Loss of topsoil is not as apparent today as it was in the 1930s. But it is happening, nationally and globally. Some 75 billion tons of topsoil are lost worldwide yearly, according to a study conducted by David Pimentel, a leading authority on soil loss. Soil loss within the USA accounts for an estimated 6.9 billion tons of the total. Meanwhile, to keep a diminishing amount of arable land productive, farmers have become increasingly dependent on chemical fertilizers.
U.S. farmers spend an estimated $20 billion a year to make up for the loss of nutrients carried off by erosion, putting multinationals such as Monsanto and Sygenta in the position of playing the role of physicians whose profits increase as the health of the planet declines. An agriculture based on the equivalent of chemical steroids is not sustainable.
Meanwhile, it is unsettling to realize that topsoil is not a renewable resource. As scientists at the University of California, Davis, have pointed out, "The rate of soil formation is very slow: it takes from 300 to 1,000 years for nature to replace the soil that a field can lose to erosion in 25 years at a loss rate of 1 mm per year."
In 1935, the state of Missouri, to cite only one example, lost 12 of its original 16 inches of topsoil. As David R. Montgomery points out in Dirt: The Erosion of Civilizations, "In the aftermath of the Dust Bowl ... the federal government began to see soil conservation as an issue of national survival." It remains an issue of national survival, for what is at stake is the future of our food supply, of farms and of farm communities, a way of life. It is a global concern, as well, for as Montgomery writes, "Earth's thin soil mantel is essential to the health of life on this planet, yet we are gradually stripping it off."