Guardian Australia environment reporter Graham Readfearn talks about the sixth mass coral bleaching event at the Great Barrier Reef in Queensland, which occurred earlier this year. He describes his visit to the John Brewer Reef near Townsville and what he has learned about the causes of the Great Barrier Reef's decline. We learn about its current condition and the reef's future in the face of climate change and other factors. Graham also explains what happened during the recent assessment of the reef's condition by a scientific team from UNESCO. Will the Great Barrier Reef finally be placed on the World Heritage 'in danger' list?