One of the oldest forms of earth moving is that involved in plowing. Plowing now displaces more soil than all of our other earth moving activities combined, and is creating the potential for a disaster of monumental proportions. Plowing on level terrain simply shifts earth back and forth. However, plowing on slopes results in systematic downslope movement of soil. In addition, plowing breaks up the vegetation mat protecting the soil, resulting in increased downslope movement by rain drop impact and erosion by runoff. Much of this soil ends up in colluvial deposits on slopes and on floodplains further downstream. The rest is deposited in the ocean. The former, and probably also the latter, result in distinctive stratigraphic horizons. More importantly, the loss of soil from agricultural fields now exceeds the rate of soil formation by weathering by about an order of magnitude. Long term depletion of the soil is occurring. The ability of Earth to support the human population is at stake.
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