Scientists have reported that huge sections of Australia's Great Barrier Reef that stretch across hundreds of miles of its northern sector, have recently been found dead.
The phenomenon is largely blamed on overheated seawater largely blamed on global warming. Now, scientists report that the southerly sections around the middle of the reef are now also bleaching, which could lead to another die-off.
Terry Hughes, from the Australian Research Council Center of Excellence for Coral Reef Studies and one of the authors of a research on the Great Barrier Reef published in the journal Nature on March 15, said that they did not expect such level of destruction to the reef for another three decades.
"In the north, I saw hundreds of reefs — literally two-thirds of the reefs were dying and are now dead," Hughes said.
Hughes and colleagues conducted aerial and underwater surveys of the reef, which has undergone three major bleaching events, the worst of which happened last year. The researchers found that in the north section which experienced the hottest temperatures, hundreds of reefs experienced severe bleaching in 2016 regardless of the water quality and whether or not fishing has been banned.
Curbing overfishing and reducing pollution were thought to prevent severe bleaching, but the findings suggest these have little effect in preventing the phenomenon that kills corals at an alarming rate. The results likewise mean that even the reef's most pristine parts can be as vulnerable to heat stress as those areas that are less protected.
Saving Australia's Great Reef
Based on the findings, stopping global warming remains the best if not the only way to save the Great Barrier Reef.
"Water quality and fishing pressure had minimal effect on the unprecedented bleaching in 2016, suggesting that local protection of reefs affords little or no resistance to extreme heat," researchers wrote in their study. "Consequently, immediate global action to curb future warming is essential to secure a future for coral reefs."
Severe coral bleaching and massive die-offs of corals place the reef and the sea creatures that live near it in serious trouble. Die-offs could rob color and life from some of the most visited areas of the reef, and along with it huge amounts of income from reef tourism as the Great Barrier Reef provides about 70,000 jobs and billions of dollars in annual tourism income to Australia.
Coral reefs also serve as home to a large array of sea creatures, which means that the phenomenon is likely to make an impact on people who rely on marine creatures such as fishes for food and livelihood.
In an earlier study on declining coral reef health, Alice Rogers, from the University of Queensland, and colleagues found that a complete loss of reef complexity can result in three-fold drop in large-bodied reef fish production.
"As corals die the reef becomes flatter and less complex, which changes the interactions between reef organisms and affects the abundance of fish," Rogers said.
"That means three-times less potential catch for a fishery, which would have a huge impact on food security and peoples' livelihoods."