The health of the largest ecosystem on Earth is in danger. On Wednesday, UNESCO World Heritage delegates will announce whether they will place the Great Barrier Reef on a list of endangered World Heritage sites—a move the Australian government wishes to avoid. The 1,200-mile-long reef brings in billions of tourism dollars every year. Continued concerns about coastal development, particularly coal mining in Queensland, have renewed efforts to protect the reef. Some coral has been badly damaged and animal species, including dugong and large green turtles, are being threatened. According to Greenpeace, 50 percent of the reef's coral cover has been lost in the last 30 years. Reuters photographer David Gray flew to Lady Elliot Island on the southern end of the reef, capturing the following images of the tiny coral cay and surrounding shallow waters recently visited by UNESCO World Heritage delegates.