“I never imagined, when I first embarked on this journey into the heart of the desert, that I would still be seeking answers to these same questions a half century on.”
—From When the Sahara Was Green
is a stark landscape of sand and sky, the largest hot desert in the world once comprised roughly 5.9 million square kilometers of verdant tropical savannas and grasslands. In this engrossing book, Williams, an earth sciences emeritus professor at the University of Adelaide who has been studying the evolution of the Sahara for more than 50 years, explains how the vast dry expanse we know today—one he describes as “sand, dust, and wind; wind, dust, and sand”—was once able to support ecosystems populated by dinosaurs, forests of enormous trees and eventually humans. By pairing the history of the Sahara with the story of his own decades-long quest to understand it, Williams strikes a careful balance of detailed scientific explanations and personal observations, bringing the mysterious space, from its “present aridity and the overwhelming evidence of a recently wetter past,” to vivid life.