Australia's Great Barrier Reef has suffered from its worst coral die-off ever recorded, according to a new study from the Australian Research Council Center of Excellence for Coral Reef Studies based at James Cook University. "Stress from the unusually warm ocean water heated by man-made climate change and the natural El Nino climate pattern caused the die-off," reports USA Today. At more than 1,400 miles long, Australia's Great Barrier Reef is the world's largest coral reef and the planet's biggest structure made by living organisms. In the northernmost section of the reef, which had been considered the most "pristine," some 67% of the coral died. The good news, scientists said, was that central and southern sections of the reef fared far better, with "only" 6% and 1% of the coral dead, respectively. Coral reefs result from the work of little polyps, creatures only a few millimeters long, budded on top of one another. Over centuries, the shells of these creatures combine to form the exotic shapes of coral reefs. Tiny differences in the anatomy of each polyp species affect the shape of their shells and produce the exotic shapes of each reef. The vibrant colors that draw thousands of tourists to the Great Barrier Reef each year come from algae that live in the corals tissue. When water temperatures become too high, coral becomes stressed and expels the algae, which leave the coral a bleached white color. Mass coral bleaching is a new phenomenon and was never observed before the 1980s as global warming ramped up. Besides their beauty, reefs shelter land from storms, and are also a habitat for myriads of species.