Can you put a price on coral reefs under threat from climate change? The BBC's Phil Mercer reports from Australia, where the fate of the Great Barrier Reef has sparked debate over the merits of conservation and tourism. Manuela Saragosa speaks to Professor Nick Graham of Lancaster University's Environment Centre about the economic arguments for conservation, and Kathy Baughman McLeod, managing director of climate risk and investment at The Nature Conservancy, about an insurance policy for coral reefs. (Photo: A coral reef in the Red Sea, Credit: Getty Images)