Unintended Consequences of Humans' Enormous Ability to Move Earth

Humans are now arguably the premier geomorphic agent shaping the surface of the earth. Humans first started moving significant quantities of earth to reshape their environment when they leveled floors of caves. Substantial increases in human earth moving occurred when the nomadic way of life of hunter-gatherers was replaced by agrarian life in settlements with attendant construction of shelters, and then later roads and public buildings. Major advances in both our motivation and ability to move earth then occurred in the Bronze Age, the Iron Age, and most recently during the Industrial Revolution.

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.