Rising ocean temperatures resulting from climate change are killing coral reefs across the planet. Scientists say over 70 percent of the world’s coral reefs have been exposed to the high temperatures that cause bleaching. The world's largest coral reef is Australia's Great Barrier Reef, which spans 1,400 miles and is the world's largest living structure. For the second consecutive summer, warming waters have caused extensive coral bleaching there.
March 23, 2017 video and resourse materials from PBS NewsHour.