The opening chapters of this book examine something that never occurred but was widely believed to have existed—the late 20th century desertification crisis in the Sahel. Recent advances in climatology and changing weather patterns have effectively terminated further scientific debate about the existence of widespread Sahelian desertification, providing us with an opportunity to take stock and draw lessons. The logical and empirical shortcomings of the concept of desertification have been known for decades but the idea has been institutionalized at the global level and is remarkably resilient. The middle section of this book presents new reasons for concluding that the concept of desertification is no longer analytically useful and that we should instead struggle to better define and measure dryland degradation. The closing chapters of the book provide case studies from around the world that examine the use and relevance of the desertification concept. Despite an increasingly sophisticated understanding of dryland environments and societies, the uses now being made of the desertification concept in parts of Asia exhibit many of the shortcomings of earlier work done in Africa. It took scientists more than three decades to transform a perceived desertification crisis in the Sahel into a non-event. This book is an effort to critically examine that experience and accelerate the learning process in other parts of the world.