Agriculture and the Erosion of Civilizations.

Can an agricultural system capable of feeding a growing population safeguard over the long run both soil fertility and the soil itself? Addressing this fundamental challenge faces modern agriculture — and therefore global society —over the upcoming centuries. Data drawn from a global compilation of studies quantitatively confirm the long articulated contention that erosion rates from conventionally plowed agricultural fields greatly exceed rates of soil production, erosion under native vegetation, and long-term geological erosion. In particular, data compiled from around the world show that soil erosion under conventional agriculture exceeds both rates of soil production and geological erosion rates by up to several orders of magnitude. However, the general equivalence of the latter support the idea that hillslope soil production and erosion evolve to balance geologic and climate forcing, whereas conventional, plow-based agriculture increases erosion rates enough to prove unsustainable. Net soil erosion rates in conventionally plowed fields (ca. 1 mm/yr) can erode through a typical hillslope soil profile over time-scales comparable to the longevity of major civilizations. Although the experiences of past societies provide ample historical basis for concern about the long-term prospects for soil conservation, data compiled in recent studies indicate that no-till farming could reduce erosion to levels close to soil production rates. Consequently, agricultural production need not necessarily come at the expense of either soil fertility or the soil, even if recent proposals to rely on conventionally grown corn for biofuels exemplify how short-term social and economic trade-offs can de-prioritize soil conservation. Like the issues of climate change and loss of biodiversity, the ongoing global degradation and loss of soil presents a fundamental social challenge in which the slow pace of environmental change counter-intuitively makes solutions all the more difficult to adopt.