The Great Barrier Reef has lost half its corals in the last 25 years: study

The Great Barrier Reef has lost half its corals in the last 25 years: study

BRISBANE: Half of the Great Barrier Reef has died in the last 25 years, with scientists warning Wednesday that climate change is irreversibly destroying water ecosystems.
A study published in the Journal of Proceedings of the Royal Society found an alarming rate of decline in all sizes of corals on the massive World Heritage-listed reef off the north-east coast of Australia since the mid-1990s.
Larger species, such as branching and table-shaped coral, have been hardest hit – virtually missing from the far northern reaches of the reef.
Co-authors and James Cook University professor Terry Hughes told AFP, “are generally (80) or 80 percent lower than they were 25 years ago.”
“They make nooks and cranes that depend on fish and other organisms, so losing large three-dimensional corals changes the broader ecosystem.”
In addition to its incomparable natural, scientific and environmental value, the 2,300-kilometer-long (1,400-mile-long) reef was estimated to cost $ 4 billion a year in tourism revenue for the Australian economy before the coronovirus epidemic.
The reef is at risk of losing its World Heritage status as the ocean warms – affected by climate change – damaging its health.
Changes in sea temperature stress healthy corals, expelling the algae that live in their tissues – they are known as bleaching.
Back-to-back large-scale bleaching incidents in 2016 and 2017 prompted the government to “very poor” the long-term outlook for the world’s largest living organism.
Mass bleaching was first seen on the reef in 1998 – at the time, the hottest year on record – but its frequency has increased as temperatures have risen, making the reef narrower and harder to recover.
The study’s lead author, Andy Dietzel, also of James Cook University, has a lively coral population of millions of small, baby corals, as well as many older people – who produce large lamas.
“Its flexibility is compromised compared to the past, as there are fewer children, and fewer reproductive adults.”
Over a long period of ocean warming and associated bleaching, the reef has been beaten by several cyclones and two outbreaks of crown-thorned starfish – which eat moong – since 1995.
When starfish are in small numbers, they are considered part of the natural ecosystem, but when there is a large outbreak, they can rapidly destroy parts of the reef.
While four large bleaching events were covered by the latest research as of 2017, damage to coral species from bleaching in early 2020 remains to be assessed.
This was the most widespread bleaching on record, marking the first time the reef has an impact on its southern reaches.
Hughes said scientists expected corals to die until the nations met their industrial commitment to maintain a rise in global average temperatures below pre-industrial levels of 2 ° C (3.6 ° F) Of.
“It takes about a decade for a half-decent recovery for the fastest-growing species, so we are likely to have decades between future sixth, seventh, and eighth bleaching events as temperatures go up and up. Are. “, He said.
If temperatures under the Paris target stabilize after this century, it is hoped that corals will be able to regroup and rebuild their numbers.
Even then, Hughes said, “We don’t think they’ll rebuild in the mix of species we’ve historically known”.
If the increase is equal to 3 or 4 ° C, “forget it”, he said.
“The trajectory is changing very rapidly, we are surprised and surprised at how quickly these changes are happening – and further changes are taking place.”

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