Photo Gallery: Threats Mounting to Great Barrier Reef 05/21/2013
 In just the last 27 years, Australia's Great Barrier Reef has lost half of its...
DPA

In just the last 27 years, Australia's Great Barrier Reef has lost half of its coral. And the future doesn't look much brighter. Global warming is a threat as is Australia's booming extraction industry. UNESCO is considering placing it on its "in danger" list.