Hiding behind averages — soil erosion problems in Iowa

The EWG report illustrates the problems with averages. In some parts of the state a single 2007 storm led to over 100 tons per acre of topsoil eroding into rivers and streams in some parts of the state.

Will Hoyer
Will Hoyer

This week the Environmental Working Group released a report that shows that the rate of soil erosion in parts of Iowa is way worse than most people could have imagined.

Using data from the Iowa Daily Erosion Project, headed by agronomist Rick Cruse at Iowa State University, EWG’s report shows that Iowa’s statewide erosion rate of 5.2 tons per acre* can be very misleading and hides the fact that in some parts of the state a single 2007 storm led to over 100 tons per acre of topsoil eroding into rivers and streams in some parts of the state.

This illustrates the problem with averages. Sure, large parts of the state (the flatter parts of north-central Iowa, especially) might not be losing much soil at all, but other, hillier parts of the state are not doing so well.

And in some years, erosion might not be much of a problem because the storms just are not very severe, but as a report from earlier this year points out, climate change is driving more frequent and severe storms in Iowa — the kind that lead to catastrophic erosion.

Many current policies and practices are not helping the situation. When we speak in statewide averages we might think that those policies and practices are working better than they actually are.

Be sure to watch the 5 minute video that goes along with the report.

*In Iowa the “tolerable” soil loss amount, or “T,” is five tons per acre per year. This T value has been around for years and was theorized to be the rate at which soil was regenerated. Many experts question the validity of a T value of five and think that a truly sustainable soil loss limit would be significantly smaller

Posted by Will Hoyer, Research Associate