Last week I received a package in the mail I had been waiting for since December – a book that University of Missouri professor of plant science, Dr. Peter Scharf recommended at last year's Crop Management Conference. The book, "Dirt: The Erosion of Civilizations," by David. R. Montgomery outlines the importance what many consider one of the world's most underrated natural resources.
Many have made the case of the need for reducing soil erosion, perhaps most notably Hugh Hammond Bennett, who made his famous address to President FDR on Black Sunday as the Dust Storms carried the Great Plains soils into Washington D.C. "This, gentlemen, is what I have been talking about." Over time, many have adopted conservation farming practices. So, it may seem like I'm preaching to choir.
However, it wasn't until recently that I learned of the even bigger scope of dirt's importance and impact on civilizations. Montgomery points out that it is too simplistic to blame the fall of civilizations like Rome on just soil erosion, but it definitely played a role.
From 4000 to 1000 BC agriculture in Italy spread from more fertile ground to steeper slopes and valleys. By 500 BC, iron was widely used in plows to carve through topsoil and into denser subsoil. "…all that plowing slowly pushed soil downhill and promoted erosion, as runoff from each storm took its toll – slow enough to ignore in one farmer's lifetime, but fast enough to add up over the centuries," Montgomery writes.
Decreasing yields in central Italy required expansion into new farmland. The countryside around Rome fed the city until late in the third century BC. By the time of Christ, grain from the surrounding land couldn't feed Rome. 200,000 tons of grain were shipped annually from Egypt and North Africa to feed Rome's population of a million people. Eventually, North Africa, conquered by Rome for its fertile land, declined from erosion as well, Montgomery writes.
"Soil erosion progressively degraded the Roman heartland and then spread to the provinces – except Egypt, which became a colony exploited to feed Rome upon the death of Cleopatra in 30 BC," Montgomery writes. "By the end of the empire, the dirt of the Nile fed Rome."