“Over the last few years, researchers from across the world have noticed that we’re using soil up faster than it’s regenerating — and the most dire predictions say that we could have fewer than 60 years left — that’s 60 harvests — before we run out of soil.”

What if you knew how the world was going to end? In this episode, we dive into the story of the Dust Bowl, which decimated 250,000 square miles of land in the United States in the 1930s, and Hugh Bennett, the man who saw it coming and tried to warn people—even when no one wanted to listen.

How do we use—and misuse—soil for our own ends? Are we missing the signs that another environmental catastrophe is on the way?

Presented by Dan Crane
Written by Ian Steadman & Eli Lee
Sound design by 
Laura Irving

Made with the support of The Bill & Melinda Gates Foundation

Featured guests

Music & audio credits

Show notes

Some additional information and resources not directly linked to within the transcript (below):

  • An assessment from 2014, a decade after the release of The Day After Tomorrow, of the film’s effects of on both the representation of climate change in cinema, and the resulting public (mis)understanding of the issue.
  • More context on that claim that we only have “60 harvests left” before we run out of soil.
  • The USDA has produced its own documentary about the work and legacy of Hugh Bennett:
  • You can also ready Bennett’s seminal study, “Soil Erosion: A National Menace,” here.
  • For a thorough social and geologic history of the Dust Bowl, from its origins 37 million years ago to after-effects still being felt today, check outentries from Jay Owens’ extremely good newsletter about dustOnetwothree.
  • Timothy Egan’s The Worst Hard Time is the definitive history of the Dust Bowl from the perspective of those who actually lived through it.
  • Details of the study that found Dust Bowl conditions in the modern U.S. would reduce crop yields by 30–40 percent. (That’s actually slightly worse than what happened in the 1930s.)
  • An English translation, from an American edition, of Baron Justus von Liebig’s lengthy treatise on maximizing nutrients in soil.


DAN CRANE: What if you knew how the world was going to end?

DENNIS QUAID: What we have found locked in these ice cores is evidence of a cataclysmic climate shift, which occured 10,000 years ago.

DAN CRANE: That’s Dennis Quaid, in the 2004 movie The Day After Tomorrow. It was a huge blockbuster hit, grossing more than $600 million worldwide, but just in case you haven’t seen it: it’s a climate change disaster movie, where most of the northern hemisphere gets covered by ice caps in a new flash-freeze ice age. Dennis, maybe you could explain.

DENNIS QUAID: Let me explain. The northern hemisphere owes its temperate climate to the North Atlantic current. Heat from the Sun arrives at the equator and is carried north by the ocean. But global warming is melting the polar ice caps and disrupting this flow. Eventually it will shut down. And when that occurs, there goes our warm climate. If we do not act soon it is our children, and our grandchildren, who will have to pay the price.

DAN CRANE: This is one of those tropes disaster movies always seem to use (and which is easy to parody) — the scientist, gravely presenting his findings to an audience of skeptical politicians.

KENNETH WALSH: And who’s going to pay the price for the Kyoto Accord, which will cost the world’s economy hundreds of billions of dollars?

DENNIS QUAID: With all due respect Mr Vice President, the cost of doing nothing could be even higher. Our climate is fragile. At the rate we’re burning fossil fuels and polluting the environment, the ice caps will soon disappear.

KENNETH WALSH: Professor, uh, Hall. Our economy is every bit as fragile as the environment. Perhaps you should keep that in mind before making sensationalist claims.

DAN CRANE: Sure — this is a Hollywood-style account of how scientists talk to politicians, in a movie where New York City is flooded by a tsunami and then frozen under ice during the largest storm in recorded history. In interviews, director Roland Emmerich remains staunchly unembarrassed by the scientific liberties he took — and it’s not an accident that Kenneth Walsh, who plays the Vice President character in the clip you just heard, looks and sounds like former US vice president Dick Cheney. Emmerich wanted to make a political point about our impact on the environment. Accuracy isn’t critical here. Attention-grabbing is, no matter how confusing or misleading the movie might have been about what climate change is to the average viewer.

Welcome back to The Thin Layer, a podcast about dirt, with me, Dan Crane. Today’s episode is all about whether we’re all going to die because we’re running out of soil.

Yeah, I know. “Running out of soil” sounds… absurd, when there’s probably soil outside your nearest window, even if you’re in the middle of a city. I can go on Amazon right now and next-day ship literally tonnes of soil to my house, if I wanted to. And it would get there the next day. Thanks, Amazon Prime. But consider this. An increasing number of soil scientists think that we could well be heading towards a future without soil, unless we change course. Over the last few years, researchers from across the world have noticed that we’re using soil up faster than it’s regenerating — and the most dire predictions say that we could have fewer than 60 years left — that’s 60 harvests — before we run out of soil.

Think of it like this. When we farm, we’re transferring the nutrients and energy in the ground, into plants or animals, and then we truck those plants or animals away to eat. How does new energy, in the form of new nutrients, get back into the soil for the next harvest? The answer to that question — and how reassuring that answer is — depends on who you ask.

But first we’re going to tell you about the Dust Bowl, which, well, I learned about it in high school, and I’m sure a lot of you did as well. But I never learned about the guy who knew it was coming, decades in advance — or the Day After Tomorrow-style theatrics he used to get people to take his warnings seriously.

Born in 1881 in North Carolina, Hugh Bennett was a farmer’s son. He trained to be a chemist, but his first job straight out of college was for the US Department of Agriculture, studying soil. Across the US, farmers were getting less and less food each year from their harvests. The USDA sent workers like Bennett out to try and find out why.

In 1905, he found himself in Virginia — on a farm, with dirt hard and dead like clay. Next to it, a forest, with healthy, brown, crumbly soil. It hit him like lightning: the way farmers treated the land was killing it. And you can guess what happened next: no one except Hugh Bennett cared. The U.S population was booming, and the federal government was desperate to increase food production — and many farmers needed to grow as much food as possible to scrape a living. Everyone’s incentive was to try and pump as much food out of the ground as possible, not care about the environment. So he tried to make people care. Over the next two decades as he travelled the US studying the soil, he gave town hall talks and lectures, and wrote for pop-science magazines as well as scholarly journals — trying to build up awareness of soil erosion as a when, not if, problem.

By 1928 Hugh finally seemed to be getting the attention he wanted, after he wrote an influential paper called “Soil Erosion: A National Menace” — now, it might not sound like much, but in the world of environmental science it was a blockbuster hit. He laid out in painstaking detail how the way U.S. farmers grew crops made it easy for millions of tons of soil to be washed into rivers or blown away by the wind every year. Eventually, he said, a tipping point would be reached — millions of acres of US farmland would have to be abandoned. And then, just when the USDA finally gave Bennett the chance to set up a bunch of sites to study soil erosion, the stock market crashed, the Great Depression began, and farmers were forced to squeeze even more food out of their land, speeding erosion up even faster.

Then, in 1933, two things happened. One, the worst drought to hit the United States for 300 years was underway on the Great Plains, causing larger and larger dust storms. Two, the federal government wanted to spend its way out of the Great Depression, and that included the founding of a temporary national Soil Erosion Service. Hugh — the farmer’s son who’d spent half his life campaigning to be taken seriously — was put in charge.

NEWSREEL ANNOUNCER: Listen to the warning of Hugh Bennett, director of United States Soil Erosion Service

HUGH BENNETT: We Americans have been the greatest destroyers of land of any race or people, barbaric or civilized. Unless immediate steps are taken to restore grass to millions of acres to these sun-scorched, wind-eroded lands, we shall have on our hands a new manmade Sahara, where formerly was rich grazing land.

DAN CRANE: In 1935, Bennett had the chance to argue before Congress that the Soil Erosion Service needed to be made a permanent agency. Luckily for Bennett — if luck’s the right word for it — a large dust storm kicked up a few days earlier out in Kansas, moving towards the east coast, towards Washington, D.C.

HUGH BENNETT: Its arrival, I thought, might settle any senatorial misgivings.

DAN CRANE: He stretched his testimony out as long as possible, reaming off data and going into minute detail, trying to stall for time — until finally, late in the day, he got his theatrics.

HUGH BENNETT: A modern miracle. One of the senators remarked it’s getting dark. Another senator mentioned maybe it’s dust. I said you’re right senator, it’s another dust storm. We went back to that table, and I was feeling pretty good.

DAN CRANE: Other reports — which might be exaggerating for effect, I should point out, but in the spirit of sensationalism I’ll repeat anyway — have it that Bennett gestured to the windows as they darkened and intoned: “This, gentlemen, is exactly what I am talking about.”

Not long after, another enormous dark and dusty storm rattled across the Midwest. It was on that day in April became known as Black Sunday, when the storm hit an area centered on the Oklahoma panhandle, that Associated Press editor Edward Stanley first described as “the dust bowl”. The years of the Dust Bowl saw the topsoil of over more than 250,000 square miles of land just… blow away. For context, that’s about the size of France, nearly 1/20th of the total land on Earth used for growing crops.

Half a million Americans were left homeless after their farms were destroyed — suffocated beneath a blanket of dust — adding another layer of despair during the worst times of the Great Depression. Many modern American families, particularly out in California, are descended from the hundreds of thousands of “Okies” who kept moving west, trying to escape poverty and dust. Congress had no choice but to fund the permanent Soil Conservation Service. Hugh Bennett was its first director, and he is now remembered by the USDA as “the father of soil conservation.”

Hugh Bennett’s approach to fixing the land was pretty simple — get government scientists to walk through the fields with farmers, listen to their problems, study the exact conditions on a farm, and design a scientific solution that worked for that specific part of the country. He won over the respect of the farmers — and, as a farmer’s son, he came across as a peer, not a meddling bureaucrat. But it took thinking like a Hollywood director to get the powers that be to take action. And we know this because Bennett wasn’t actually the first person to predict that the Great Plains were going to be farmed to death. Just get a time machine and ask any late-19th century cowboy what he thought about plowing up parts of Oklahoma or Nebraska or Wyoming. He’d probably quote an old of saying of theirs about the Great Plains: “Miles to water, miles to wood, and only six inches to hell.” That’s my, that’s my great Walter Brennan impersonation.

The Great Plains today may look like prime farmland, but once upon a time this part of the world was known as The Great American Desert. There was a lot of life in the Great Plains, of course — and there were plenty of people already living on them — but from the perspective of the early American republic in the 18th and 19th centuries, looking west, the flat, treeless, featureless grasslands didn’t look like potential farmland. It looked like land for livestock grazing at best. The soil was too thin and delicate to handle being plowed — the incessant wind would dry it up and whip it all away. Except, by chance, the late 19th century was unusually damp on the Great Plains. It made them seem greener, more hospitable, than they had before. The U.S. government, hungry to expand and with a growing, hungry population to feed, paid people to turn the plains into farms, and collective memory of the “Great American Desert” faded. But when the droughts came back in the 20th century and the thin topsoil began to blow away, those people who’d had the sense to warn against farming the Plains were proved correct — whether because of damaging farming practices, like Hugh Bennett, or the simple fact that the land itself resisted plowing, like the cowboys. You’ve got to work with nature, not against it.

FRED KIRSCHENMANN: Well, as I’m sure you know, we have basically not paid attention to soil health for, you know, almost a hundred years now.

DAN CRANE: Fred Kirschenmann is director of the Leopold Center for Sustainable Agriculture at Iowa State University. His parents bought a farm in North Dakota in 1930, and just about stuck it out during the Dust Bowl years — he’s inherited his father’s reverence for soil conservation.

FRED KIRSCHENMANN: So he became a big advocate of the importance of taking care of land. I can still see him in my mind’s eye, when I was about five years old, him lecturing me with his finger stuck out at me, about how important it was to take care of land, that was more important than anything else.

DAN CRANE: Soil conservation is a reasonably mainstream concept these days — but in many ways, a lot hasn’t changed, and especially our attitude towards soil. To understand exactly how, we need to go back in time a little bit.

FRED KIRSCHENMANN: We evolved as humans on the planet roughly 200,000 years ago, and for the first 190,000 years we fed ourselves as hunter-gatherers. We were not food producers, we were food collectors. And then, in about ten to twelve thousand years ago, we started to transition to produce food, and we started to do agriculture.

DAN CRANE: We became farmers.

FRED KIRSCHENMANN: And most of that was a kind of slash and burn agriculture.

DAN CRANE: That means cutting down all the plants and trees on a patch of land, literally burning it, then using the ash from the fires as fertilizer for crops — one of the earliest examples of the kinds of ash cycles we talked about in episode one. There’s a kind of natural cycle that emerges from this — you’ll get ten, maybe 15 years of crops before needing to move, and needing to leave the old land alone to regrow for another 15 years. Nature applied an inescapable speed limit. You could top fields up with manure, sure, but the amount of food you’d get from any patch of land stayed pretty much the same from the time of Ancient Babylon through to the Industrial Revolution. And then… we discovered how to make food from thin air.

In 1840, the German chemist Baron Justus von Liebig, a pioneer of modern agricultural science, published the secret to huge crop yields. I’m going to save you reading all the 400-plus pages of the book that he wrote about it, plus it’s in German, and just tell you that it comes down to this: the crops you get from a harvest depend on what he called the “quantity of food” in the soil. So, that’s things like nitrogen, phosphorus, potassium — plant food. From that, subtract any “resisting forces” — stuff like pests, for example, or toxicity. Think of it like soil’s an engine, and your nutrients are your fuel.

FRED KIRSCHENMANN: The minimum input for the maximum output, and so that really started down this path of, and primarily just using basically nitrogen, phosphorus, and potash, and then we didn’t have to worry about the laborious process of, you know, taking care of the soil.

DAN CRANE: The bottleneck was nitrogen, until the early 1910s, when German chemists Fritz Haber and Carl Bosch tried to figure out how to make bombs for the German army and accidentally discovered how to make fertilizer. It changed everything. Without nitrogen fertilizers, the world’s population would be a quarter of the size it is now. More than half of the nitrogen in your body — without which you wouldn’t exist — was at some point pulled out of the air in a lab or a factory somewhere so it could be fed to plants, and, via the food chain, you.

And the U.S. in particular is a big fan of nitrogen fertilizer — although the U.S. has just five percent of the world’s population, it consumes around 12 percent of global nitrogen fertilizer production. But the downside here is kind of the same downside that the cowboys foresaw in the Great American Desert; the same downside that Hugh Bennett spotted 30 years before the Dust Bowl became a catastrophe. You treat soil like dirt, you end up with… dirt.

RONALD AMUNDSON: In areas that started farming thousands of years ago, and now look at the quality of the landscape. I think soil erosion, the loss of soil by wind and water, has been one of the most devastating impacts to agricultural production over the centuries, and it’s an ongoing issue today and around the world.

DAN CRANE: This is Ronald Amundson, chair of the Department of Environmental Science, Policy, and Management at UC Berkeley. As he says — look around the world today, and there’s soil loss everywhere. On its own it’s not the worst thing in the world, and some degree of erosion is always unavoidable. The last century has been different.

RONALD AMUNDSON: Our fertilizer and nutrient management system right now is typical of much of the economy, or the ways in which goods and services are produced and consumed, it’s kind of a linear economy.

DAN CRANE: Raw material gets turned into a product, the product gets consumed, and the waste gets dumped somewhere. It’s that mindset that dirt is just an engine, and nitrogen and other nutrients are fuel, and it’s no more complicated than that. The land can break in other ways — your fertilizer’s no good if it’s blowing away, or washing into water and poisoning fish. And while conservation programs mean there’s half as much soil erosion on US farms as there was in the 1980s, for example, it’s still happening way too fast for soil to regenerate itself.

I said at the start of the episode that we might only have 60 harvests left until the end of the world. Many scientists, and the UN, have reiterated this over the last few years, and their warnings aren’t necessarily over-dramatic — the problems are potentially dire. Soil might not be an engine, but it is like a non-renewable energy source, in that it’s really easy to use up, and very hard to replace.

ELIZABETH BACH: You know, an inch of soil takes over a hundred years to form, but in terms of losing things like the nutrients in the organic matter that those soils accumulate over very long periods of time, that can happen surprisingly quick.

DAN CRANE: This is Elizabeth Bach, the executive director of the Global Soil Biodiversity Initiative, based at Colorado State University. We met her in our previous episode, where we talked about wildfires and climate change. Her family also had a farm, in Missouri, that had to be abandoned during the Dust Bowl. When you talk to American soil scientists, maybe unsurprisingly, a lot of them have a personal connection to the Dust Bowl.

Her research actually focuses on the problem of how to handle places like the Great Plains, large expanses of grassland, where they’ve been degraded by farming.

ELIZABETH BACH: So if you think about a grassland soil like from the central US or Ukraine or one of those areas, the act of plowing and farming that soil can result in the loss of about a third to half of it. Most of that happens in the first kind of five to ten years of usage in the soil. It goes pretty quickly.

DAN CRANE: Intensively farming the land doesn’t just make soil erosion possible — that’s when you’ve got wind or water physically taking the soil away. You also get soil degradation — the soil quality itself declines. In part, because soil’s full of microbes that breath in oxygen, eat carbon in the soil, and then exhale carbon dioxide. Every time you plow a farm, for those microbes, it’s like opening a window for fresh air — and they go to town. If you stop and let the land settle, it can take anywhere from 20 to 400 years for the land to recover.Erosion and degradation together have reduced how much land we have available to grow on around the world since we started farming 10,000 years ago, and it’s kicked up a notch in recent human history. Fred Kirschenmann again.

FRED KIRSCHENMANN: Iowa has some of the richest and deepest topsoil in the world, but it has now, since we started to do agriculture here in the late 1800s, Iowa has now on lost six inches, on average, of topsoil.

DAN CRANE: So, when the UN warns us that we only have 60 harvests left until we “run out of soil”, this is precisely the kind of thing they’re talking about. As much as humans have been farming for thousands of years, the way we’ve been farming over the last century or so is way more intensive. In doubling down on soil as something we can pump food out of, we’ve doubled down on a way of farming that sucks the life out of the land and makes it far more prone to erosion and degradation.

And it’s worth bearing in mind that 60 years is an average — different factors in different parts of the world are going to, well, make a difference. In North America, the main reason for soil degradation is, as you might have guessed by now, large-scale industrial agriculture. In South America, deforestation is the main reason, and in Africa, it’s desertification. These are broad brushstroke reasons, and the story is a lot more complex when you get down the local level, but the story remains the same — about 40 percent of the world’s soil is already degraded or seriously degraded.

The popular story is that Hugh Bennett’s work and legacy means that at least we won’t have another Dust Bowl. But that’s not strictly true. Soil conservation is a big part of it, but this is still the Great American Desert we’re talking about. If it can’t be grassland, then, well, it wants to be dust. Maybe another Dust Bowl will happen when the Ogallala aquifer running from Texas to South Dakota — where 30 percent of all water used to irrigate US farms comes from — runs out in 25 years. Maybe it’ll be when another 1930s-level drought hits — studies have shown that such a drought would reduce wheat and corn harvests by as much as 40 percent. Maybe it’ll just be the general upward tick of temperatures due to climate change, and the fact that the soil exposed in the northern parts of the world — which we talked about in our last episode — won’t be ready to be grown on fast enough to replace the other soils nearer the equator that are reduced to desert. The world’s population is still rising, and every year we need to feed more people with less land.

ELIZABETH BACH: Just a few weeks ago, I was driving through Wyoming, not far from where I live in Colorado and there was this giant wall of dust blowing across the road and I was like, whoa, these are like what those old photos looked like, so there’s places where we actually do see a lot of dust movement and erosion, even today.

DAN CRANE: But enough despair, my god! Can we get some hope in here? Please?

FRED KIRSCHENMANN: My student came into my office one day with a photograph of two hands of soil.

DAN CRANE: Alright, here we go. Lay it on me, Fred.

FRED KIRSCHENMANN: One which was soil that came from land that his father farmed, who, he didn’t officially farm organically but he did in terms of how he farmed and the way he took care of land. So he showed me this photograph of that hand of soil, and then alongside that, another hand of soil that came from a neighbor, who farmed in a more conventional way, and it was like two different planets. I mean, the soil that came from his father’s land was dark and porous and earthworms hanging off the edge of his hand, and the soil from the land from his neighbor was like a handful of sand. So then in my mind I start to see my father’s finger about, you know, how important it was to take care of land.

DAN CRANE: This is how “organic farming” spread among farmers in the latter stages of the 20th century — people noticed that their land wasn’t doing great, looking at what their neighbors were doing differently, and adjusting.

When Hugh Bennett came up with ideas for halting and reversing the Dust Bowl, he did the same thing — travelling the country, listening to people, studying soil, and experimenting with what worked best. He came up with a list of suggestions: no more deep plowing, for one, as well as using techniques like “terrace” and “strip” farming, where land is shaped to limit wind exposure — techniques which are almost as old as agriculture itself in other parts of the world. He also suggested cover crops, plants which grow on the land between harvests, holding the soil together with its roots.

Organic farmers don’t use artificial chemical fertilizers — they use manure and mulch. Pesticide use is severely restricted. They use crop rotation in a way that develops healthy, living soil, full of microbes, and there’s no allowance whatsoever for genetically-modified plants or animals.

Organic farming is one of the biggest, most well-known sustainable approaches to farming, but isn’t the only way — just as there isn’t any one definition of “conventional agriculture.” Plenty of farmers pick and choose from a range of sustainable techniques. For example, there’s this concept of “low-till” or “zero-till” farming, where you try to disturb the ground as little as possible. When old crops are harvested, you leave all the old leaves and roots and stems to rot and turn into mulch, so you’ve got a nice carpet of dead stuff to shelter the ground from the wind — and you don’t plow the ground up before planting seeds either. The downside is it can cause a problem with weeds, and if you’re an organic farmer, you can’t use weed killer. So what to do?

FLAMETHROWER TRACTOR CLIP: OK we’re watching John take off, he’s gonna hit the burners pretty soon.

DAN CRANE: OK, so that is a clip we found on YouTube of some farmers who control weeds using a flamethrower attached to their tractor, which, honestly, is not an unusual form of weed control for organic farmers. There’s a whole market for ingenious contraptions that can remove or control weeds without using weedkiller — just a couple of months ago EcoRobotix announced that it’s designed robots that can patrol fields looking for weeds, kind of like giant, eco-minded Roombas. Head to howwegettonext.com to check it out, also the flamethrower tractor, by the way, it’s very metal.

Organic farming, sustainability, conservation agriculture. We could go into a lot of depth here about the different schools of sustainable farming, but the bigger point I want to make to you this episode is that these different ideas are only as good as the basic mindset we have about the ground beneath us.

BUZ KLOOT: You have to change the metaphor of soils. You have to change the way you see soils.

DAN CRANE: This is Buz Kloot. Self-proclaimed “soil health nut”, University of South Carolina environmental scientist, and filmmaker — from feature-length documentaries, to YouTube explainer series like “The Science of Soil Health.” But with a background as a chemical engineer, he confesses that he used to view soil as an “inert medium to grow plants — sort of like a factory.”

BUZ KLOOT: The metaphor that that really struck me is there’s a continuum, that on the one side, it’s a medium to grow plants, which is essentially hydroponics with dirt. On the other extent of that continuum would be that soils are living mutualistic ecosystems. When you see things like that, when you see a soil as a living, mutualistic ecosystem versus a medium to grow plants, it changes the way you want to deal with soil.

DAN CRANE: But the larger issue is that the system of modern agriculture is still setup — from government subsidies, to large agricultural corporations focusing research and development, right down to farmers making decisions on which crops to focus on — the system is structured to encourage growing as much as possible in as little space as possible, for the biggest profit. Soil health… that’s not often factored in.

BUZ KLOOT: Essentially what’s happened is that diversity in our farmscapes has really been reduced in the last 30 to 40 years, all in the name of efficiency. And it’s pretty scary, traveling from South Carolina to North Dakota and only seeing corn and soybeans, you know, 99 percent of the crops in the field being just corn and soybeans. I think that leaves us a little bit vulnerable in terms of genetic diversity to large scale disease threats.

DAN CRANE: He sees the soil now not as something inert, but as a dynamic, living ecosystem, and his rallying cry is that other people see it like this, too.

BUZ KLOOT: When we start looking at microbial communities, when we start looking at diversity of crops and species, what I’ve noticed is that this has opened up the minds of many of the farmers around me, and they are beginning to experiment.

DAN CRANE: Oh, and that reminds me. Last episode I said that there were more microbes — bacteria, fungi, and more — living in a handful of healthy soil than there are stars in the galaxy. That was me paraphrasing Fred Kirschenmann.

FRED KIRSCHENMANN: Soil is this living community of microbes. There are more microbes in a single teaspoon full of soil than there are humans on the planet and these microbes have to be fed in order to perform their service of maintaining the health of the soil. And we just have not paid much attention to that.

ELIZABETH BACH: We’re losing a lot of the components of soil that make it productive to grow food.

DAN CRANE: That’s Dr Bach again — and here we are, back at the end of the world. Because this gets to the root of the issue here. We’re running out of soils because, generally, most of us are still thinking of soil as an engine, and fertilizer as the gasoline. The things that soil needs for long-term health, like microbial diversity or protection from wind and drought — they’re less important. But as we’ve already seen, if you exploit soil for long enough, something’s going to give.

Remember when we talked about turning air into food? Well, phosphorus is pretty important too, just like nitrogen — you find it most often in sea rocks, but most potently in animal waste. Guano, the sedimented remains of seabird poop, was a strategic resource for empires and nations of the 18th and 19th centuries — navies would race to claim tiny islands of guano in the Pacific for mining colonies, and Chile and Bolivia fought an actual war over some guano in 1879.

There’s a lot of phosphorus left in the world — we’re not going to run out any time soon. But it’s only in some very specific places. Back in 2015, Ronald Amundson published a paper speculating that we could see phosphorus become a geopolitical issue once again.

RONALD AMUNDSON: So Morocco right now is believed to have something like eighty percent of the world’s phosphorus reserves and probably enough phosphorus for centuries.

DAN CRANE: Are you prepared for the rise of Morocco, the agricultural resource superpower? Because that’s what might happen. But, that said, Ronald is very much not one for sensationalism. He even downplays his own warning about potential “fertilizer cartels” holding the world to ransom.

RONALD AMUNDSON: One of the challenges is, you know, tending to raise an alarm and a concern about environmental issue will appeal to a certain segment of society and create an awareness and a sense of action. But it also tends to, in other people, simply turn them off and generate feelings of simply fighting this or dismissing it.

DAN CRANE: And he’s right. There’s always a balance to be had — you need to know your audience, as much as what you’re convinced is going to save the world. And what you should also know is that many scientists, including ones we spoke to, dispute that figure — that warning that we’ve only got 60 years left until we run out of soil. Not because they deny that there’s a problem — but because they see the positive alternatives taking hold, or they trust human ingenuity over sensationalism. I’ve also spoken to researchers who have seen for themselves the miracles that fertilizers have brought to parts of the world where famine and subsistence farming used to be the norm. We’re going to be looking at this part of the debate in episode four of this series.

But we can’t escape von Liebig’s equation — no matter how sustainable we want to be, we are going to have to figure out a way of growing food that keeps soil as close to alive and thriving as possible, while still stealing some of its nutrients for ourselves. Fred Kirschenmann again.

FRED KIRSCHENMANN: The one culture is, you know, how do we dominate nature, how do we control nature? And what’s behind that is that we have to simply get better at developing better technologies in order to control nature. That’s the opposite of the other culture, which is how do we partner with nature, how do we learn from nature?

DAN CRANE: It feels like the one universal here is that awareness of context — and working within that context — is the best hope we’ve got if we’re going to avoid the death of soil. Whether it’s another Dust Bowl, or through desertification, or deforestation, pollution, fertilizer cartels, whatever. Learning and responding to local context is what Hugh Bennett did to turn back the tide on the Dust Bowl, after all. Maybe it doesn’t sound like enough — but we’re being given the warnings now. The least we could do is listen.

BUZ KLOOT: As far as regenerative farming, it’s almost like we’re in an airplane and we’re trying to change the motor in the airplane. We’re trying to run an active farm and then we’re doing all of these things, and then there are going to be hits and misses, and so it requires discretion. It requires education. I think it requires humility.

DAN CRANE: And what choice do we have? I, for one, do not want to be spending my retirement hobbling around through a real-life The Day After Soil. No thanks.

KENNETH WALSH: These past few weeks have left us all with a profound sense of humility in the face of nature’s destructive power. For years, we operated under the belief that we could continue consuming our planet’s natural resources without consequence. We were wrong.