Half of the corals on Australia’s Great Barrier Reef have died out over the past 25 years, scientists warned on Wednesday that climate change is incredibly destroying the World Heritage-listed underwater ecosystem.
A study published in the Proceedings of the Royal Society Journal found an alarming rate of decline in corals of all sizes on the vast rocks along the country’s northeast coast since the mid-1990s.
Large species such as branches and table-shaped corals are most affected – almost disappearing from the northern border of the throat, the researchers said.
Terry Hughes, a co-author of the report and a professor at James Cook University, told the AFP news agency: “They’re usually down (up to 50 per cent) or less than 25 years ago.
“They make nooks and crannies that depend on fish and other animals, so losing large three-dimensional corals changes the wider ecosystem.”
In addition to its natural, scientific and environmental value, the 2,300-kilometer (1,400-mile-long) reef was worth about 4 4 billion a year in tourism revenue for the Australian Australian economy before the coronavirus epidemic struck.
The rock is in danger of losing its famous World Heritage status due to ocean warming fueled by climate change, which is detrimental to its health.
Changes in ocean temperature stress healthy corals, causing them to expel algae from their tissues and from their living colors in a process known as bleaching.
Back-to-back mass bleaching events in 2016 and 2017 prompted the government to downgrade the long-term outlook for the world’s largest living organism to “very poor.”
Mass bleaching was first seen on the reef in 1998 – the warmest year on record at the time – but its frequency has increased as temperatures have risen, making it difficult for the reef to recover from each event.
“Vibrant coral populations have millions of small, baby corals, as well as many large ones – big uncles that produce most larvae,” said Andy Diesel, lead author at James Cook University.
“Its resilience has been compromised compared to the past because there are fewer children and fewer large breeding adults.”
On top of the long-term sea temperature and associated bleaching, the reef has been infested with many cyclones and crown-prickly starfish that eat coral since 1995.
Our latest research published today shows the transformational changes # GreatBarrier Reef In the last 25 years – almost every coral species has declined, the species mix has changed, the size of the colony is smaller, and there are fewer juveniles. https://t.co/YPL5yW1GTy AD_ADietzel https://t.co/YKlx2lSAvc
– Terry Hughes (@ Professional Hughes) October 14, 2020
When starfish occur in small numbers, they are considered part of the natural ecosystem, but when a large outbreak occurs, they can quickly destroy parts of the reef.
While recent research has covered four mass bleaching events to 2017, the damage from bleaching to coral species in early 2020 has yet to be assessed.
It was the most extensive bleaching on record, affecting the southern parts of the reef for the first time.
Hughes said scientists expect nations to die unless they accept the Paris Agreement’s commitment to keep their global average temperature below 2 degrees Celsius (6.6 degrees Fahrenheit) above pre-industrial levels.
“Semi-civilized recovery for fast-growing species takes about a decade, so we are likely to find decades between future sixth, seventh and eighth bleaching events as temperatures rise and rise and fall,” he said. .
If temperatures stabilize by the end of this century under the Paris target, hopefully corals will be able to regroup and regenerate their numbers.
Even then, Hughes said: “We don’t think they’ll rebuild the species into a mix of historically known species.”
If the rise is three or four degrees Celsius, “forget it,” he said.
“This path is changing very fast – we are amazed and amazed at how fast these changes are happening – and there is change ahead.”