"Here's the key issue. Wal-Mart's carbon estimate omits a massive source of CO2 that is inherent to its operations and amounts to more than all of its other greenhouse-gas emissions combined: the CO2 produced by customers driving to its stores."
"The dramatic growth of big-box retailers, including Wal-Mart, Target, and Home Depot, over the last 15 years has been mirrored by an equally dramatic rise in how many miles we travel running errands. Between 1990 and 2001 (the most recent year for which the U.S. Department of Transportation has data), the number of miles that the average American household drove each year for shopping grew by more than 40 percent."
"Shopping-related driving has been growing so fast that even a phenomenal improvement in the fuel economy of cars would soon be eclipsed by more miles on the road. Nor is CO2 the only environmental impact of all of this driving. Tens of thousands of acres of habitat have been paved for big-box parking lots, which, during rainstorms, deliver large doses of oil and other petrochemicals deposited by cars to nearby lakes and streams."