Global warming has killed 14% of the world’s coral reefs in a decade and more will be wiped out if oceans keep rising in temperature, a study released on Tuesday has revealed.

According to a report by the Global Coral Reef Monitoring Network (GCRMN), coral reefs equaling about 11,700 square kilometers — which is 2.5 times the size of Grand Canyon National Park — were lost between 2009 and 2018.

"Climate change is the biggest threat to the world's reefs," co-author Paul Hardisty, CEO of the Australian Institute of Marine Science, said in a statement shared by the UN.

"There are clearly unsettling trends toward coral loss, and we can expect these to continue as warming persists," he added.

The report by the United Nations-supported global data network is the largest ever survey of coral health and covers data for 40 years, among 73 countries and 12,000 locations.

The study also identifies dynamite fishing and pollution, but it is global warming that is seen as the primary reason behind the loss of coral reefs, which has left swathes of bleached skeletons in place of vibrant ecosystems.

Coral bleaching accounts for much of the loss

Corals in South Asia, Australia, the Pacific, East Asia, the Western Indian Ocean, the Gulf and the Gulf of Oman, were among the hardest hit. 

Much of the loss was attributed to coral bleaching, as per the report. 

Coral bleaching is a phenomenon that takes place when corals — under stress from warmer water—  expel the colorful algae that live inside their tissues, turning them white,

Data in the study showed that such a bleaching event in 1998 alone was responsible for the lossof 8% of the world’s corals. 

"Since 2009 we have lost more coral worldwide than all the living coral in Australia," UNEP executive director Inger Anderson said.

"We can reverse the losses, but we have to act now."

Some reefs 'bounce back'

During the study, scientists also found that there was about a 2% regain among coral reefs in 2019, indicating they can be resilient when given respite from the facets working against them.

"Some reefs have shown a remarkable ability to bounce back, which offers some hope for the future recovery of degraded reefs," Hardisty said.

Coral reefs cover just under 1% of the ocean floor but support more than 25% of marine life.  

The reefs are responsible for approximately $2.7 trillion (€2.3 trillion) annually, in goods and services, including tourism, according to the report.

dvv/jsi (AFP, Reuters)