Many people have heard of Earth's largest deserts: the Sahara in northern Africa, the Gobi in east central Asia, and the Arabian in the Arabian Peninsula. However, some people may not know that these deserts weren't always so big. Desertification is the process by which natural or human causes turn previously productive land into desert areas. This book explores the different causes of desertification and the ways even longtime desert lands can change. Fact boxes and sidebars provide readers with additional information relating to the main text.