By Tristan Salles, University of Sydney. and Laurent Husson, National Center for Scientific Research, France When we think of coral reefs, we picture bright fish, clear water and colorful corals. But reefs have also shaped the planet in deeper ways. Our new study, published in Proceedings of the National Academy of Sciences, shows reefs have helped regulate Earth’s climate and life for more than 250 million years. They link geology, chemistry and biology into one grand planetary feedback loop.