FOOLING OURSELVES

The superficially reassuring national, regional or statewide averages of soil erosion obscure the real damage that is occurring on America’s agricultural land. Averaging soil erosion over states, regions or the nation obscures more than it reveals because erosion and polluted runoff do not occur “on average.” They occur when it rains. How much rain falls, how fast it falls, how wet the soil was before it started raining, how steeply the field slopes, how prone the field is to gullies, how much the soil is covered by a growing crop or crop residue, and how well the field and adjacent streams are protected by conservation practices ¾ all these factors determine how much damage is done by any one storm.

IDEP’s estimates of soil erosion occurring after each storm clearly demonstrate the danger of looking to statewide, regional or national annual averages of soil loss or runoff. There is every reason to expect that applying the Iowa project’s methods to other states would reveal the same disturbing picture.

These new data produce a far more detailed picture of the toll that erosion takes on soil and water and make it clear that farmers and policy makers must do much more to protect agricultural land from this old enemy.