Walmart, once a lowly five-and-dime store founded by Sam Walton, has become a global giant. Its annual revenues rival the GDPs of major nations, its employees could field entire armies, and its customers number in the hundreds of millions-a week. But the company's obsessive push for "everyday low prices" at any cost has also made it a target for unions, local businesses, urban planners, and, most of all, environmentalists. The company's formidable buying power determines the fate of fisheries, forests, agriculture, and industrial production the world over.But a startling environmental revolution has taken place at Walmart, ignited by an unlikely alliance between a river guide-turned-corporate consultant named Jib Ellison and former CEO Lee Scott. In all aspects of Walmart's business-from packaging to promotions, and store layouts to supply chains-solutions are being devised that, due to Walmart's size, not only save billions of dollars, but also thousands of trees and millions of gallons of fossil fuels. Pulitzer Prizewinning journalist Edward Humes charts the course of this revolution, depicting the incredible ways in which the world's biggest corporation is making enormous strides in sustainability-and how whole sectors of the economy, from dairy to fashion, have begun to embrace Walmart's example.