The Great Barrier Reef in Australia appears to be in the beginning of yet another widespread bleaching event due to heat stress, according to a report from the National Oceanic and Atmospheric Administration. 

The Great Barrier Reef also experienced mass bleaching events in 2016 and 2017. 

The reef is the largest living structure on the planet, and has been named a World Heritage site by UNESCO, in part for its rich biodiversity. 

Across the world coral reefs are dying, and coral bleaching events are becoming more common, in part because climate change is heating the world’s oceans. Warmer waters are a cause of coral bleaching. Carbon dioxide emissions can also drive coral bleaching through a process called ocean acidification, which occurs when carbon dioxide dissolves in ocean waters and turns into carbonic acid.

Bleaching does not mean a coral will die, but it puts it at a higher risk of death. Half of all the corals in the Great Barrier Reef died after the 2016 bleaching event, according to the Atlantic. Generally, coral reefs take 15 to 25 years to recover from a bleaching event, according to UNESCO. 

As a result, successive bleaching events can irrevocably derail the recovery process. 

The UN has previously warned that if the world hits 2 degrees Celsius of warming above pre-industrial levels, over 99% of the reef will die. 

The Great Barrier Reef is worth over $50 billion to the Australian economy, and the country is already suffering from other climate change-fueled disasters, including the widespread bushfires that occurred late last year. 

Worldwide, UNESCO estimates that the loss of coral reefs due to climate change could amount to $500 billion each year by 2100, with people who rely on the reefs for daily subsistence being hit the hardest.