While I was in Iowa recently, Chris Jones, an environmental scientist at the Iowa Soybean Association, showed me this fascinating graph (based on this study). It basically shows how much dirt was in one of the main rivers flowing through Iowa’s farmland over the last century:

And then there’s the weather. A huge part of the erosion and water pollution that occurs each year can be traced back to one or two big storms — gully washers that rut fields. And we are seeing more of these big weather events, as abnormal becomes the new normal. “We claim improvement in a dry year, and then the sky is falling in a wet year,” said Keith Schilling at the Iowa Geological and Water Survey, who co-wrote the Raccoon River study that got my attention.

So, while we should give credit and encouragement where it’s due, in sum we’re still polluting with our food system.

What’s the solution? In a word, plants: Plants sheltering the earth during the big storms; plants slowing raindrops with their leaves; plants holding down the earth with their roots. In places, people have begun to restore critical sections of the old prairie. There was once 167 million acres of tall-grass prairie in the land where we now grow corn and soybeans, and less than .1 percent of that prairie remains.

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When I asked Eugene Turner, a professor at Louisiana State University, about this, he sent me the Marsden Farm study, which offers a potential way to mimic the prairie while still turning a profit. Researchers mixed things up by adding some grasses into the usual rotation of corn and soy.

Successful demonstration projects like this are sometimes hard to scale — it’s a lot easier to get results when you have a team of researchers scrutinizing the fields than if you are just one farmer trying to figure it out as you go along. And in recent years farmers have been pushed by a strong market incentive to just plant as much corn as possible. But as corn prices come down, perhaps more farms will look for alternative methods.