I found myself thinking about topsoil and the west so I went to the search engine. Nebraska Public Media has a piece from last April:

A few years ago, Isaac Larsen attended a wedding at a pioneer church in Minnesota. After the ceremony, he wandered around a cemetery by the church.

He noticed the cemetery, which had never been tilled, was at least a foot higher than a corn field just on the other side of a fence.

Tilling erodes soil.

The University of Massachusetts Amherst geosciences professor and his co-researchers have released a new study that found topsoil in the Midwest is eroding at an average rate of 1.9 millimeters per year. They measured elevation differences between native prairie and farm fields at about 20 sites, the majority in central Iowa, with some in Illinois, Minnesota, South Dakota, Kansas and Nebraska.

The researchers estimate the Midwest has lost 57.6 billion metric tons of topsoil since farmers began tilling 160 years ago. This erosion, Larsen said, makes it more difficult and more expensive to grow crops.

“We’re going to need to feed more people in the future,” he said, “and degraded soils that have lost their organic rich horizons just aren’t as productive.”

We might not need to feed more people in the future though. The consequences of the other ways we’ve eroded and degraded the world we live in are already thinning populations and it’s not looking as if we’re going to slow that down much.