Global heating has pushed the world’s coral reefs to a fourth planet-wide mass bleaching event that is on track to be the most extensive on record, US government scientists have confirmed.
Some 54% of ocean waters containing coral reefs have experienced heat stress high enough to cause bleaching, the National Oceanic and Atmospheric Administration’s Coral Reef Watch said.
The first global bleaching event happened in 1998 with 20% of the ocean’s reef corals exposed to a level of heat stress high enough to cause bleaching. The second event, in 2010, saw 35% reaching that threshold, and the third from 2014 to 2017 peaked at 56%.