Detail from the cover of When the Rivers Run Dry.
Apart from concerns over energy and oil resources, economists say a global shortage of water would curtail the world's ability to raise food -- perhaps by 2025. Fred Pearce is an environmental and development consultant at New Scientist. His new book is When the Rivers Run Dry.
In the book, subtitled "The Defining Crisis of the Twenty-First Century," Pearce surveys levels of water resources and efficiency in more than 30 countries, sketching a picture of the future of the world's rivers.
Rivers have long been humanity's main source of fresh water. And from the Colorado River -- the first big success for U.S. engineers in taming a powerful river -- to China's long-running Yangzte River dam project, Pearce measures the long-term effects of dams.
His subjects range from the water disputes that often result from localized management plans to the effects on communities that have developed a unique culture over hundreds of years of living along riverbanks.