With coral reefs being among the ocean’s most threatened ecosystems, a previously unknown find 30 meters (100 feet) deep delivers hope for better protection from global warming. A “pristine” 3-kilometer (2-mile) coral reef was discovered by marine explorers off the coast of Tahiti. Dr. Julian Barbiere, from UNESCO, said there were probably many more of these ecosystems "we just don't know about". "We should be working to map them and to protect them." "We know that about 25% of marine species can be found in coral reefs," he said. "So the next stage is to find what species live around this type of reef." French underwater photographer Alexis Rosenfeld said it had been "magical to witness giant, beautiful rose corals stretching as far as the eye can see".