Oil, if you wait long enough, is a renewable resource. Take dirt. On the other hand, please don’t. Dirt, in theory, is renewable, too, if you are sufficiently patient. Moreover, it is just as strategic a resource as petroleum.
We all know about soil erosion. There is even a “peak dirt” movement. Awareness is high, but the record remains abysmal, and it does matter. The history of dirt suggests that the way people deal with their arable soil can dictate the lifespan of civilizations. “With just a couple of feet of soil standing between prosperity and desolation,” writes geologist David R. Montgomery in Dirt: The Erosion of Civilizations, “civilizations that plow through their soil vanish.” A civilization that treats its dirt like dirt, in other words, will ultimately fail.
How much soil are we losing? The world has three major regions containing truly Grade A topsoil: Northern Europe, Northern China, and the American Midwest. The dynamics of dirt making are the straightforward result of a balance between the forces of weathering, which produces new dirt, and the processes of erosion, which take it away. Most soil profiles are one to three feet in depth, and most of the world’s soil is only marginally fit for farming.
There is nothing new about losing soil. George Washington called the agriculture of his time “as unproductive to the practitioners as it is ruinous to the landholders,” according to Montgomery. Jefferson also took up the complaint. The problem for agricultural states was that it was always easier to colonize new fields than to laboriously manure and care for the old ones.
George Perkins Marsh, a prominent 19th Century proto-environmentalist, argued that Rome, among other empires, died for lack of dirt. “Territory larger than all Europe,” he wrote, “the abundance of which sustained in bygone centuries a population scarcely inferior to that of the whole Christian world at the present day, has been entirely withdrawn from human use…”
In the U.S., a report by the Commissioner of Patents in 1849 tried to quantify the picture: “One thousand millions of dollars, judiciously expended, will hardly restore the one hundred million acres of partially exhausted lands.”
Montgomery even makes the argument that soil erosion in Southern states may have helped set off the Civil War, since it virtually assured that slavery was required for profitable agriculture.
By 1928, the U.S. Department Agriculture estimated that the nation’s soil was eroding ten times faster than it was being formed. In 1934, windstorms across the Dakotas picked up more than 300 million tons of topsoil and hurled it eastward at a hundred miles and hour. In Chicago, four pounds of dust per citizen rained down on the city.
By the time of the American Bicentennial, a third of the nation’s topsoil was gone for good. At the same time, the federal government began cutting back on funding for agricultural conservation programs.
By the 1990s, writes Montgomery, “Indiana farms still lost a ton of soil to harvest a ton of grain.” The USDA estimates that roughly half of the fertilizer used each year by American farmers does nothing but replace soil nutrients lost to erosion. This puts us in the odd position, writes Montgomery, “of consuming fossil fuels—geologically one of the rarest and most useful resources ever discovered—to provide a substitute for dirt—the cheapest and most widely available agricultural input imaginable.”
If that isn’t nonsensical enough for you, try this: Over the last 500 million years, soil erosion rates have been estimated by geologists to be on the average of an inch every thousand years. Today’s rate is believed to be closer to an inch every 40 years—a rate of soil-stripping that is clearly unsustainable.
Since soil conservation never seems to be a hot-button issue, one answer may lie in urban farming—the adoption of small-scale farming to urban settings. The alternative—mass food shortages—is another method of ultimately focusing our attention on the care and feeding of the nation’s soil.