No one would challenge the majesty of Australia's Great Barrier Reef. Nearly 1,500 miles long, the reef is alight with a kaleidoscope of vivid colours. It's home to roughly 9,000 species of fish, molluscs, whales and other creatures. In 1981, the reef was designated a UNESCO World Heritage Site, a status that helps it draw 2 million visitors a year. It's also dying. At our own hands. Two major bleaching events have wracked the Great Barrier Reef over the last two years, leaving chunks of it dead.