When the Sahara Was Green: How Our Greatest Desert Came To Be
By Martin Williams
Princeton University Press, 2021

As Martin Williams points out in his fascinating new book, When the Sahara Was Green, the popular view most people have of the great Sahara desert is badly inadequate. Only about one-fifth of the Sahara consists of the endless procession of dunes and stretches of open sand; the rest ranges from mountains to rocky plateaux to barren gravel plains, and the one often shifts with melodramatic speed into the other.

Likewise most people would underestimate its sheer size - as Williams writes, it’s four times as big as the entire Mediterranean, an entire varied and savage world of its own. 

Williams is a professor of earth sciences at the University of Adelaide, and he first started visiting that wild world in the 1960s, studying the ground and the nature and the paleontological history and the life-forms that inhabit these different terrains today and in the past. And the main point of all this is indicated in the book’s title: the Sahara wasn’t always a desert. For almost 200 million years, dinosaurs roamed the area when it was characterized by rivers, lakes, swamps, wetlands, and lots of edible growth everywhere. Even millions of years after that, large swaths of the area got far more annual moisture than they do now - they were home to turtles, crocodiles, and hippos. 

And hominins: it was in Ethiopia, after all, that one of the most famous hominin examples of all, Lucy (Australopithecus afarensis), was found. “When the Ardipithecus and Australopithecus hominins were alive,” Williams writes, “the area in which they were living was a land of perennial lakes, rivers, and wetlands, with a variety of habitats ranging from riparian forest to savanna woodland and savanna grassland.” 

Anyone who’s ever spent time in the Sahara will find these things - dinosaurs, hippos, humans - almost impossible to imagine in the current setting, as blasted and inhospitable a place as any on Earth. And as engrossing a job as Williams does at bringing that older, greener, wetter Sahara to life, his readers are all going to be wondering the same question: what happened? What turned that verdant paradise into the harsh landscape it is today?

Williams is the best possible teacher for such questions. When the Sahara Was Green covers the cyclical, gradual desiccation of the Sahara, the changing of its biomes, the nature of its current occupants, and even the question of its future. It’s formidably researched - nearly 30 pages of fine-print End Notes close out the book - but so warmly, approachably written that learning was never so pleasant. It’s always a good sign - although staggeringly rare - to reach the end of a geological study and sincerely wish it were twice as long, but thanks to the narrative tone Williams takes throughout, firm but encouraging, discerning but open to wonder, this is one of those times.

Steve Donoghue is a founding editor of Open Letters Monthly. His book criticism has appeared in The Boston Globe, The Wall Street Journal, The Washington Post, and The American Conservative. He writes regularly for The National, The Vineyard Gazette, and The Christian Science Monitor. His website is http://www.stevedonoghue.com.