An extensive aerial survey of damage to Australiaâs Great Barrier Reefâthe worldâs largest coral reef ecosystemâhas revealed that mass coral bleaching is severely affecting more than 50 percent of its length and leaving patches of damages elsewhere. Scientists say climate change and a strong El Niño year have caused higher temperatures to stress coral, which puts it in danger of death. Terry Hughes, head of Australiaâs coral bleaching task force, said this is the worst bleaching event to have hit the Great Barrier Reef by far. Hughes noted that this yearâs damage is three to four times worse than previous episodesâin 1998 or 2002âadding that the âoutstanding universal valueâ of the reef is âseverely compromised.â