Excessive tillage is leading to the erosion of topsoil, which is rich in nutrients, and in which the world grows 95% of its food. Scientists believe that if we continue to degrade the soil at the rate we are now, the world could run out of topsoil in about 60 years. Without topsoil, the earth’s ability to filter water, absorb carbon, and feed people plunges. One summer’s day in 2010, I was out walking in the countryside south of Toulouse in France, when I saw a tractor appear over the horizon and watched the farmer go to work.