Corals are expert builders, arguably the best on the planet, though they are slow. The result of 200 to 300 million years of evolution, they grow at a snail’s pace—most expanding less than an inch a year. For example, Australia’s Great Barrier Reef, big and bright enough to be visible from space, had grown to 133,000 square miles, over double the size of Pennsylvania, and is still relatively young at about 600,000 years old.
