The Great Barrier Reef's massive loss to coral bleaching last year might have been just a taste of things to come. According to a study by a team of marine scientists, 99 percent of the world's coral reefs could undergo severe coral bleaching before the century ends. The culprit? Climate change. When sea water in a certain location turns warmer than usual, corals in that area expel the algae living in their tissues, effectively turning them white. That's what bleaching is. It doesn't instantly kill the corals, but it makes them much more vulnerable to fatal diseases.