Global warming has left a substantial scar on Australia's Great Barrier Reef. Researchers of a new study have revealed that almost half of the corals in the most pristine part of the reef system is now dead after two successive heat waves.
Heat wave Triggered Mass Deaths Of Corals
In a new study which was published in the journal Nature on April 18, researchers said that a marine heat wave that occurred in 2016 led to catastrophic levels of bleaching that triggered the mass deaths of corals.
To gauge the extent of the damage, Terry Hughes, from James Cook University in Australia, and colleagues conducted water surveys during the widespread bleaching between March and April 2016, and again eight months later. Between March and November 2016, researchers said that the reef lost 30 percent of the corals.
"On average, across the Great Barrier Reef, one in three corals died in nine months," Hughes said.
The researchers found that many of the corals particularly those in the northern third of the reef immediately died due to heat stress. Hughes said the corals died instantly, they were essentially cooked. Others were killed more slowly. Another heat wave that hit the reef system in 2017 exacerbated the situation.
"In the aftermath of the record-breaking marine heatwave on the Great Barrier Reef in 2016, corals began to die immediately on reefs where the accumulated heat exposure exceeded a critical threshold of degree heating week," Hughes and colleagues wrote in the study.
"Fast-growing staghorn and tabular corals suffered a catastrophic die-off, transforming the three-dimensionality and ecological functioning of 29% of the 3,863 reefs. "
Global Warming To Blame
The researchers said that the increase in marine heat waves is driven by warming temperatures due to increasing amount of carbon dioxide and other planet-warming greenhouse gases in the atmosphere as a result of human activities.
"We've seen half of the corals on the Great Barrier Reef killed by climate change in just two years," said study researcher Mark Eakin, from the Coral Reef Watch of the U.S. National Oceanic and Atmospheric Administration.
"This study shows that the coral reefs that have been least affected by heat stress in the past are more sensitive to heat stress than we realized. It also shows climate change threatens the diversity that is the hallmark of coral reefs."
Eakin said that increasing marine heat waves will likely occur more frequently unless humans reduce the amount of carbon dioxide released into the atmosphere, and this could pose a significant challenge to the recovery of the reefs.