THE GREEN SAHARA

Watering the desert.

Plants make rain, writes ecologist Gaudet, author of The Pharaoh’s Treasure: The Origin of Paper and the Rise of Western Civilization (2018). Forty percent or more of precipitation over land originates through evaporation from plants and trees. When vegetation is cleared, evaporation plummets, seasons come later, temperatures rise, and rainfall diminishes. Ten thousand years ago, the Sahara bloomed because the end of the last ice age—combined with changes in Earth’s axis—warmed the planet and increased rainfall. As the axis cycle continued, temperatures continued to increase, rainfall diminished, and by 3,000 years ago, the Sahara had dried up. Greenhouse gases filling the atmosphere over the past century have interrupted the cycle, which would ultimately have restored the Sahara, but the accompanying disordered weather increased rainfall in northern Africa, persuading some experts, Gaudet included, that reviving the Sahara is worth a try. The author embraces green technology and massive, climate-altering projects, arguing that these will jump-start the return of tolerable weather worldwide. Desalinizing has grown cheap enough to beget extensive, desalinization plants in every Saharan nation for drinking water and irrigation. Egypt’s Qattara Depression has long fascinated engineers who propose a pipeline from the Mediterranean to create a huge inland sea to cool the desert and support a large population. Once huge, Lake Chad is almost dry, but a canal from the Congo River basin carrying water over a thousand miles could revive it. Money and politics are the only barriers. Gaudet mildly approves an ongoing mega-project—the Great Green Wall, aiming to plant billions of trees across North Africa—but has more faith in a spreading practice among locals who have adopted farmer-managed natural regeneration that does not clear trees for crops but preserves and fosters them, enriching the soil. His surprisingly nonapocalyptic conclusion adds that carbon dioxide nourishes plants, and rising levels from global warming already produce significant greening of vegetation over much of the planet.

A compelling case for making the world’s largest desert lush.