In the past 30 years, the Great Barrier Reef -- Australia's iconic natural wonder -- has lost half of its coral to a combination of forces. Dr. Nancy Knowlton, Sant Chair of Marine Science at the Smithsonian Natural Museum of Natural History and Editor-in-Chief of the Ocean Portal, went on PBS NewsHour to talk about the reef, its problems, and how it can be restored. Also, read her blog post on the topic.