past 25 years, scientists said on Wednesday, warning that climate change is irreversibly destroying the underwater ecosystem.

A study published in the Proceedings of the Royal Society Journal found an alarming rate of decline across all sizes of corals since the mid-1990s on the vast World Heritage-listed reef off Australia’s northeastern coast.

Larger species, such as branching and table-shaped corals, have been affected hardest – almost disappearing from the far northern reaches of the reef.

“They’re typically depleted by [up to] 80 or 90 per cent compared to 25 years ago . . . They make the nooks and crannies that fish and other creatures depend on, so losing big three-dimensional corals changes the broader ecosystem,” report co-author and James Cook University professor Terry Hughes told AFP.

Aside from its inestimable natural, scientific and environmental value, the 2,300km-long reef was worth an estimated $4 billion a year in tourism revenue for the Australian economy before the pandemic.

The reef is at risk of losing its coveted world heritage status because of ocean warming – fuelled by climate change – damaging its health.

Changes in ocean temperatures stress healthy corals, causing them to expel algae living in their tissues – draining them of their vibrant colours in a process known as bleaching.