16 March 2017, The Conversation, Year-on-year bleaching threatens Great Barrier Reef’s World Heritage status. The Great Barrier Reef has already been badly damaged by global warming during three extreme heatwaves, in 1998, 2002 and 2016. A new bleaching event is under way now. As shown in a study published in Nature today, climate change is not some distant future threat. It has already degraded large tracts of the Great Barrier Reef over the past two decades. The extreme marine heatwave in 2016 killed two-thirds of the corals along a 700km stretch of the northern Great Barrier Reef, from Port Douglas to Papua New Guinea. It was a game-changer for the reef and for how we manage it. 
Bleaching caused by extreme heat in summer 2016, based on extensive aerial surveys. Category 4 in red: 60-100% of colonies were bleached; Category 3 in orange: 30-60% bleached. Author provided Our study shows that we cannot climate-proof coral reefs by improving water quality or reducing fishing pressure. Reefs in clear water were damaged as much as muddy ones, and the hot water didn’t stop at the boundaries of no-fishing zones. There is nowhere to hide from global warming. The process of replacement of dead corals in the northern third of the reef will take at least 10-15 years for the fastest-growing species. The Great Barrier Reef is internationally recognised as a World Heritage Area. In 2015 UNESCO, the world body with oversight of World Heritage Areas, considered listing the reef as a site “in danger” in light of declines in its health. Australia’s response falling short. Read More here