Dreaming of someday scuba diving Australia’s Great Barrier Reef? Better move fast. Climate change is threatening what is widely considered one of the world’s natural wonders.
New research published in the journal Nature says there was a catastrophic die-off of corals on the reef during a marine heat wave in 2016.
“Averaged across the whole Great Barrier Reef, we lost 30 percent of the corals in the nine-month period between March and November 2016,” Professor Terry Hughes, director of the ARC Centre of Excellence for Coral Reef Studies in Australia, lead author of the study, said in a statement.
The northern third of the 1,430-mile-long reef was hardest hit, researchers said.
“The coral die-off has caused radical changes in the mix of coral species on hundreds of individual reefs, where mature and diverse reef communities are being transformed into more degraded systems, with just a few tough species remaining,” said co-author Andrew Baird of the center, who is, like Huges, a professor at James Cook University.
“The heat stress was worse in the northern region, and that’s where we saw the most coral bleaching and dying,” Mark Eakin, who directs the US National Oceanic and Atmospheric Administration’s Coral Reef Watch program and who was another co-author, said in a telephone interview.
The reef also experienced severe heat stress in 2017, particularly its central region, researchers said.
Nearly half the coral that once lived in shallow-water habitats across the northern two-thirds of the reef is gone, because of the two years of heat waves, researchers said.
The researchers are concerned about the possibility of a wide-scale collapse of reef ecosystems, especially if global temperature rise cannot be controlled, the statement said.
Eakin said that close to a billion people around the world rely on reefs for their main source of protein. The reefs generate tens of billions of dollars a year in recreation and tourism. They provide protection for vulnerable shorelines. And they have proved to be sources of new medicines.
The research underlines that “we have to do everything we can to reduce the impacts of climate change on these reefs or we’re going to lose most of the reefs in the future,” he said.
Some climate change models suggest that the world could lose as much as 90 percent of its reefs by mid-century, he said. “That’s why it’s so important that we deal with carbon dioxide levels in the atmosphere,” he said.
The study warned that reef collapses could be a sign of things to come.
“The large-scale loss of functionally diverse corals is a harbinger of further radical shifts in the condition and dynamics of all ecosystems, reinforcing the need for risk assessment of ecosystem collapse,” if steps aren’t taken to curb global warming, the study said.
‘‘There is no doubt that 2016 marked a step function for many of the world’s coral reefs,’’ said Kim Cobb, a coral reef expert at Georgia Tech University, who was not involved in the study. ‘‘This paper is a grim post-mortem of an event that may very well mark the beginning of the end for many iconic reefs as we know them today, at least for the foreseeable future.’’
Cobb, who witnessed a similar mass coral die-off at the Pacific island of Kiritimati in 2016, agreed that ‘‘these hardest-hit reefs will need decades to regain the level of diversity they embodied before 2016.’’
‘‘This episode should remind us that there is no reason to expect that climate change impacts should be slow and steady and predictable,’’ she wrote. ‘‘Rather, they can add up quickly to test, and in many cases exceed, critical thresholds in both human and ecological systems.’’
The Great Barrier Reef, a string of coral reefs, shoals, and islets in the Pacific off the northeastern coast of Australia, is the longest and largest reef complex in the world and an item on many people’s bucket lists.
Material from The Washington Post wire service was included in this report.