Traditional farming retains soil structure, but intensive modern agriculture does not: Since the 1970s, while global grain production has tripled, an estimated 30 percent of the world's farmland has become too damaged to use. Also shrinking are the fossil fuel reserves for a system that requires petroleum to run the farm machines, serve as the chemical base of fertilizers, fuel the milling and processing plants and drive the food to widely dispersed consumers. Shiva puts it this way: "The new modified crops brought to us by the Green Revolution were described as 'green oil of the future.' Ironically, that has turned out to be correct in a way, as the Green Revolution makes a renewable resource -- food -- into a nonrenewable one, just like petroleum."