 Well, thank you for the invitation to come around the world to speak to you tonight. I have a confession to make. I'm not a farmer. I'm not a chef. I'm a geologist. So why would a geologist be standing up here talking to you about soil? That's the stuff that my professors told me to ignore because it covered up all the good stuff underneath. Well, I've spent nights and weekends for about the last 10 years working on the three books that you see up on the screen. And I'm going to walk you through something that shouldn't be possible. I'm going to try and take you through the executive summary of three books in 25 minutes and hopefully teach you something along the way, not just about the lens that I view the world through, which is through my training as a geologist and my experiences, but also sort of the way that soils help support the foundation of civilizations and the way that we treat the land will ultimately affect the way the land treats our descendants. So this first book, Dirt, the Erosion of Civilizations, oops, I can go backwards, hitting the wrong button. The first one is essentially a book that can be summarized with a single sentence, societies that don't take care of their land, the land will not take care of their descendants. It's really that simple. If you look back through history, the way that people have actually treated their land, usually through farming practices, has affected the fate of those civilizations. That middle book, The Hidden Half of Nature, is one that I wrote with my wife who's a biologist. When you think about soil the way I do, you'd recognize soil as the marriage of biology and geology, where the dead world of rocks meets the living world that we all know and enjoy. Soil is where that interface occurs, where it comes together. And what we learned in writing that book was the power of microbial life, the part of nature we cannot detect with our own senses in shaping the health and fortune of the living world that we know. It's about the new science that's been evolving in the last few decades. The book on the right, Growing a Revolution, the most recent one, takes the lessons of history to try and ask the question of how can we actually restore fertility to the land, the science in the middle book, and applies it to the applied problem of actually regenerative farming, intensively farming to grow enough food not only to feed the world, but to do it in ways that restore and heal the land at the same time while making a profit. That's essentially what I'm going to try and walk through. Why would a geologist be concerned about these issues? Well, this map, which shows you the global state of soils, filtered through the fairly coarse lens of a UN report some 15 years ago or so, there's an awful lot of red and orange on that map. Lands where the soils are either very degraded or degraded. We could quibble about what those words mean in this context. I'll do that with my colleagues. What I want to do with using this map is basically illustrate to you that soil degradation is a global problem. It's not just something that affects a few regions of the world. I'll get into that in a few minutes, but it's a global problem. How bad is it? Well, so far, by most estimates, we've degraded somewhere between a quarter and a third of the world's agricultural land to the point where it's no longer in production. And if you want to find places in the world where farming practices has taken land seriously out of production, go to Libya and go to Syria, the places Carolin was talking about in terms of the Roman Empire, those are not places that can today support the kind of wheat yields that we know they had through tax records in Roman times. They've been so degraded as to be virtually taken out of production. In this UN report from a few years ago, it's a problem that's not been solved. We're losing about 0.3% of the world's agricultural production capacity each and every year compounded annually due to soil degradation and physical loss of the soil itself. Now, 0.3% is kind of a small number. It's probably what we're all getting on our savings accounts right now. It takes a while to actually add up to a number that you recognize. But I'm a geologist. I think over 100 year time scales. If you take that number, 0.3% and play it out over the next 100 years, we're on track with modern agriculture to degrade another third of the world's productive capacity at a time when our population is projected to rise by a third. Those two trends are working against each other. It's my contention that agriculture, the way we grow food, has to change this century if we're going to make it into future centuries and be able to sustainably feed the world of tomorrow. Now, if you look back through the history of societies around the world like I did in writing the Dirt Book, what you basically see as a story in which land degradation, soil erosion, has undermined societies reaching back to Bronze Age Europe, to Mesopotamia, the original home of Western agriculture, classical Greece, Rome, the Southern United States, the earliest farming lands in China, various places in Asia. It's a global problem that's been repeated time and again in terms of land degradation. And if you look at that, that has affected the longevity of civilizations. And if you look at that through the lens of most environmental history textbooks, what you'll read is that deforestation caused soil erosion, which undermined societies. I've studied soil erosion in Western North America on steep slopes for some 30 years. And the trees grow back pretty fast if you just cut them down. In other words, the basic villain in the Dirt Book wasn't the axe, but it was the plow that followed. The farming that followed the deforestation was what actually resulted in the destruction of the loss of topsoil in regions around the world. How does that work? I mean, when we think about farming, we think about the plow as sort of an iconic implement of agriculture. But how many native grasslands or forests have you ever been walking around in? Below Timberline, where you see a lot of bare earth. Nature clothes herself in plants. And for simple reasons, that's how you build healthy fertile soils. And so what does tillage do, what does plowing do? It inverts the soil. That makes it exceptionally good weed control. That's why it's been very popular in society after society. But it also leaves the land bare and vulnerable to erosion by wind or rain, depending on what part of the world that you're in. And if you think about soil like we all think about our bank accounts, there's income. There's expenses and there's savings. With the soil, your income is converting rocks into broken up fragments of earth and mixing it with organic matter to make healthy fertile soil. Your expenses are the erosion that removes that soil. And if you're on any kind of a sloping surface at all, erosion's going on all the time around you, although you may not notice it. Every time you kick a rock on a hike on a hillside, you're contributing to eroding that soil. It's the balance between the loss of soil and the production of soil that dictates how much soil is actually on the landscape. And with just like our bank accounts, if you spend soil, if you erode it, faster than you make it, faster than you rebuild it, you're basically running out it, you're burning through your savings. This is what society after society has done around the world and what we're still on track doing today. We're eroding soil faster than we're replacing it. And I'm gonna pick on my own country for a few minutes because I find traveling that's always the safest thing to do. And I'll tell you a story about the American Southeast. Some of the original colonies, Virginia is up here, Alabama's down here, that gray noodle is the Piedmont or Hill Country, the upland country in the American Southeast that was originally some of the most productive farmland in the American colonies. And what this map shows you is the amount of top soil that's been eroded since the advent of colonial agriculture. So that's the net amount of soil loss over the past few centuries. And you notice most of it's gray, which is some four to 10 inches, so pushing a decimeter to a decimeter and a half of soil loss over most of that region, some places where more than 10 inches have been lost. How big a deal was that? Well, when you go back like I have and you read a lot of the original journals from a lot of the original plantation owners describing their lands, they only had six to 12 inches of rich black earth over the not very fertile subsoil. You go to this region today, most of the top soil is actually gone across that whole region. We've eroded it off. It's been documented. How has that played out in terms of farming practices? Not very well. The stuff over here on the right is a soil that's been conventionally managed on a tobacco plantation in North Carolina for the last 100 years. It looks a lot like beach sand. The soil on the left is a soil from actually the forest that's right beside that farm that had been a farm, but was abandoned 120 years ago in sort of part of the great American diaspora westward when the degraded soils of this region helped push my ancestors farther west. We don't teach this in American history classes, but there's a fundamental relationship between the degradation of the land and the American spread across the west, opening up the ear of the dust ball and all those kinds of things. But if you look at these two soils, this one's dark. It's got a color more like chocolate. It's got organic matter in it. The soil on the right looks kind of like California beach sand. And there's a reason for that. It is beach sand, but it's 10 million year old beach sand. It's myosin-aged beach sand. But the parent material of this, the stuff that it's made out of is identical. There are two fields right next to one another. The only difference is how people have treated the land for 100 years, a brief century of farming. It turned stuff that looked like this into stuff like that, and nature was able to fix it in about a century or so. We've degraded soils around the world in this kind of a manner. This one has a lot of organic matter, this one doesn't. We've degraded about 50% of the soil organic matter, the carbon that was in the soil in North America over the last century or two. We've done the same thing globally on average. The numbers are roughly the same. In other words, we've drawn down our societal savings account by about 50% in just the fast few brief centuries. What does this look like at a global scale? Well, we didn't have scientists running around in ancient Rome measuring the loss of soil off of landscapes around classical Greece. I have to rely on archeological data and evidence to do that, and it's always triangulating. So when I wrote the dirt book, one of the things that I did is I basically went to the literature and I compiled how fast are the world's farms eroding? If you look at the, I compiled, I think it was about 1400 different studies to get a global average. They're eroding at a base of about a millimeter and a half a year off of tilled or plowed agricultural fields. Now, a millimeter and a half a year, that's about the thickness of my thumbnail a year. That doesn't seem like a major disaster, does it? Well, it only, it is if you think about how long it takes to erode an inch of soil. That's only 20 years. Most landscapes have about six inch of rich topsoil on them. You could burn through in a century or two, that kind of an allotment of soil if we really put the global average to play. Why does this matter? Because the pace at which nature makes soil is about 2% of a millimeter a year. Takes nature, you know, 500 to 1,000 years to remake that inch of soil in most circumstances. Therein lies the problem. Because what I've just given you is essentially all the math that you need to basically calculate the longevity of an agricultural civilization. Because if we have on the order of a foot or two, a half a meter or so of soil on a hillside and we're eroding it at a millimeter a year on average, you've only got a few centuries before you've eroded that off. When we look at the average longevity of agricultural civilizations, it's about that same time scale with some really important exceptions. Places like the Tigris and Euphrates, places like the Nile in Egypt, places that are big river floodplains where flooding replaces the soil that is lost from erosion. You can actually farm those areas for a long time, but when you get farming up onto the hillsides where you don't have flooding to rebuild the soil, you literally start the clock ticking with conventional agriculture and how long that land can remain productive. So the question of course is, can we restore soil at a global scale? Could we reverse that historical pattern? I started learning that the answer was yes. We could turn this around in a place that you don't expect geologists to do a lot of fieldwork, and that's in my own yard. Because when we bought a house in North Seattle, when I got tenure at the University of Washington, we decided to put down roots in Seattle. My wife and co-author on the Hidden Half of Nature, Ann McClay, was a wanted garden. And what we bought turned out to have terrible soil. We didn't think to dig a soil pit in our yard and actually get in our yard inspected. You'd think we might since we're both scientists and we've worked around the world looking at soils. We got the basement inspected, we got the attic inspected, we got the price knocked down a bit for some problems. We didn't think to dig a hole in the yard, and had we done that, she would have gone, I don't know if I want this place. This has terrible crappy soil. We didn't find a single worm in that soil when we stripped the old growth lawn off of the yard and actually started to think about planting a garden. What Ann realized is that what we needed was organic matter. We had the geological part of soil, we had my part of soil, we didn't have the biology, we didn't have her part of healthy fertile soil. So she essentially took it on herself to conduct what we called her organic matter crusade. She would go to Starbucks and get coffee grounds, bring them back, put them in our yard, compost them, we'd get our neighbor's oak leaves. We got stuff called Zoodoo from the Seattle Zoo, which is exactly what you think it was. They give it away every year. You send a postcard in to basically enter the Zoodoo lottery, basically anybody who enters wins, and they say, come bring a truck, take as much as you want. It's great fertilizer. So we restored health and fertility to our yard by importing organic matter, but now we export organic matter because we restored the yard to the point where the soil is now so fertile that the life above ground is exploding and we don't need to harvest all the organic matter that our plants are shedding to keep the soil built and rebuilt. We've basically turned soil that started like this that looks a lot like that degraded tobacco plantation in Virginia, had about 1% organic matter. We've turned it into stuff that has about 8%, pushing 10% of organic matter, and we did it in about a decade, almost a 1% per year. If you could do that to all the world's farmland soils and you could sustain it for a few decades, we could offset the lion's share of fossil fuel emissions at least for a while. It could have a big impact. Now, the question of course is, can you do this at scale on real farms? It's one thing to do it in a little urban lot in Seattle with the help from the zoo and Starbucks. But we had a lot of other help as well because we realized that what was actually transforming the material that we were adding as compost and mulch to the yard wasn't our efforts. We are setting the stage for the efforts of the life in the soil, the bacteria and fungi that were consuming that organic matter, and then the larger creatures, the nematodes, the small microscopic worm-like creatures and micro arthropods that were consuming the bacteria and fungi that were eating the compost and those things were excreting out in their waste all the nutrients that had been in that organic matter. It was being recycled to be taken back up by the plants. And it turns out to be more interesting and complex than that simple idea of recycling. Because when we learned that, well, we all know that plants taking carbon dioxide and water photosynthesize to build their bodies, give off oxygen for which we should all be thankful. But they also, when we think about roots, they're actually more complicated than straws to just suck up water and nutrients. They basically also push what are known as exudates out of their roots and into the soil. And what exudates are, well, they're things like sugars, carbohydrates. They're things like proteins. Plants even push fats, lipids, out of their roots. What does that sound like? Carbs, proteins, and fats. It's food, right, exactly. Why would plants be pushing food out of their roots? Well, it's not to feed themselves. They already got that covered. But it is to basically feed the microbes in the soil that are doing things in return for the plants. If they were feeding pests and pathogens, for the most part, that'd be an evolutionary dead end. It would not last, persist very long. What's really happening is that those roots, you blow up the area around the zone of a root and the zone around the roots is called the rhizosphere. It's Greek for zone around roots. Plants are actually pushing out those exudates into the soil, those carbs, proteins, sugars, and even hormones and other things. But those plants are pushing them out into the soil and microbes gather around roots the way that students do around pizza and beer. If you want to attract students to something on a college campus, a great way to do it, at least in the States, is to put advertised free pizza and beer. What happens? You get a room full of students. Plants are doing that with microbes. They're putting out a free party buffet and they recruit microbes, bacteria and fungi, that consume those exudates, consume that food, and they metabolize it into metabolites that then are right around the roots that can be sucked back up into the roots. So what are they actually turning that food into these microbes? Things like plant growth promoting hormones. Think about that for a minute. You've got brainless, single-celled organisms in the soil consuming free food that they find in their environment and they're turning it into growth hormones for a plant that's in a completely different kingdom of life than they're in. These kind of symbioses are every bit as complicated, complex, and finely adapted as what occurs above ground between, say, plant pollinators and flowers that we know about, because we can see it and study it with our senses. These kind of symbiotic relationships, mutually beneficial relationships, are happening in the soil, have been happening for the last 450 million years ever since plants moved on to land, the first land fossils that we have, there's fungi wrapped around the roots. These partnerships are ancient and they're important for promoting the health of plants and organisms. So we can think about a plant as having one of two different kinds of diets, either the fertilizer diet where you can feed a plant an awful lot of the key elements a plant needs for growth to maintain high yields and you can do it in crappy soil that doesn't have much organic matter and you can grow big plants, but they're shaded differently because they're not necessarily healthy. Those plants don't invest as much in their root system and you can run this experiment by trying to pull corn stalks out of the ground in healthy fertile soil and crappy soil. There's a lot more roots in healthy fertile soil. That means that plants grown in poor soil are putting out fewer exudates, they're recruiting fewer of those microbial assistants. They're getting less internal way of mineral micronutrients, things like iron and zinc that we need in our diet and they're getting less beneficial metabolites that they need for their defense system and their health. Plants grown in healthy fertile soil put invest more in the root system, they invest more in exudates. There's no, it is no coincidence in other words in our opinion that the global sales of fertilizer going through the roof after the global sales of fertilizer, I'm sorry, global sales of pesticides going through the roof after global sales of fertilizer is not a coincidence because we disarmed with modern conventional agriculture the defense system of our crops, rendering them more vulnerable to pests and pathogens. And there's great studies on this going back to the 1940s. This led me to think about the problem of, okay, how do we actually apply this at scale on farms around the world? Because as I said, it's one thing to do this in an urban lot in Seattle, it's another thing to do it on a farm where the farmer has to remain profitable and stay into stay in business. So I went and visited farmers who had turned soil like this into soil like that and basically did that thing that academics are not very good at. I asked, what did you do? I'd like to listen to you, I'd like to learn from you because I'm a geologist, not a farmer. You teach me how you did this on your land. You do that to enough farmers around the world and a pattern emerges. And the pattern I took away in writing Granger Revolution was the one that's up there. There's three simple principles which I didn't discover. They've been advertised by the UN for a while as the principles at the basis of conservation agriculture and they're quite versatile. It means minimal or no disturbance, so adopting no till, minimizing your disturbance of the soil. If you have to till, don't do it very often. Planting cover crops, keeping the ground permanently covered with living plants to push those exudates out into the soil, maximize the feeding of the life in the soil, and finally diversify crop rotations. Don't grow one or two crops. Now the problem with this, which I think is a fabulous new philosophy to underpin agriculture, is it's the opposite of what we've been teaching in conventional agricultural schools for the last 100 years. When we've basically been teaching people to use a lot of tillage, a lot of agrochemicals and to specialize in growing one or two crops. It's exactly the wrong recipe for feeding the life in the soil. So if you look at what you can do with this kind of a recipe, you can turn soil like this into soil like this. This is an example from the Brant family farm in Carroll, Ohio. It's a farm that grows corn, wheat, and soybeans for the North American commodity markets. It's a conventional farm in the sense that they will use nitrogen fertilizer, they'll use glyphosate, but by adopting those three principles of regenerative agriculture, he's been able to turn soil that started like this that looks a lot like that degraded tobacco plantation into soil that looks like this, a lot like what Anne did to our yard, and he was able to do it in a couple decades. Not quite as fast as Anne did it, but shockingly fast to a geologist. Decades are like round off error on geological time. They don't even count. The idea that we could rebuild soil fertility that fast turned me into an optimist that we could actually solve this problem that I was documenting and writing about in the dirt book. So another way that you can actually help accelerate rebuilding soil fertility is reintegrating livestock onto croplands. This shows you a slide from Gay Brown's farm in North Dakota. He's a farmer who has been reintroducing livestock into the areas where he's been growing crops for farmer's markets. The cows are grazing off the cover crops that he plants between his cash crops, and they're turning his weed control because the cover crops suppress weeds. Any weeds that come up, they just be part of the cover crop. The cows come eat them off before they go to seed, and what he's done is he's turned a weed problem into fertilizer that his cows distribute for free. The chickens that graze on the bugs that live in the cow patties, he sells their eggs. So he used to be buying fertilizer and pesticide. Now he's selling beef and eggs. And he's growing just as much. His yields have gone up, not down. This is not a question of the environment versus the economy or even cheap food versus expensive food. You can actually lower the cost of producing really good food using these kinds of methods. Now Gabe gets a premium for what he sells because it's actually really good food. But what he's done is he's turned soil like this into soil like that. And it has resulted in a farm that has a far lower environmental footprint and is more profitable than his neighbor's farms. And he did it in relatively short order. The key is, Anne and I sort of came up with this catchphrase of ditch the plow, cover up and grow diversity as the sort of the principles on which we could build a modern agriculture that emphasizes rebuilding soil health and the fertility of our land. Now you might put a little asterisk there and go and maybe add cows if you graze the animals properly. There's ways to do regenerative grazing just as there are with regenerative farming. And in 25 minutes, I don't have time to go into that, but I obviously would encourage you to read the book as I wrote it all down. You don't have to remember this. I don't have to remember this, it's great. So what are the benefits of restoring health and fertility to the world's soils? We could actually have higher farmer profits and that's incredibly important because in order for us to eat, people need to grow food in order for them to be working as farmers, they need to be profitable to stay in business. That's what turned me into an optimist on this. You can grow comparable yields. There can be a yield depression for a couple of years as you're turning your soil around and there's less fertilizer, pesticide and fossil fuel use, all of which contributes to that higher farmer profits because if you're growing as much and selling as much, spending less to do it, it's a better business model. Even an academic geologist can tell you that's a better business model. We can increase the amount of carbon in the soil, all those color changes that directly translates into the carbon content of the soil and it can help with water retention, less offsite pollution. There's all these other benefits besides just putting carbon in the soil or making profitable farms. This is one of those few examples of a win, win, win. And there's one other reason that I'll share before I stop in terms of why we should care about healthy fertile soil and that's because it's where food starts. And when we look at what happens between the soil, the life in the soil and how it impacts what actually gets into the food that we eat, there's not a whole lot of data that's out there. We're compiling that for a new book that we're working on that'll be called a You Are What Your Food Eight that'll be out in about a year or so. But this shows you an example, the one bit of data that I'll show you of wheat that was grown on two side-by-side fields, one of which had two years of cover crops and one that was two years of conventional and in the area this was grown, it basically means glyphosate fallow. Glyphosate fallow was the rotation versus cover crops and no herbicides, no chemicals. What this shows you is all the different mineral elements and the ratio of them over there on the right. So ignore all the stuff over here, that just shows you our lab results, but focus on the green line. That's the amount of zinc in this wheat and this is the ratio. There's 56% more zinc in the wheat that was grown with two years of cover crops instead of two years of herbicide. That's about the magnitude of the historical decline of nutrients across the board, the sort of range of 20 to 50%. You can't change the zinc content on the soil in two years, it's not possible. The same amount of zinc was in there in both fields. What changed was the life that could get the zinc out of the mineral particles and into the crop because you can change that in a year or two. It's remarkably fast. So we can restore not only the health and fertility of soil, there's every reason to believe that we could actually grow better food adopting these regenerative practices and that's what we're trying to synthesize with a new book, which hopefully will be about in a year and will hopefully have a better cover than this. And I should stop there, but basically I'll mention that if anyone's interested I did bring a couple copies of both of those books that are out in the foyer for afterwards. Feel free to stop by if you wanna pick one up. And I will stop there and turn it over. Happy to entertain questions later and all this stuff. There's not a whole lot of optimistic stories about the environment these days, but I think what we could do on farms is one of them.