What Will We Reap Without Topsoil?
You may have missed the research when it came out this February: a paper in the Proceedings of the National Academies of Science reporting on satellite studies of farmland topsoil in the nation’s corn belt, states like Iowa, Indiana, and Illinois. And the news was not good. The team estimated that more than one-third of the topsoil in this region is gone, eroded mostly from hilltops and ridgelines, thanks to the plowing and tilling processes used to perform industrial agriculture. That topsoil, some of the richest in the world, is carbon-rich and crucial to our food supply. And yet it’s continuing to wash away, a hundred years after scientists like Aldo Leopold first called out the threat of erosion.
This erosion, as well as other degradation of soil’s complex structure and microbiome, continues at a fast clip around the globe, hurting food production and ecosystems health. In addition, soil could be helping us contain more than 100 billion additional tons of carbon dioxide from the atmosphere—if we let it. But the good news, according to University of Wisconsin soil scientist Jo Handelsman, is that the solutions like cover crops and no-till farming are simple, well-understood, and easy to implement—as long as we give farmers incentives to make the leap. She talks to Ira about her forthcoming book, A World Without Soil: The Past, Present, and Precarious Future of the Earth Beneath Our Feet.
Invest in quality science journalism by making a donation to Science Friday.
Jo Handelsman is a soil scientist, director of the Wisconsin Institute for Discovery, and author of A World Without Soil: The Past, Present and Precarious Future of the Earth Beneath Our Feet. She’s based in Madison, Wisconsin.
IRA FLATOW: This is Science Friday. I’m Ira Flatow. You may have missed the research when it came out this spring, a paper in the Proceedings of the National Academies of Science reporting on satellite studies of farmland topsoil in the nation’s corn belt. That’s states like Iowa and Indiana and Illinois.
More than one-third of the topsoil in this region, more than one-third is gone, eroded mostly from hilltops and ridge lines, thanks to plowing and tilling processes used to perform industrial agriculture. That topsoil, some of the richest in the world, is carbon rich and crucial to our food supply. And yet, it’s continuing to be washed away decades after scientists first called out the threat of erosion to our soils.
Joining me to talk more about this problem, both at home and around the world, is Dr. Jo Handelsman. She’s a soil scientist and director of the University of Wisconsin Madison’s Wisconsin Institute for Discovery. Her forthcoming book is A World Without Soil, The Past, Present and Precarious Future of the Earth Beneath Our Feet. It’ll be out in a couple of weeks. Welcome back, Jo. Always good to talk to you.
JO HANDELSMAN: Thanks, Ira. Great to be here.
IRA FLATOW: A World Without Soil is a grim-sounding title. Is it literally that bad, what we’re facing?
JO HANDELSMAN: Well, of course, it varies. And every field is different from every other field, every country is different from every other country. And it depends on the practices on a particular plot of land, what is planted there and how the soil is treated. So the variation is, of course, enormous. But for example, if you had 1,000 tons of soil on an acre, which is kind of a common standard used, if we were eroding at 100 tons per acre per year, that would give us 10 years. Now that’s very fast erosion.
The USDA says that across the United States, we’re at more like five tons per acre per year. And so that would give us, certainly, many more decades. But we know that those numbers from the USDA underestimate total erosion because they don’t even take into account gullies, which are really a big part of erosion, where you get these big pits in the land, and the soil just flows right off. The details are what make this so scary, like the data you cited from Iowa and the corn belt. There’s just enormous erosion in particular areas. And some of them, as the article you cited says, are already devoid of topsoil.
IRA FLATOW: Yeah, well, let’s talk a bit how we got here. How did we get to this point? I mean we’ve had agriculture for, what, 10,000 years. Give us a little bit of the history of the changes that pushed us to this edge.
JO HANDELSMAN: Well, for many centuries, there were many people who farmed in a very sustainable way. And that was partly because the plow had not yet been invented. And so they used sticks and other simple materials to turn over their soil. And it didn’t have the destructive effect on soil structure, so the architecture of soil, that the plow does. For the most part, societies that have depended upon agriculture for food who didn’t treat their soil well, we don’t hear from anymore.
But the people who have been farming for thousands of years in the same place, like the Maya or the Zuni Indians of the US Southwest or the Maori, those are people who knew how to farm, and they know today how to farm. And they have sustained their farms because of the practices they use.
In contrast, when we started very intensive agriculture in, for example, the United States over the last 150 to 200 years, we started intensively plowing, planting single species of plants, which, in general, were the very extractive kind that took a lot from the soil and didn’t put back carbon into the soil. And that reversed thousands of years of soil production in, particularly, the Midwest of the United States, where we have, as you said, these just amazing, deep, rich, fertile soils.
IRA FLATOW: You talk about how the invention of the plow, invented in one way by Thomas Jefferson, you bring that up in your book as an important part.
JO HANDELSMAN: I find him a fascinating character because he stood for human independence and the independence of nations. And yet he was a slaveholder his whole life. And how do those two fit together? He also was a scientist. He looked at data. He loved doing experiments on his own land. He was, of course, a great farmer. And yet, he sort of denied the impact of plowing on the land. And so, some of his letters show how he thought that there was really no damage to the land from plowing.
But occasionally, you notice in his letters that he’ll mention something like his son-in-law learned to plow along the side of hillsides, instead of up and down. And he thought that was a really brilliant solution because it reduced the erosion of soil. And then, of course, he invented a new kind of plow that turned the soil over that made all sorts of farming that wasn’t possible before possible. But that, of course, also degraded a lot of soil across the US.
IRA FLATOW: And the lost soil isn’t just about the food we eat, right, as we’ve discussed before on this show and as you write in your book. Soil is also a place where we store carbon, except we’re not doing that very well right now.
JO HANDELSMAN: No, we’re not, and that’s the really sad thing because we could be handling a good chunk of our carbon problems with soil. Instead, we’re using soil as a source of carbon more often than as a sink. And so, the soil already stores three times the amount of carbon that’s stored in the entire atmosphere and five times as much as in all the plant life on Earth. So it’s the biggest terrestrial bank we have of carbon. But interestingly, there’s a lot less carbon in the soil now because of our farming. And we’ve lost an estimated 133 billion tons of carbon from our soil in the last 10 to 15 years.
IRA FLATOW: Wow.
JO HANDELSMAN: Isn’t that appalling?
IRA FLATOW: Yeah, it is, but I don’t think people really understand, chemically speaking, how carbon works its way from the air into the soil as a storage process. Could you get into that a little bit?
JO HANDELSMAN: Well, it’s mediated through plants. And of course, that’s the process of photosynthesis, which takes carbon dioxide and turns it into plant matter, all sorts of sugars and other molecules in the plants. A lot of that carbon that is fixed through photosynthesis in plants ends up in the roots. And a good portion of the carbon that ends up in roots ends up around the roots in the soil. It can be as much of as a third of the fixed carbon can end up in the soil.
And plants aren’t wasteful. They’re not fixing carbon just to feed it out to the rest of the world for no reason. Clearly, the microbes that they’re feeding in the soil are critical to plant health. And so, plants have evolved this mechanism of supporting those microbes through carbon secretion.
IRA FLATOW: Because on our program, we talk a lot about the microbiome in our bodies, and I’m always pointing out whenever we talk about the soil, that there’s a huge microbiome going on in the soil that is disrupted by how we tilled it, correct?
JO HANDELSMAN: Yes, the soil microbiome is the most complex environment we know of on Earth. There are thousands of species living together in the soil. And every soil differs in terms of its microbiome from every other soil. So, yeah, there’s a magnificent microbiome in soil. And it’s changed by planting a plant, by digging up a plant, by tilling the soil.
And probably one of the biggest changes we’ve seen is when we came to this land– I’m talking about European-Americans came to this land and started farming it. We had these deep-rooted perennials that filled the Midwest. And that’s what created these magnificent soils. Some of these plants will have roots that are as deep as 14 feet into the soil.
IRA FLATOW: Like switchgrass, right?
JO HANDELSMAN: Exactly.
IRA FLATOW: Just amazing stuff to the root structure, yeah.
JO HANDELSMAN: And those were feeding the soil, all of those perennials. Then we switched to these crops that extract everything they need from the soil. And they don’t put carbon back in. So one statistic I learned when I was writing this book that just astounded me was that at the end of a season, a perennial, because it needs its energy for the next season, will deposit as much as 70%, 7-0 percent of its carbon in the soil. A corn plant at the end of the season will leave 1% of its carbon behind. And so, it’s not very hard to figure out how the carbon went down so quickly when we were no longer replenishing it, and we were taking so much out with the harvest of our crops.
IRA FLATOW: OK, Jo, now give me some good news. Give me some hopeful news that there is a fix, there’s some way we can get around this problem.
JO HANDELSMAN: Today, people are so depressed about climate change, and they feel so helpless to make a difference because it’s such an overwhelming problem with so many facets. But soil carbon is one that we can fix quickly and easily. We just need to build the right social structure to do that. So there are three practices that Indigenous people have used forever that successfully nurture and protect the soil.
And so one is not plowing or not plowing very much. The second is using cover crops so that when there’s no crop being grown on that soil, there’s still a plant there to replenish it and protect it from erosion. And the third is to intercrop, so use some of these deep-rooted perennials, for example, interspersed with corn plants or whatever the crop might be. With those three methods and, in addition, using things like terracing to protect the soil from just flowing downhill, societies have protected their soils across the world.
And we could be implementing those methods if we had, for example, in this country, the right economic system. But we have these perverse disincentives for farmers to do the right thing. So, for example, if a farmer takes 10% of their corn out of production and replaces it with deep-rooted perennials, a study in Iowa showed that this practice would cut erosion by 95% immediately.
IRA FLATOW: No kidding.
JO HANDELSMAN: Yeah, but the farmer gets 10% less crop insurance because they’ve put 10% less corn in the field. So is that perverse or what? But we have control over crop insurance. We could fix that.
IRA FLATOW: Are there any new innovations or techie solutions that could really make a difference here? Or do we just need to do these really simple things that you’re saying?
JO HANDELSMAN: There is so much we don’t understand about soil, but at the same time, the methods that practically work are known. And so, yes, there could be techie solutions. For example, breeding plants to put more carbon into their roots and then into the soil– that would be a very effective solution. And maybe that could be done through genetic engineering or maybe by classical breeding. Or it could be accomplished through the farm management, the practices.
Another area is figuring out how aggregates of soil form. We know that bacteria and fungi are very important for sticking soil particles together. And when they’re stuck together in clumps or clods of soil, they’re much less likely to erode. So if we had more soil architecture like these aggregates, that would protect soil. And if we knew a little bit more about what helps the soil aggregate, perhaps we could have a techie solution, adding bacteria or certain fungi or maybe some carbon substrate that would help them produce the glue that sticks soil together. So, yes, I think there are some potential techie solutions, but the ones we have in hand right now are really critical.
I think the biggest techie answer that we need is how to control weeds in organic farming. And that may sound like a very, very specific thing. But it’s an enormous dilemma because in other kinds of farming, you can use herbicides to kill the weeds. In organic farming, the only way that they have is plowing. And so they’re stuck with this destructive practice because there’s no alternative allowed, or they become uncertified as organic farmers. So I think we owe the organic farmers some great solutions on managing their weeds.
IRA FLATOW: This is Science Friday from WNYC Studios, talking to Jo Handelsman about the threats to soils and how we can restore them. I’ve heard that some of the high tech solutions they’re thinking about are hydroponically growing plants indoors vertically, right? I’m sure you’ve seen this. Is this a solution, or is it just not big enough to feed the rest of the world?
JO HANDELSMAN: We sort of explored that when I was in the White House. And all of the evidence and the calculations that I could find showed that for vegetable crops and produce, probably that is part of the solution, is to do vertical farming and hydroponics. But for our staple crops, like rice and wheat and potatoes and corn, there’s no way that those could be grown hydroponically or in any method that people can even imagine today that would produce enough to feed what we expect to be the 10 billion people by 2050. It just, it can’t happen.
IRA FLATOW: I have to say I know this has been a problem for decades that we have the dead zone in the Gulf that you talk about, the need for no-till agriculture. I know you’ve been studying it, what, for years. Why haven’t we solved this yet?
JO HANDELSMAN: Well, that’s been one of the questions I’ve had. When I was in college, no-till agriculture had just been invented. And those were really heady times in agronomy. People were so excited about that. And they thought that no-till was going to be the answer, that if we stop plowing, we’ll stop destroying our soil. And there was an act in 1985, the Food Security Act, that encouraged and paid farmers to do the right thing and to manage their soil properly and not overtill it. And that started cutting soil erosion right down. It was just– it was dropping steadily.
And so I kind of lost track of erosion. I have to admit, once that started happening, I said, OK, we solved that. We’re done. But what I didn’t know until I started looking into this when I was at the White House was that in 1992 and then subsequent farm bills, the Farm Bill started eroding the money that USDA had for holding farmers accountable for these soil management plans. And very sadly, we started seeing erosion start increasing in some areas and leveling off in others. And we didn’t see that tremendous decrease in erosion rates continue.
And so the question is why, and I think it comes down to incentives for farmers farming. Farmers work on the edge. They are so close to not making a living that they can’t take risks. And we need to support them to take those risks and the financial risk of saving their soil.
IRA FLATOW: Well, I’m glad you’ve come on our show to talk about all those things because we really do need to hear them. And we need people like you who will tell us, Jo.
JO HANDELSMAN: Thank you so much, Ira. It was great to see you again.
IRA FLATOW: Dr. Jo Handelsman, soil scientist, author of the forthcoming book, A World Without Soil, The Past, Present and Precarious Future of the Earth Beneath Our Feet, a really good and timely read. And you can read an excerpt on our website, sciencefriday.com/soil.
Christie Taylor is a producer for Science Friday. Her day involves diligent research, too many phone calls for an introvert, and asking scientists if they have any audio of that narwhal heartbeat.
Ira Flatow is the host and executive producer of Science Friday. His green thumb has revived many an office plant at death’s door.