Half of the corals along the Great Barrier Reef have died in the last 25 years, prompting new warnings from scientists warning that climate change is irreversibly destroying aquatic ecosystems.
Published in the Royal Society bulletin on Wednesday, the study found a surprising rate of decline in coral of all sizes across the vast World Heritage-listed coral reefs off the Queensland coast since the mid-1990s.
Larger species, such as branched corals and table-shaped corals, were most affected and almost disappeared from the northernmost tip of reefs that experienced extreme heat stress in 2016 and 2017.
“They are usually 80 or 90 percent depleted (up to) compared to 25 years ago,” report co-author Terry Hughes of James Cook University told AFP.
“Loss of large three-dimensional corals changes a wider ecosystem, as they create corners and crevices on which fish and other creatures depend.”
Aside from its immeasurable natural, scientific and environmental value, the 2,300-kilometer-long coral reef was worth an estimated $ 4 billion annually in tourism revenue from the pre-pandemic Australian economy of COVID-19. ..
Coral reefs are at risk of losing their coveted World Heritage status due to climate change-fueled and unhealthy ocean warming.
Changes in seawater temperature stress healthy corals, expel tissue-dwelling algae, and remove bright colors in a process called bleaching.
Following a series of massive bleaching events in 2016 and 2017, the government downgraded the long-term outlook for the world’s largest organisms to “very poor.”
Massive bleaching was first seen in 1998, the hottest year on record. However, as temperatures continue to rise, their frequency increases, coral reefs shrink, and recovery becomes difficult.
“The vibrant coral population includes millions of small baby corals and many large corals, and is a big mom who gives birth to most of the larvae,” said James Cook University’s lead author. Andy Dizel says.
“Because of the small number of babies and the small number of large adults during the breeding season, their resilience is impaired compared to the past.”
Since 1995, coral reefs have been hit by several cyclones and two outbreaks of coral-eating crown-of-thorns starfish, in addition to long-term ocean warming and associated bleaching.
If a small number of starfish occur, they are considered part of the natural ecosystem. However, in the event of an outbreak, some of the coral reefs can be destroyed rapidly.
Although the latest research has covered four massive bleaching events up to 2017, the damage to coral species from bleaching in early 2020 has not yet been assessed.
This was the most extensive bleaching on record and was the first to affect the zone south of the reef.
Professor Hughes predicts that corals will continue to be extinct unless scientists meet the Paris Agreement’s promise to keep global average temperatures below pre-industrial levels below 2 degrees Celsius. He said he was.
“It takes about 10 years for the fastest-growing species to achieve a semi-decent recovery, so it will take decades during the future 6th, 7th, and 8th bleaching events as temperatures continue to rise. The chances are almost zero, “he said.
If temperatures stabilize later this century under the goals of Paris, corals are expected to be able to reconstruct and reconstruct their numbers.
Still, Hughes said, “I don’t think it will be rebuilt into a mixture of historically known species.”
If the rise is around 3 or 4 degrees Celsius, he said, “forget.”
“The orbit is changing very rapidly. We are shocked and amazed at how quickly these changes are happening. There is a change ahead.”
Climate change has wiped out half of the Great Barrier Reef’s coral reefs in the last two decades
Source link Climate change has wiped out half of the Great Barrier Reef’s coral reefs in the last two decades