Soil and Civilization: Complex Linked Systems.

Civilizations from Babylon to Easter Island prospered as long as the soil remained productive or there was new land to plow, and declined when neither remained true.  Archaeological studies in Greece, South Pacific islands, Central America, and other regions implicate soil erosion in the decline of ancient societies.  Although the rise and fall of each civilization was complex, the state of their soil set the stage upon which economics, climate, and warfare influenced their fate.  In a broad sense, many civilizations followed a common story line in which farming fertile valley bottoms allowed populations to grow to the point where they came to rely on tilling hillslope soils, which led to rapid erosion from rainfall and runoff.  Time and again, societies grew and prospered as long as there was new land to plow or the soil remained productive.  Many fell apart when neither remained true, although a few developed agricultural practices that conserved or improved their soils.  In the coming century, we face the challenge of simultaneously intensifying agricultural systems to feed a growing population and safeguarding both soil fertility and the soil itself.  Although history provides ample basis for concern about the long-term prospects for soil conservation, data from recent studies indicate that conservation agriculture could reduce erosion to levels close to soil production rates, and organic farming methods can enhance soil fertility.  Hence, we need not necessarily repeat the experience of past societies.