Australia's Great Barrier Reef has suffered the most widespread coral bleaching since its inception, scientists said on Tuesday in a terrible warning of the threat to the world's largest living organism from climate change.
Terry Hughes, a professor at James Cook University, said a comprehensive survey last month had shown that record sea temperatures had caused the third bleaching of the 2,300-kilometer reef system in just five years.
Bleaching occurs when healthy corals are stressed by changes in sea temperatures and emit algae in their tissues, causing them to lose their bright colors.
"We have surveyed 1,036 aerial reefs over the past two weeks of March to measure the extent and severity of coral bleaching across the Barrier Reef region," said Hughes.
"For the first time, strong bleach has hit all three regions of the Great Barrier Reef – the northern, central, and now much of the southern sector."
The damage came when February brought the highest monthly ocean temperatures on the Great Barrier Reef since Australia began keeping records in 1900.
The reef has an estimated $ 4 billion in annual tourism sales to the Australian economy, but is at risk of losing its coveted World Heritage status because the warmer oceans caused by climate change have damaged its health.
Back-to-back bleaching events in 2016 and 2017 prompted the government agency overseeing the reef to downgrade their long-term prospects to "very bad".
Bleaching was first observed on the reef in 1998 – the hottest year in existence – but as temperature records continue to drop, its frequency has increased, so corals have less time to recover.
Morgan Pratchett, a professor at James Cook University, said that although bleaching didn't necessarily kill all corals, some were expected to do worse than others.
More than half of the shallow water corals in the northern area of the reef died from bleaching in 2016.
"We will go underwater again later this year to assess coral losses from this recent event," said Pratchett.
(This story was not edited by NDTV staff and is generated automatically from a syndicated feed.)