Photograph by Steve Ruddy, My Shot

Some living coral reefs probably began growing more than 50 million years ago. Today all reefs are an important part of the planet that many species depend on—including some 500 million humans. Reefs provide food for millions of people, protect coastlines from erosion, yield new medicines, and even stoke the engines of commerce. NOAA estimates that reefs contribute nearly $30 billion to the global economy each year.