The Great Barrier Reef, one of the world’s most valuable habitats, has lost half of its coral populations in the last quarter of a century, a decline that Australian researchers say will continue unless drastic action is taken to mitigate the effects of climate change.
The researchers studied coral colonies along the reef between 1995 and 2017 and found that almost every coral species has declined.
The size of the colonies was smaller; there were fewer “big moms” or older big corals that produce baby corals; and there were fewer of these babies that were vital to the reef̵
“Our results show the ability of the Great Barrier Reef to recover – its resilience – is compromised compared to the past, as there are fewer babies and fewer large breeding adults,” said Dr. Andy Ditzel, lead author of the study. . in a statement.
The study was published Wednesday in the journal Proceedings of the Royal Society.
Dr. Dietzel and other researchers at the ARC Center for Excellence in Coral Reef Research in Queensland, Australia, measure changes in colony size as a way to understand the ability of corals to reproduce.
Bleaching – a process in which corals shed algae and turn white with increasing water temperature – contributed to large losses of coral colonies in the northern and central Great Barrier Reef in 2016 and 2017. The southern part of the reef was also exposed to record temperatures in the beginning by 2020, according to researchers who cite climate change as one of the main drivers of reef disruption.
“There is no time to waste,” the researchers said in a statement. “We need to drastically reduce greenhouse gas emissions as soon as possible.”
“We once thought that the Great Barrier Reef was protected by its huge size, but the results show that even the largest and relatively well-protected reef system in the world is increasingly compromised and in decline,” said one of the researchers, Terence Hughes. declaration.
The decline of “branching and coral-like corals,” which provide critical habitats for fish, is particularly pronounced, the researchers said.
“They were hardest hit by record temperatures, which caused massive bleaching in 2016 and 2017,” said Professor Hughes.
“The changes in Reef are shocking,” he added on Twitter.
He complained about the lack of attention to the study by government leaders in Australia, the world’s largest coal exporter. The government has opposed calls to reduce carbon emissions, even as heat waves, droughts and fires continue to expose the country’s vulnerability to climate change.
The Great Barrier Reef, which maintains a wide range of marine life, has between 300 and 400 coral species and stretches for thousands of kilometers along the Australian coast.
“You can literally see it from space,” said Deron Berkepile, a professor in the Department of Ecology, Evolution and Marine Biology at the University of California, Santa Barbara.
Coral reefs worldwide are responsible for billions of dollars in tourism and provide habitat for fish that feed nearly one billion people on the planet, he said.
The Australian researchers’ findings are important, he said, as they focused on the reef’s reproductive capacity and its ability to recover from the devastating bleaching events caused by man-made climate change.
“The situation is terrible,” said Professor Berkpeil.
But people should not feel hopeless about the future of coral reefs, he said, even as they wait for world leaders to take more aggressive steps to limit the effects of climate change.
At the local level, for example, nitrogen pollution – which enhances bleaching – can be controlled by softening fertilizers and effluents, according to a study by Professor Burkepile with other researchers at his university.
“The other thing we need to remove is that coral reefs are incredibly resilient,” he said. “If we don’t damage them all the time, they will recover.”
Kitty Bennett contributed to the research.