Australia's Great Barrier Reef has evolved over hundreds of thousands of years and is the world's largest reef ecosystem. It is also among the most endangered, having lost half its coral cover in the last quarter century. While scientists fear that rising sea temperatures will irrevocably harm the Great Barrier Reef, as VOA's Rosanne Skirble reports, a new study charting its climate history finds that corals have survived and adapted to great fluctuations in the past.