# The Great Barrier Reef experienced its worst summer on record, after a rare global mass coral bleaching event impacting at least 53 countries. Bleaching occurs when marine heatwaves put corals under stress, causing them to expel algae from their tissue, draining their colour. Corals can recover if the temperatures return to normal, but they will perish if the water stays warmer than usual. Research projects are looking at breeding heat-resistant corals which can survive higher temperatures. Scientists say at the current pace of warming, 99-percent of coral reefs will simply die.
Worst summer on record for Great Barrier Reef as coral die-off sweeps planet