The hot and temperate deserts and their marginal steppe lands comprise one-third of the land surface of the world and are an increasingly critical area for the economic wellbeing of world populations. The remarkable mechanisms of floral, faunal, and human adaptation to the distinct and difficult environment of these arid zones, as well as the potential of modern technology for facilitating adaptation, are described and explained by Walton in the light of our most recent knowledge of the phenomena and processes involved.