An underwater heat wave that damaged huge sections of Australia’s Great Barrier Reef two years ago spurred a die-off of coral so severe that scientists say the natural wonder will never look the same again.

Scientists said nearly one-third of the reef’s coral were killed when ocean temperatures spiked in 2016, a result of global warming, according to a study published Wednesday in the journal Nature.

The damage to the reef, one of the world’s largest living structures, has also radically altered the mix of its coral species, scientists said.

“The reef is changing faster than anyone thought it would,” said Terry P. Hughes, the lead author of the study and the director of a government-funded center for coral reef studies at James Cook University in Queensland.

“One thing we can be sure about is the reef isn’t going to look the same again,” Professor Hughes said.

The reef is home to thousands of species, including sharks, turtles and whales. Australia relies on it for about 70,000 jobs and billions of dollars annually in tourism revenue, all now threatened by years of accumulated damage.

The study’s authors estimated how much coral had died in the immediate aftermath of the 2016 heat wave, and then returned nine months later to discern how many corals had regained their color — a sign of restored health — and how many had died. Their report describes a catastrophic die-off on the northern part of the reef, impacting the mix of coral species.  Read on