The Sahara desert, once upon a time, wasn’t a desert at all. It was green. It was a pleasant place, fed by rivers and lakes. It was home to crocodiles, hippos, turtles, and fish of all stripes. Prehistoric hunters and gatherers came to the lush land, as well, to partake of its rich bounty. It’s now the largest hot desert in the world, equal in size to the United States. Temperatures can reach upward of 130 degrees and sand dunes can climb to nearly 600 feet in height. All this begs the question: What happened? Martin Williams, in When the Sahara Was Green: How Our Greatest Desert Came to Be, helped answer this question, and asks many more. A time-traveler, of a sort, Williams went back millions of years to showcase the rich history of earth’s greatest desert. Why did its climate change? Did it really have forests roamed through by dinosaurs? How has all this impacted human populations? Will the desert ever return to that verdant Eden? And what will climate change do to the desert? He also brought to the fore the science and scientists who have come to the desert to ask more questions and find more answers in the arid heat and the deep sand. Answers, and the knowledge that even in the harshest of environments, life finds a way. Martin Williams is professor emeritus and adjunct professor of earth sciences at the University of Adelaide. His many books include Climate Change in Deserts; Nile Waters, Saharan Sands; and The Nile Basin. Buy the Book: When the Sahara Was Green: How Our Greatest Desert Came to Be (Hardcover) from Elliott Bay Books Presented by Town Hall Seattle. To become a member or make a donation click here.