Fifth mass coral bleaching event at Australia's Great Barrier Reef

The Great Barrier Reef, a 2,300 kilometer (1,400 mile) long expanse of tropical corals, is under threat due to repeated mass bleaching events. According to Environment Minister Tanya Plibersek, climate change is identified as the biggest threat to coral reefs worldwide, including the Great Barrier Reef, which is a UNESCO World Heritage site. Mass bleaching occurs when corals are heat-stressed and expel the algae that gives them life and color. This event has been detected five times at the Great Barrier Reef, with only two mass bleaching events recorded prior to 2016.