The Erosion of Civilization, David Montgomery presentation

The Erosion of Civilization, David Montgomery presentation


[Music] What I like to do tonight is to basically give you an overview of why a geologist like myself would write three books about soil and its importance in human history and what we, I think need to do to actually maintain the continuity of successful agricultural civilizations. In fact this, this trilogy of books about soil that “Dirt” one is the one that looks backwards and looks at the definition of the problem of how we’ve treated land through the ages. The middle one “The Hidden Half of Nature”, that I wrote with my wife and biologist Ann Bikle, looks at the role of microbial life in building soil fertility sort of how it works in terms of soil fertility and the third one “Growing a Revolution”, was the the more optimistic forward-looking book that looks at how we can actually try and address and solve the problems that identified ten years ago in that first book “Dirt, The Erosion of Civilizations”. If anyone wants to live tweet, this that’s our twitter handle encourage you to go ahead and do that. But the big reason why geologists like myself would think to put so much time into thinking about the soil as opposed to rocks is partly on that kind of geologist that works on the surface of the earth. I’m a geomorphologist someone who studies the evolution of topography and most the world’s surface is covered by soil. You get up into the high alpine regions and you get out above timberline and you get out of the world of soil you go to the glaciated regions and the poles you’re out of the world of soil. But most of the world, in the temperate zones, in the tropics is covered by some layer of soil, that I was taught in college to basically dig below it to look at the rocks cuz, that’s what I was training to look at, and the more that I looked at this the more I became to realize that in studying soil erosion around the world, as a geologist, the fundamental linkages between the way the people treat their land how their soil will then be able to treat them over the long run. And if you look at the the UN’s map of global soil degradation today, which is up on the screen at the moment, it basically paints a fairly bleak picture. There’s an awful lot of that orange and that red color, degraded soils and very degraded soils and if you if you look around the world with the sort of the thick fuzzy glasses of a geologist, an awful lot of the world soils our agricultural soils, have been degraded to some degree that has impacted agricultural production. Different parts of the world, to different degrees and to be fair in every one of those red zones that you see on the map there there are farms that are actually building fertile soil. We’ll get back to that later, but this is painting with a very broad brush. We’re actually in not very good shape in terms of our global stock of fertile soil. How bad is that? Well these two studies are the ones that I like to use to actually sort of put numbers on things and if you look at an assessment that David Pimentel and his colleagues at Cornell University put forward back in 1995. They estimated that over the 40 years between the Second World War and the time they wrote their paper, that soil erosion had caused and degradation had caused the abandonment of some 430 million hectares of farmland worldwide. That’s an awful lot of land. That’s an area about the size of China and India combined and it amounts to about one third of all present cropland. If you think about any way you cut, any way you slice the problem of feeding the world of tomorrow. It simply would be easier to feed everybody, if we had all the world’s original agricultural soils at their full native productive capacity. Another way to look at that is what’s sort of happening today and forecasting into the future and two years ago the UN put together a global state of the soil assessment, where they estimated that humanity is losing about a third of a percent of our global food production capacity each year to soil erosion and degradation. And you don’t have to be a geologist to do the math in your head to look forward like, oh in a hundred years that means we would have lost almost a third of our remaining productive capacity for agriculture. In other words it’s going to become progressively harder for us to feed the world of the future if we continue with agricultural practices that degrade the productive capacity of our land base. And it’s in that spirit that I basically will argue to you over the course of this talk that we need to rethink and change the way that we’re thinking about agriculture because I actually think we can solve these problems and I’ll get there. But this is not where I started, I started with a backwards look at the history of soil erosion in the course and fate of human civilizations. That “Dirt, The Erosion of Civilizations” book that got me started in thinking about soils. And when I started working on that I wasn’t thinking about writing a history of farming, that is in the end what I actually wrote. But what I started in thinking about is trying to take archaeological evidence and merge that with geology to try and look at what role soil erosion had played in human history and in past civilizations and in part because I wanted to learn the archeology, I thought it was really cool. I had a professor as an undergrad who taught a little bit of geo-archeology, sort of whetted my appetite for these kind of things and I’d read a book that some of you may have heard about called “Topsoil and Civilization”, that was written by some Soil Conservation Service scientists back in the 1950s. I found it in the bargain bin at Stanford when I was an undergrad it was like a dollar, so I could afford it after tuition there and it was fairly straight, it was an amazing read because it basically argued that one of humanity’s most valuable resources was fertile soil. It was the state of the land and its ability to support agriculture and therefore our ability to feed ourselves and to be able to have people like myself not be farmers and be professors because someone else is growing the food that feeds us. It’s been central to the our history. You know post the development of agriculture that agriculture be successful at a very large scale. And I was very intrigued with the role that soil erosion had played in compromising that success and in looking into the history of soil erosion in societies around the world. I really noticed that there was a, the same story in effect repeated in society after society and soil erosion played a role in the demise of ancient civilizations. You know going back, clear to Mesopotamia and Neolithic Europe, or Bronze Age Europe, classical Greece, Rome, the southern United States, as a story I was never taught in either high school or college that the Mayan civilization, Central America, societies in Asia and more. I could go really down the list which I tried to do in the “Dirt” book because I was trying to be as in that phase of my career was trying to be very comprehensive. And I thought I was on to an interesting story in how the role of soil erosion affected society after society and I wanted to dig through the data the examples to try and see whether or not the idea that I was playing with actually had legs, whether it penciled out, and I’ll share with you some of the data. But let me give away the punchline. You know if a nonfiction book can have a villain, the villain of the “Dirt” book was the plow, and that is something that is you know, it’s a little jarring to hear in terms of thinking about agriculture. I mean you look at the seal of the US Department of Agriculture today, and Thomas Jefferson’s plow is still on it. You know you think about farming or listen to country music and what do farmers do they plow. This is the sort of iconic activity of agriculture and yet in looking back through this history of society after society, I could basically paint a picture with substantial independent support that the invention of the plow fundamentally altered the balance between soil production and soil erosion on those lands that we use to derive our living, to grow our food and that had so increased the pace of soil erosion that given enough time, which to a geologist you know a hundred years is not much; a thousand years, isn’t all that more. I mean if you have enough time to play with, if you’re eroding your soil faster than you’re building it, you’re actually losing it. It’s so I like to use the analogy of one’s bank account, if you spend money faster than you then you make money, you are burning through your savings, and if as I have done several times you complete that process. You know you’re left with nothing in the bank. This is how I started graduate school. And actually how I ended graduate school, so maybe there’s not a message to the graduate students here but, this is a fairly simple analogy, if you think in terms of soil as natural capital. That societies that build their stock of natural capital and invest in the health and fertility of their land are building natural capital. Those that are erode through their soil and its fertility are essentially burning up their natural capital. And so if you think of the soil as a system that can be grown and can be squandered, you’re starting to think about soil the way a geologist would. And i’ll cut through the sort of many historical examples that I go through in the “Dirt” book to basically tell the story of the the American southeast because this is a story that was central to the development of our nation as a country, that I was never taught the connection to soil erosion and farming practices in any of the history courses I took as a, oh in high school or as an undergrad. And this shows you a map of the Piedmont region of the southeast, so it’s the hill country stretching from Virginia up there in the upper right down to Alabama in the lower left and what it shows you is the magnitude of historical soil erosion since the advent of colonial agriculture in the early American colony. And notice that all that gray area, that big noodle that splashes across the map, that’s four to ten inches of topsoil loss over the course of the last couple hundred years. That black area is more than ten inches, and you can basically see that the whole Piedmont region has had at least four inches and up to almost a foot of soil erosion in a few centuries. How big a deal was that? There was only about 12 inches of fertile black earth in this area to begin with and so if we could erode through a third, to virtually all of the topsoil across a pretty broad swath of the original breadbasket or one of the original bread baskets of this country. Think what the Romans could have done with with 500 year run at Central Italy, think of what the classical Greeks could have done with a thousand year run at Southern Greece. You know the idea that long-term erosion under plow based agriculture, tillage associated erosion, that, that could actually strip the soil off of a landscape in a way that could impoverish a civilization well into the future, starts to become not such a crazy idea. And for sort of independent confirmation of this sort of the the potential of that, look to areas around the world today that are perpetual trouble spots in societies that actually went through this process long before the United States was even imagined. I’m talking of course about Syria and Libya. Places where there are Roman tax records that document very high harvests of wheat shipped back to central Rome. Why was that important in Rome’s day? Because the the the Romans had already eroded the soils off of central Italy, and feeding the Roman populace was utterly dependent on the grain shipments from the colonies. There’s this whole long history of essentially societies plowing through their fertile soil and then moving on to fresh new ground and this is exactly what the young United States did, because in the early 19th century, the early 1800s, there was a great migration of people from the eastern seaboard inboard. That was essentially foretold if you will, or predicted by characters like George Washington, back in the late 18th century. He recognized the role of Colonial agricultural practices in degrading the soils of the American southeast to the degree that farmers there were routinely complaining about how depressed their yields were relative to what their grandfathers had had. That they had essentially degraded their land and Washington wrote in a 1796 letter to Alexander Hamilton complaining of this very problem in in the young country. That a few more years of increased sterility will drive the inhabitants of the Atlantic states westward for support, whereas if they were taught how to improve the old, instead of going in pursuit of new and productive soils. they would make these acres which now scarcely yield them anything turn out beneficial to themselves. Well, what Washington was commenting on was essentially the degraded state of soils on the eastern seaboard particularly in the Virginias, and in the Carolinas and he was predicting that the future of America, as a country, lay in moving across the Appalachian to try and take advantage of the fresh soils on the other side of the mountains, on the other side of the frontier at that point. And recall that this is long before any kind of discussion of, you know westward migrations and manifest destiny, the things that historians have reverse-engineered to help explain things. There was a very simple motivation for an awful lot of the westward migration as earliest days and that was the soils on the eastern seaboard had been very degraded and we were in agricultural nation. What does this look like? Well if you go to farms in North Carolina today in the Piedmont country, the hill country and you dig into a the field of a tobacco plantation, which I did over there on the right. That’s the kind of soil that they’re basically growing stuff in. I noticed that it looks a lot like beach sand, the nat, the geology there is effectively beach sand. There’s not much organic matter in, it’s less than a percent. It’s it’s hard. It crusts up the way that that wonderful demonstration showed us a few moments ago. But if you go dig a hole in the forest right near at next door nearby. Which has had a hundred years of recovery from colonial agriculture, you see a completely different kind of soil. The soil type is the same, the parent material is the same, the difference is the role of vegetation and the treatment of the land. The stuff on the left is full of organic matter and it’s much more fertile. And I basically, made this demonstration and thought about the white tablecloth because I was approached by a public television show that was basically running a three-part series on the geological evolution of North America and I got a call late in the game saying Dave, we’ve, we’ve kind of forgot about soil and we need to do something that takes no more than about three minutes to illustrate the history of soil in the United States. That’s kind of a tall order for three minutes. When but when it came down to it I thought that comparing what happened to the soils in the eastern seaboard is really kind of the microcosm for what’s happened on agricultural soils around the country because the latest estimate that I’ve read basically suggests that we’ve lost about half of the organic matter in America’s agricultural soils averaged across the entire country. And in some places like the Piedmont in North Carolina, we’ve managed to farm off the entire topsoil. I mean there are farms that I visited there where farmers are plowing and working the subsoil because the topsoil is literally gone. For those soil scientists in the room they’re really actually farming the B horizon. There’s no O or A horizon left. Now I’m gonna pick on my home state of Washington for a minute here because this this slide basically illustrates to you why geologists like myself would look at what I call conventional agriculture or plough based agriculture full-on tillage as something that is long-term very destructive to the landscape. This is a winter wheat field in eastern, Washington. It’s in the Palouse Country for those of you familiar with Washington, so it’s it’s beautiful list soil, but you’ll notice all those little channels that are cut into it. This is a wheat field that is obviously hasn’t sprouted back out with the new crop and it illustrates the danger of conventional plow based agriculture. In any place in the world where it rains, which it’s hard to find agriculture in places where it doesn’t rain and all those little channels could be erased with a single pass of the plow. They’re easy to rework but the problem is of course is if that happens every year, year after year, it really adds up and this slide basically illustrates that problem. That fence row up there in the upper right hand corner is a fence that the farmer who worked this field, which again was a winter wheat field, that had a wheat fallow rotation. In 1911 when the ground was first plowed, it was up at that upper orange bar and the farmer built a fence line around his water cistern because he didn’t want to plow over his water supply. And the only thing that’s happened in that field for the 50 years after this until the picture was taken in 1961 was those annual rains basically produce little rills like we were just showing you that and the plow itself pushed soil downhill away from the fence line, and I don’t know if you can see there’s a little dark line on the negative, just to the right of that 1961 it doesn’t show up real well, but that’s a five foot high cliff. There’s a stadia rod and negative and that dark bit is a 1 foot interval on it. So what this shows you is that on this particular field over the course of 50 years the farmer lost 5 feet of soil. That’s about a foot every decade, about an inch every year, and I can assure you and we’ll show you data in a moment that there is nowhere on earth that soils naturally form at a pace of an inch a year. That’s an incredible rate of soil loss, and you should also be sitting there thinking of like well yeah but that’s extreme. How typical is this? That’s exactly the right question to be asking because the reason I’m showing it to you is it is extreme and not typical. It’s a really good teaching device that we actually can, through plow based agriculture, lose topsoil it had an incredibly rapid pace. But that doesn’t mean that this pace applies everywhere. So what did I do to try and sort that out? Well of course I went to the library and I started to vacuum up data on what our paces of soil erosion. What are the natural rates of soil formation and what did the long-term rates of geological erosion because in the long-term geological erosion rates must be about balanced by soil production rates, otherwise the world would either be stripped bare of soil or buried under soil because once you start dealing with geologic time if you have any kind of imbalance it’s gonna run away, because of the magnitude, the gross magnitude of geologic time. You run anything for millions of years and it adds up to a really big effect. So I basically went to the library and started compiling data and I’m going to show you two slides full data. The first one has the sort of the most data on it. I’ll unpack it and walk you through it, and then the second one will summarize it, and if anyone’s really interested in all the data behind this I put out a paper in the Proceedings of the National Academy of Sciences that has all the data in it in an Excel spreadsheet. Nobody should ever have to redo this analysis. Just take my data, if you want to update this take the data and start from there, download that spreadsheet. So what did I do I basically uncovered about 1,400 studies that had measurements of both agricultural erosion rates worldwide, in both conventional tillage based agriculture and also in no-till agriculture. And I also found long-term rates of geological erosion rates and the graph here is it’s a one-dimensional graph. So the only dimension that really matters is that x-axis and it shows you rates of soil erosion and what the vertical columns of data are the the rows of data, that just shows you different types of data. So they’re stacked vertically to allow you to compare them visually, the operative dimension is the horizontal one. And notice that each of those cycles that’s labeled as a factor of ten, so it’s a logarithmic scale. It’s just like the earthquake magnitude scale, each one of those steps over increases by a factor of ten and all those sort of white data points are long-term rates of geological erosion, which translate roughly into long-term rates of soil formation and I’ll show you a little bit more data on that in a minute. But the the Cratons that that lower level is something that are tectonically quiescent parts of continents, so you could think most of Australia, most of Africa, outside of the Rift zone, that really kicked our species along. Much of the American Midwest. It would not be places like where I live in Seattle where we have massively destructive earthquakes every few hundred years or at least we hope there every few hundred years. So these Craton’s erode at a pace that gets up to about a tenth of a millimeter a year. That’s really slow. It’s actually really hard to measure something that happens that slowly. If we look at soil erosion rates in the Soil-Mantled world that gets up to about a millimeter a year over in the right hand side. That’s the part of the world that we tend to farm. The rolling hills of Tennessee areas around here out the hills of California that range of you know 1% of a millimeter year to a millimeter a year that’s kind of what Soil-Mantled terrain tends to erode at. The places that erode at pace is higher than a millimeter year are alpine and glaciated drain places like the Andes, the Himalaya, the Cascade Range. Real high steep mountains, not the places we tend to think of as places we would prefer to farm and of course people farm in the Himalaya, but that’s because they live in Himalaya and they have no other land. It’s is all steep there. And so if you then look at those black data points up at the top it’s labeled agriculture. That is conventional plow based agriculture, and it’s from societies around the world different levels of technological sophistication. The common element is reliance on disturbance of the soil as a part of the planting regimen, and if you play the game of sort of which of those geological rates. Modern plow based agriculture is more like, you come to the conclusion that conventionally plowed farms erode like Alpine topography, the average is somewhere over there around a millimeter a year. So if you think about that in terms of soil erosion, we’ve managed to turn places that are relatively flat into places that are eroding like the high Himalaya. This is something that really impressed me as a geologist, that is a global pattern that humanity has imposed on the surface of the earth in the process of growing our food. And it also leads to the conclusion that conventional agriculture is unsustainable in soil mantled landscapes. You look at that distribution of the middle bar and the Cratons the places we actually grow our food, they are to the left of most of that data from contemporary tillage based agriculture. So what does this mean if we boil this down to global averages? This is the second data slide that I promise to show you and this is where we can really start to carry that forward. I mean one of the messages of the last slide is that soil erosion rates are pretty variable. They range by orders of magnitude around the world and even within different geologic categories or within the plow based agriculture. But if we look at the averages and so we have up here up at the top that red number is the average erosion rate, the median erosion rate for the studies that looked at conventional tillage based agriculture and the numbers in parentheses on each of these entries are simply the number of academic studies that were averaged to produce that number. That red number is about millimeter and a half per year on average, and so if you look at the average rate at which our farmland soils around the world are shedding their topsoil, it’s about a millimeter and a half per year. Now if you look at the rate that your fingernails grow, it’s about an order of magnitude faster than that. You know these are slow numbers unless you have a lot of time to work with. And if you look at the erosion rates for no-till agriculture those, it’s about you know less than a tenth of a millimeter a year. Long-term rates of soil production, long-term geological erosion rates that are constrained by independent methods are also you know, they’re closer to 1% of a millimeter a year. Erosion rates under natural vegetation are down below a tenth of a percent of a millimeter a year. I’m not gonna argue to you that any of those blue numbers with this kind of a course analysis, I can argue that they’re very different from one another. The point I want to make is that they are all an order of magnitude or two lower than the rate of conventional soil erosion off of plowed fields and therein lies both the bad news and the good news. The bad news is that we’re eroding our soil faster than its reforming. The good news is that second tier blue number erosion and rates under no-till agriculture. They are actually pretty darn close to long-term rates of soil production. So the bad news is not that we’ve been, that we farm and you know to argue that would be you know that would be a very depressing message to be delivering, but the problem is how we’ve been farming. That we’ve been causing erosion of the very resource that we depend on to be able to maintain our ability to farm. And if you actually take that that long-term net soil loss of about a millimeter a year or so and you play that out over time and take a, do these sort of the back of the envelope kind of calculation that you can do, in terms of how long would it take to literally run out of fertile soil in different regions around the world? Well if you consult the UN’s global soil database, we tend to have about a half a meter to a meter about one to three feet of soil on most hillsides in most parts of the world, and I’m going to distinguish hillsides from floodplains for a reason that’ll become more apparent in a moment. But if you take those upland soils, and you erode them away at a millimeter a year. So it only takes 500 years to 1000 years to quite literally erode through the full stock of soil. And I think that’s what happened in Syria, that’s what happened in Libya, that’s what happened in Greece, its what happened in central Italy. It happened in society after society around the world and one of the problems was it happened slowly, but it played out over time in ways that undercut the ability of those societies to feed themselves. And we are not going to be a, we simply can’t afford to repeat that pattern on a global scale, and if you think about the the civilizations that actually had prospered or survived for thousands of years as agricultural civilizations, most of them tend to be in the major river floodplains of the world, the Tigris, and the Euphrates, the Nile, the Indus, and the Brahmaputra the rivers of lowland China. What are those all those systems have in common, they receive sediment that’s deposited, that’s eroded off their upland areas. They receive fresh soil year after year. So you actually can erode them and maintain their fertility over the long run because there’s an extra recharge term. What happens if you look upstream from those environments in the Zagros Mountains in Iran? It’s not productive anymore. The eastern end of Tibet, it’s not very productive anymore, the soils gone. Somalia and Ethiopia in the headwaters of the Nile, it’s not very productive anymore. So the case that I would like to make is that the numbers kind of pencil out whether you’re looking at the archeological data or you’re looking at modern soil erosion data the numbers pencil out that the argument that soil erosion and degradation actually influence the longevity of ancient civilizations is not a crazy hypothesis to advance. That the numbers kind of pencil out in terms of an order magnitude and as a geologist I find that very satisfying because typically when we get to within a factor of two we think we’re doing great. And this is not exactly news. Back in 1937 in the aftermath of the the Dust Bowl that so ravaged the American heartland. President Franklin Delano Roosevelt recognized this and when he wrote that a nation that destroys its soils destroys itself and I would argue that that argument is as pertinent today on a global scale as it was when FDR made it back in the 1930s. And I also wanted to show you this slide because this is a very famous photograph that is actually part of South Dakota and I put it on the cover of the “Dirt” book and years later when I was starting to look at well how could we turn this around and address the question of is soil restoration possible, can we reverse the historical pattern? One of the first places I came was back to South Dakota to visit Dwayne Beck at Dakota Lakes Research Farm. And why did I do that? I had been speaking at a conference about this the sort of look back through history and Dwayne gave a talk about what he was doing at his farm. And I was so impressed that with what he had been doing and the results that he been able to achieve. That I wanted to go talk to him and see his example of places when I started writing what would be the third book in this trilogy. And as I’ll describe later he took me on a several hundred mile drive around the the region around his farm up near Pierre. And I only saw three plowed fields in tillage season, almost everyone had gone no-till. The problem of essentially blowing dust had been solved in that area by going to no-till and he’d also adopted other methods that I’ll talk a little bit more about a little later, but one of the reasons I wanted to show you that photograph was just my own thinking has been greatly shaped by what I’ve both seen in the historical record for the Dakotas, but also what I’ve seen in terms of people turning this problem around and starting to solve it. But I also learned about the power of soil restoration from my wife in my own garden, well her garden in our lot. I wrote the “Hidden Half of Nature” with Ann and she was the driving force. She’s a biologist, i’m a geologist we started thinking about how could we restore our soil when we bought a house in urban North Seattle and it came with a yard that was covered with the lawn and ever since we’d been in graduate school we’d had apartments, we had little places, where just a little patch of Earth. She really wanted a garden to make a garden because she’s just pined for that for years. She has a green thumb. I call her the plant whisperer. I have a brown thumb. But I’m capable of following her directions in the yard and so things work out. Basically we peeled off that lawn which I like to call an old-growth lawn, an old-growth Seattle lawn, because it had been there for ninety years it had about six inches of ratty roots underneath it and when we peeled that off we found this incredibly rich black topsoil that the northwest is known for. Yeah, no we found glacial till, we found basically nature’s concrete. We live in a part of the country that was overridden by an ice sheet back about 15,000 years ago that had scraped off pieces of Canada, off the Colton British Columbia coast ranges, bulldozed it down to the Puget lowland. Dropped it out in front of the glacier and then ran over it with a mile high wall of ice, compacting it. This is not a recipe for really fertile soil. We had the geology part, plenty of mineral stuff in our soil. What we didn’t have was the biology. We didn’t have a life, whether existing or dead. We just did not have the biology. And you might ask well why didn’t I dig a soil pit and before I bought the house to try and see what was in the yard? At which point i’ll say I don’t know I probably should have, just never thought about it. I’ve done that all over the world never thought to do it in a city. So what happened is that we decided that we needed to basically try and bring the biology to our soil because we all had half the recipe for fertile soil and half that marriage of geology and biology, and we did this in an urban setting by doing things like raking up our neighbors leaves and bringing them back to our lot. You’d be surprised how welcoming your neighbors are when you show up with a with a with a rake and basically volunteer to rake their leaves up and take them away from them. We also used coffee grounds in the back. You know there’s plenty of coffee shops in Seattle they all throw their coffee grounds out the back after work. In part because gardeners come and take it away. It’s a really rich source of nitrogen. So we basically tried to find all the sources of organic matter we could and we composted and mulched our yard quite intensively for years. We started composting our kitchen scraps, we started keeping a worm bin, all the kind of things that you could think of to do to try and restore some biology to our soils. And we’re really quite surprised at how fast we started to rebuild soil because we recall, we started with till pretty much to the surface and this shows you about five years into the experiment of trying to restore the soil in our yard. Those are Ann’s pruning shears over there on the right. It’s a profile, once I finally got around to digging a soil pit when we started seeing the color of our soil change and go from that khaki color to a much sort of a deeper milk chocolate. And this is about five years in, you’ll notice that there’s all this sort of wood and leaf, woodchips and leaves up at the top, but there’s and there’s that till down at the bottom, it’s you know we didn’t, we didn’t rototill. We didn’t dig, we basically just started layering organic matter on the top and we had about two inches of soil after about five years, that just was not there to begin with and this really impressed me. Because if I you know what I was taught in graduate school it took about five hundred years for nature to make an inch of soil. And here Ann had been doing two inches in five years. That’s what four inches in a decade. That’s over a meter in a century and to a geologist that’s no time at all. And so I started thinking like wow what could we really do. Now about ten years into it, this is the soil that we have in our yard in my right hand, over there on your left hand side that’s the soil that we started with we still have some that we didn’t touch, that’s underneath the embankment in front of the under the front window. Less than a half a percent organic matter. The stuff on the right is what we have in our planting beds. And that’s about eight percent to 10 percent depending on where you measure it. It’s a complete transformation in a little over a decade. We were able to increase their soil organic matter content between about a half a percent and a percent a year. Our lot is now a net exporter of organic matter. So instead of raiding coffee shops to grab their coffee grounds, we’re basically contributing to our municipal composting effort because we’re growing more than we need on site to actually continue building up the soil. So this got Ann and I interested in how does this all work and that led us to the world of microbial ecology because it turns out that the microbes, the soil life, were doing all the work in the yard. We were bringing the organic matter in lay it on the surface but they were doing the hard labor of actually turning that breaking that material down and turning it into products that the plants could actually take up and benefit their health. And one of the keys that really helped explain to us how this worked was again something that we were not taught in our college education and that is that when you look at the root system of a plant and you look at the zone around the roots the rhizosphere, the zone of life around the roots of a plant. It, we like to think of it as a living halo. It’s one of the most life dense areas on the planet, around the roots of plants and the thing that we learned that shed sort of new light on this for us, was that root systems are not just straws that suck up nutrients out of the soil to nourish plants. They also push nutrients out of the roots and into the soil. And this doesn’t really make any sense when you think about a plant putting 30 to 40 percent of the of the matter that it makes through the magic of photosynthesis, and they just push it out into the soil. I usually ask this question of you know how many people in the audience take 40 percent of their income and just go leave it on a street corner somewhere. Nobody? Yeah, so far I haven’t found anyone who does that. So why would plants do this? Why would they basically be pushing out so much nutrition into the soil, and why would they you know, why would so many of them doing in so many different settings? They’ve got to be driving some kind of an advantage from it and what they’re basically doing is they’re feeding the microbial life in the soil, they’re feeding the fungi in the bacteria and they’re putting out carbohydrates, they’re putting out proteins are putting out hormones. They’re putting out lipids, fats. We know now from a study of a few months ago. And this really blew our minds in terms of thinking that, Hey these plants are actually trying to feed the microbial life in the rhizosphere. And if plants are doing this and if they’ve been doing this since plants colonized the land, because the earliest fossil plants that we know of have mycorrhizal fungi intertwined with the roots, the kind of partnerships between plants and soil microbes go way back in geologic time. How why would this be so widespread throughout through nature? And basically we came to see the rhizosphere as what we call a biological bizarre, sort of a trading zone where microbes and plants are trading nutrients and metabolites and exudates. The plants are putting out exudates into the soil, those black lines in terms of essentially nutrients that they’re pumping into the soil, and they don’t make it very far. They make it about a millimeter to a centimeter away from the tips of plant roots before they’re consumed by an organism. And what do all organisms do that consume things, they transform them they metabolize them, and then they produce metabolites otherwise known as waste products. But I think waste product is probably the wrong word to use because those metabolites can actually be inputs to other organisms and be actually very useful resources. And what we have an example here of our symbiosis between which, between plants and the microbes that live in the soil, the fungi and the bacteria that live in soils. Because those microbes and their metabolites are producing things like plant growth promoting hormones. They’re producing chemical signals that actually T up responses in the plants in terms of making defensive compounds. These relationships are involved in nutrient acquisition for the plants, those mycorrhizal fungi that can centrally partner with plants are acting as root extensions that can extend out into the soil and mine very particular elements out of mineral particles. Phosphorus for example, they can just nab Phosphorus out, bring it back to a plant, and trade it for what well for a cut of those sugary exudates. The plants are feeding the fungi and the bacteria and they’re getting something in return. It’s essentially a symbiotic style of relationships between communities of organisms in the soil and communities of plants. And I got very interested in what this actually means for how we think about soil fertility. Because it turns out that if you can think about sort of two very different kinds of soils one with an organic, a depleted organic matter to which you add a lot of the macro nutrients that plants need, things that we call fertilizers, like nitrogen potassium and phosphorus and when you do that to plants they put less energy into developing their root system. And if you develop less of a root system, they are producing fewer exudates. And you’re basically feeding different kinds of organisms in the soil or not as many organisms in the soil. And you don’t get as many of the beneficial microbial metabolites that are being produced by those the soil life in the rhizosphere. On the other hand if you’re growing plants in an organic matter rich environment the plants will put out more in deeper roots. They produce more metabolites. They can probably get at an adequate supply of the macronutrients but to be getting more micronutrients and more beneficial microbial metabolites. And we think that there’s something here to the idea that if you’re growing plants on in nutrient depleted soils on a fertilizer diet, you may be able to maintain yields, but what’s in the crop may be different and the health of that crop may be different and it may be more vulnerable to pests and pathogens. The other thing that we looked at in the hidden half of nature are the parallels with what goes on in the root system of plants in the rhizosphere and what happens in the human gut. Because it turns out if you look at the human gut and our relationship with the microbes that live within us, it’s the same system as the rhizosphere inside out this the parallels are actually scary. They’re they’re very clear we go into that in the hidden half of nature. I’ll spare you that tonight because you know I’m a professor, I can talk to a midnight if I really keep going on all this. But if you’re interested in the human microbiome and those relationships, I mean, I never imagined I’d stand from an audience and basically say yeah your your your your gut, your colon is basically the plant root system inside out and actually mean it. But what does this all mean in terms of our view of soil fertility in terms of feeding the world of the future? We face a reality today that you know the human population is projected to expand globally by you know 1/3 to 1/2 again over the next few decades. Much of that population growth being centered in Africa. You look at most of the developed world, and if you know aside from immigration, population is not really rising. If you look at Africa though, most of the projected increase in the human population is going to be on the African continent for the next few decades. What can we do to essentially try and preserve our ability, enhance our ability to feed the world into the future? Particularly in a world where at some point we’re going to be running low or lower on oil and that the fossil fuels that we use to drive agriculture today. And you know we can argue about when when peak oil is, or was and we could argue about what’s going to happen to supplies in the future but I think that the simple reality is is as we start burning through and going farther down the production curve, the price of those inputs is going to go up. We may never run out of oil I think you know arguing that we’re going to run out of oil is kind of scare mongering. Because the more expensive it gets the harder people will look for it and the more will find. The operative thing in my view for agriculture is that as it becomes scarcer, it will become more expensive. And it’ll be harder to actually use as the foundation for our agricultural system. We need to in other words, i’m arguing that agriculture is going to change over the next hundred years. The real question is how it’s going to do so and what style it’s gonna, that’s going to play out. And i’ll argue to you then and argue to anybody really that rebuilding soil fertility would actually be really useful for sustaining agriculture in a post cheap oil and fertilizer world. Whether that happens next year or a hundred years from now. Whenever we get to it we are going to it, we would be very well served if we were able to restore fertility to that one third of global cropland that has already been taken out of production and to restore the full native fertility of the rest of the world’s agricultural soils. That’s what I tried to tackle in the “Growing a Revolution” book, and you know as a geologist I basically decided that my job wasn’t to basically tell people how to do this, my job was to go listen to farmers who had already done it and to basically look at the experiments that have been done around the world by farmers who had regenerated the fertility of their soils, rebuilt the product productivity of their land and try and then stand back and go what are the common elements that underlie the experiments that have been successful in different parts of the world. And so what I did is I visited farms around the world that had rebuilt the health of their soils. And I saw that how adopting all three principles of the system known as conservation agriculture. could match conventional yields using far less oil and chemical inputs. Now what do I mean by conservation agriculture? Well in the demonstration outside before this you basically heard those basic principles. Because those principles are essentially minimal or no disturbance of the soil, so direct planting of seeds or no-till agriculture. It’s maintaining a permanent ground cover to reduce soil erosion and to promote infiltration and retaining crop residues on the surface and including cover crops and rotations so that the ground is covered at all times. So you cut down on that rilling problem, I showed you from eastern, Washington and growing more diverse rotations to both to maintain fertility and enhance that and also to break up the pathogen carryover problem. So there’s three elements, minimal disturbance, permanent ground cover or cover crops, and diverse rotations were the common elements that were behind the practices of the successful farmers I visit around the world in Africa, Central America, and across North America. And why didn’t I go to Asia? I ran out of money simple answer. I exhausted my budget and that had to stop and publish the book. But what did I learn in the process? I learned things about you know things like no-till planters that you don’t get taught in geology graduate school. And I’ll spare you the details of sort of how this works but the Ohio farmer David Brant there’s modeling it for you in terms of something that cuts a narrow trench in the soil you drop a seed and then cover it back up. What I want to really show you is over there on the right. That’s a freshly planted field. Compare that in your mind’s eye to what you get after the passage of a plow. What you saw in eastern, Washington with a freshly plowed field, this field is actually fully covered with an organic dressing. It has a layer of mulch across it. You could rain on that and it won’t erode and it’s just been planted seconds before I took that photograph. If we look at and the sort of technological innovations that allow us to do no-till planting like what I just showed you, we can also think of technologic innovations that can help us with with cover crops. And one of my favorites is the the crop roller that Jeff Moyer and the Rodale Institute have been been and developing and promoting as a way to essentially terminate cover crops and a way to essentially manage cover crops as mulch and to essentially help also with weed suppression in terms of how they’re integrated into crop rotations and cover crop management. So the first stop on my tour actually to visit farmers around the world was Dwayne Beck and Dakota Lakes Farm and why was that? Well, I’d met him as I mentioned earlier at a conference we were both speaking at I saw him speak about his farm and I was I have to go talk to that guy. If I’m actually gonna take this project on i’ve got to go talk to him and learn what he knows and it was an incredible visit. It was very educational for me. And I was really impressed with what he had done in terms of starting with it going to no-till and then going into cover crops and then finally into diversifying his rotations, and now he’s talking about bringing livestock back onto the farm. I thought it was a real example for how we should be thinking about setting up demonstration farms all around the country to investigate what kinds of innovative practices can lead to that could be of direct benefit to farmers. And why I would argue that is that what each basically showed me is that through adopting no-till cover crops and complex rotations, those three components of conservation agriculture. They were able to greatly reduce their inputs of diesel, fertilizer, and pesticide. While at the same time not maintaining, but increasing their crop yields and if you think about a recipe for farm profitability if you can spend less to grow more, that’s a pretty nice recipe. And he introduced me to farmers in the region that had been successful adopting this and their practices also allowed them from going from a wheat-fallow system, where you only used half of your fields per year, to something where you’re the whole farm was in production every year. That’s a huge economic benefit. I came away very impressed, and I asked him hey, this is great. This is you know you’ve shown me farms from a few thousand acres to 20 thousand acres and the Dakotas that have worked could you do this on small subsistence farms in Africa and Dwayne told me well don’t ask me go ask Kofi Boa. He’s already done it. And Kofi Boa is this gentleman here on the right. I love his Got dirt, Gets soil hat he’s got the right idea and he runs the no-till Research Centre in near Kumasi in Ghana. And he’s basically transformed the agriculture of the region around his village and the way that they practice cover cropping and a diversity is actually by growing a diversity of crops in the field all at once. So if you go to their fields they’ll have you’ll notice there’s no bare soil, the basically the ground is cut is covered with a mulch from previous crops but there’s also three or four and up to eight crops in the field at any one time. So they’ve got you know pretty much everything is edible in their fields. They’re not growing cover crops as a cover crop. They’re growing cover crops to eat and they the organic matter accumulates because they don’t eat the whole plant. And what he’s basically done is he’s taken the the subsistence farmers in the area around his village from their traditional slash-and-burn approach to growing with no-till and cover crops in a generation. They’ve basically skipped over the Green Revolution and why would they do that well these farmers had not participated in the Green Revolution. They don’t have any money. They don’t have any resources to buy fertilizer. They have they buy a little bit of herbicide, but they can’t afford to buy much. They can’t afford to buy patented seeds. What they have is their labor and they have little bits of land and what he basically was able to do is shut erosion down. You notice the traditional erosion rate is about 20 times higher than that the no-till with the cover crops. They had horrible soil erosion problems when they’re doing their traditional slash-and-burn because their population had grown enough that they could no longer rotate through different patches of forest. They were basically continually cropping the same pieces of ground year after year and burning it and they’d taken the soil organic matter from four or five percent in the native forests which was actually pretty good in the tropics down to less than 1%. And Kofi, the techniques Kofi taught them basically reduced that erosion but it also look what it did to their yields. It tripled their corn yield and it doubled their cowpea yields. This is as good or better than the Green Revolution did in the developing world and this didn’t in any chemical inputs. It was a change in thinking, a change in practices, a change in the way they managed their land, and it was transformative. 10 years before I visited their village, nobody in the village owned their home. Kofi was relating to me that now almost everybody owns their own home. The economic transformation was sort of the first step in the road to sustainable development. Was basically increasing their yields enough so they were not just feeding themselves, but they had a marketable surplus. I also visited some other farmers across North America. Gabe Brown over there on the left from North Dakota and David Brant over there on the right. I like to show these guys together because they have very different conceptions of what their livestock is. Gabe Brown is has been experimenting with a reintroducing cattle and chickens on to his cropping operation, and it has a big grazing operation. He’ll also tell you that a lot of his livestock is microscopic and underground, but when you go visit David Brandt, he tells you that’s all his livestock. He does not have livestock on his land what he feeds them are his cover crops. And that daikon radish that he’s holding would sell for an astronomical amount in the Farmers Market in Seattle if he could get it there. But David doesn’t want to sell them. That’s the food for his microbes. That’s what he feeds his subterranean livestock. He’s a he’s a commodities corn and soy producer. Those are his cash crops. But he actually plants very diverse fields of cover crops in between his crops and in that picture on the right I want to point out that field across the road past that car all that yellow stuff that’s his neighbor’s conventional soybeans. The green stuff in that field in the background. That’s glyphosate resistant mayor’s tail, it’s not a crop. Up to a third of his neighbor’s fields are covered with that stuff. There’s a real problem with weed suppression in that region, you know how many weeds I saw in David Brandt’s farm none. He plants them, he calls them cover crops. He plants him in between his main crops, then he terminates them and he basically uses them to draw mineral elements out of the subsoil, get it into the soil, and started in the biological recycling. That’s microbial immediated that breaks it down and makes it available to his plants. So he’s basically harnessed weeds in effect and plants a diversity of them and has integrated them into his practices. What’s it done for the fertility of his land and that the bottom line the economics of his farm? I like to share his story on this because he sort of walked me through the whole story of comparing the county average of his neighbors to his operation and basically the county average was full tillage. With adding two hundred pounds of nitrogen a year and two and a half quarts of Roundup per acre of farmland and this is back in 2015 when I was researching the book. And you’d be sort of surprised at how slow the publishing process is to actually get a book out the door. But the total cost to his neighbors that you’re it came to about 500 bucks an acre and that year corners about for yield a bushel from what they were getting and at 100 bushels an acre for that the county average yield. That means that they were losing about 100 bucks an acre on average. That’s a terrible business model and as I was research, as I was putting the the book together in the final throes I ran into paper I think it was also from 2015 that 25 percent of the farmers in the state of Iowa I believe it was lost money on every acre they planted that year. Something is terribly wrong with our agricultural system if farmers working some of the best agricultural land in the world lose money the harder they work. In contrast and I think it’s something is terribly wrong with our soil is the answer there. David Brandt’s been doing no-till for 44 years. Decade or so ago, maybe 15years ago, I forget the actual numbers that’s why write them down in a book. You don’t have to remember them. You can just tell people to look them up later. He went to added cover crops to his rotations, and he’s been diversifying his cover crops. He’s still growing corn and soy as his cash crops but he’s got a very diverse mix of plants in his cover crop mix, up to you know on average 12 and up to 18 I think he was doing In a planting. And he’s doing no tillage at all. He’s using about 24 pounds of nitrogen per acre and about one quarter Roundup and I want to emphasize that only one of the farms I visited on this tour farms around the world was an organic farm. And that was the Rodale Institute to ask them, can you do no-till organically and they said yes they can but they had to do a little plowing every now and then to beat those perennial weeds down and most of the farmers that I visited were conventional farmers who I came to term organic-ish farmers because after they restored the health of their soil they were able to so reduce the reliance on inputs that they were hardly using any at all. And as this as David Brandt’s example showed, he’s using about an eighth of the nitrogen about a fifth of the Roundup. You know that’s revolutionary in terms of his input costs. So he was spending about 320 dollars an acre and his yield was about 80 percent above the county average that year. I believe it was a relatively dry year and this kind of a system does tend to do better than conventional in drier years, and at that $4 a bushel market price he was getting basically a $400 per acre profit compared to his neighbors 100 dollar per acre loss. That’s a really good economic model and that started when I started hearing the same kind of story that when soil fertility had been restored, soil health had been rebuilt, the input costs went way down yet the yields didn’t suffer much after a transition period. This gave me some optimism, cause for optimism, that these kind of style of farming that could rebuild soil fertility might catch on because if there’s one thing that’s necessary is that for farmers to stay in business, they have to remain as a profitable business, otherwise It’s just not going to work over the long run. And Brandt’s example gave me some optimism. Well and the others too gave Brown’s example in Kofi’s example. The economics for people who had adopted this full system of conservation agriculture seemed to work out pretty well over the long-run. Now Gabe Brown likes to show you the soil he says the most valuable tool in a farm as a shovel. I agree completely with him we went around to his neighbor’s farms digging holes, and we dug holes all over his farm And he basically is a very big believer in cover crops as he’s showing off to a group of farmers over there on the right with sort of a diversity of crops, but he’s also been experimenting with reintegrating animal husbandry into his operation. He basically brings cattle in to graze off his market garden and the cover crops that are in there. His crops and his cover crops and then he has chickens that follow the the cattle around to essentially eat the fly larvae that are in the manure and and basically he’s using his livestock as a way to accelerate the breakdown of organic matter, and he’s also developed a sort of profitable side business in selling meat in Bismark. What really impressed me though was the soil.I mean I’m a geologist right? I love cows. I love chickens I like crops. I was really interested in this soil and this shows you the example of his soil versus his neighbor’s soil. His neighbor’s farm that we’re comparing here is an organic farm. It’s been organic for a long time, but it’s plow based. It’s a tillage based organic farm, so guess which one of those two is Gabe soil and which is this organic neighbor’s soil? Gabe is not an organic farmer. He’ll still use chemicals when he needs to he just doesn’t find the need to use very many of them very often. His soil is that black stuff on the right you you you basically compare them. It’s like night and day. One is very a very rich very fertile soil the other is a degraded organic soil or a degraded soil that has been managed organically. And one of the key things that I learned out of researching this book and they really will emphasize in the book is that many of the arguments that we tend to have about conventional agriculture versus organic agriculture. They get cast in a whole different light when you think through the lens of soil health because neither one of those really map onto degrading soil or building soil. It’s different and these principles of conservation agriculture can actually help build soil fertility in both organic systems and in conventional systems. And so I was challenged at one point by my wife and by my editor to basically come up with a catchphrase that captures the the spirit of conservation agriculture and I frankly I don’t remember which parts of this Ann came up with and which parts I came up with but what we landed on was Ditch the Plow, Cover Up and Grow Diversity as the simplest phrased advice we could give to farmers around the world in terms of how to implement conservation agriculture. Now you’ll notice that there’s nothing specific about how to do any of those. These are broad principles. These are the kind of things that worked across the board for the farmers that I visited and the way you would do this in Ghana would be really different than the way you would do it in the Dakotas. The idea is to try and take these general principles and figure out ways to tailor and adapt it to different environments around the world. Different levels of technological sophistication. Different kinds of soils, difficult climates, the whole yada-yada-yada of what’s different and unique about my farm versus your farm versus their farm. But these principles I think are actually fairly transparent and universal, and they have room for bringing in animal agriculture as sort of an add-on and benefit from this. But I’ve saw farms that rebuilt the fertility or soil without that, but I also saw farm where I think that that greatly accelerated it. And this was eye-opening for a geologist who had studied gully erosion in the California foothills and basically documented that when the Spanish arrived with cattle the gullies cut down to bedrock. They were a horribly destructive force in California. I was incredibly impressed with the ranches that I saw where people were using a livestock as a tool of soil restoration and regeneration and it boiled down to me realizing that oh the problems not the cows, the problems how we’ve been managing the cows and that it was essentially a social and a management issue. Well what are the benefits of conservation agriculture? You know comparable or increased yields, that’s important going forward. We can’t afford to go to styles of agriculture that lower our yields greatly. It reduced fossil fuel fertilizer and pesticide use those are all of benefit, for multiple reasons not the least of which is the lower cost to the farmer but also to the lower pollution that’s produced off-site. They can increase soil carbon both in terms of building up soil fertility and also for carbon sequestration. They also increased water retention and therefore crop resilience. You saw an excellent demonstration of that and the lead in introduction to this talk. But they also result in higher farmer profits from lower input costs that maintain yields over the long run. That’s a recipe for wider adoption and for better farm economics and I actually think that we should be pursuing policies at a national level that really prioritize rebuilding soil health as sort of a natural infrastructure project that could help build and keep wealth in rural communities across America by keeping more of our farm dollars actually on the farm. So what does this mean? More philosophically speaking at a university and as a professor I’ll engage in a bit of history for a few minutes. I think we’re at the cusp of a new revolution in agricultural philosophy. If we look back through the four revolutions in agriculture, we’ve had to date. The first was the idea of cultivation and tillage in the first place, that was revolutionary. It started us on the path to where not all of us have to farm to feed ourselves. As we talked earlier and then talking about the “Dirt” book the the embrace of tillage based agriculture came with serious downsides over the long haul but it was really the first agricultural revolution. The second was the recognition of soil husbandry, the idea of putting legumes and crop rotations, planting cover crops. In societies around the world independently discovered this for themselves because it helped bolster soil fertility and that quote from Leonardo up there is about as true today as it was 500 years ago. And think about the rest of science how many areas of science can you say that about? We still do we still have a lot to learn about soil science in the role of soil ecology in soil fertility. The third agricultural revolution in the way that I keep score on these things and most academics have their own scoreboard for these kind of things so you know if you disagree that’s fine. The third revolution in my view is was mechanization and industrialization that happened that brought in sort of the modern fertilizer industry and the mechanization of farm implements and the replacement of animals and animal husbandry and its displacement off of farms and that gentleman up in the upper right Justus von Liebig is a very interesting character. He’s the person who’s widely regarded as the Godfather of the modern fertilizer industry. But what hardly anybody knows is that he wrote a book near the end of his life, 23 years after he wrote the book that sort of introduced the idea of adding particular chemical elements to farm fields to fertilizer crops, he wrote a book that basically cast his view of how to sustain agriculture in completely different light. It’s called the Natural Laws of Husbandry. And it basically is Liebig reflecting on a career in both chemistry and agriculture where he recommended that the way to sustain agricultural production, to sustain soil fertility over the long run, was to return organic matter to the fields. Because if we didn’t do that we wouldn’t be providing a full complement of nutrients to our crops. And he was sort of the first person that recognized the overarching need to sort of close the loop in terms of nutrient cycling. Somehow we have to rebuild or replace the fertility of our land as fast as we’re degrading it, otherwise we’re gonna essentially wear it down. This was something that I think that very few people sort of recognize in the history of agriculture in terms of how different a perspective Leibig ended his life with than what he’s famous for. The fourth agricultural revolution really I mean you got to point to the Green Revolution and biotechnology. The sort of the late half of the 20th century in terms of the modernization of our agricultural technologies, you know and and wheat yields in developed countries has shown there and that graph were doubled as a result of the Green Revolution. You know crop yields went up in the 20th century without question. The challenge that I think we face today is thinking through what are we going to do next? Can we actually continue doing more of the same and expect to see comparable results or do we have to think through a different filter and think differently about the future of agriculture. And of course i’m arguing that the next agricultural revolution will be thinking about soil health and thinking of recasting the way that we think about farming practice the way we think about soil through the lens of thinking how can we build soil fertility as a consequence of intensive agriculture, rather than mining it as we have done in the past. And to do that basically I would argue we need to combine the best of modern technology with the best of ancient wisdom. The ideas of crop rotations and cover crops are not new ideas. These are ideas that were discovered independently in societies around the world because they helped bolster soil fertility. What we need to do today is marry them with the technologies that allow us to practice no-till and to minimize soil disturbance and get all three elements of conservation agriculture working together. Because the this the farms I visited and the studies that I have reviewed, the few studies there are of those whole system of practices really point to a synergistic effect of adopting all three of those elements, and why do they work because you’re essentially cultivating the beneficial life in the soil. You’re not disking up and plowing up the mycorrhizal fungi. You’re basically feeding carbon, and nitrogen to the soil, which base essentially acts as currency in the underground food web, and you’re basically not creating opportunities for pests and pathogens by diversifying crop rotations. And I’d like to emphasize that this is not really the question of you know in terms of the future of agriculture, of a low-tech organic approach versus a high tech or Agrotech or GMO approach. You know we’re really talking about a third dimension to the arguments that we tend to have on the to that two-dimensional plane. It’s really I think about understanding how we can apply soil ecology to the problem of sustaining if not increasing crop yields in the post-oil low input world. At the key there is thinking about soil ecology and trying to actually work with the microorganisms that are in the soil to benefit our farmers and our productive capacity and if we look at soil through that lens we come to a very different set of of thinking about the way that we should be conducting agriculture. Because if you look at the dominant sort of paradigm for 20th century agriculture in the developed world, it was intensive tillage, intensive chemical use, and monocultures, growing one or two key things. If you look at the principles of conservation agriculture they flip all three of those completely on their head 180 degrees. To basically stop plowing, always keep the ground covered with cover crops, and to you know basically use biological methods to fix it a lot of nitrogen, maybe not all of it, but a lot of it and actually diversify up crop rotations. It’s a 180 philosophical shift, and it doesn’t involve any particular product. It is a switch in practices that could lead us there I would argue. What are the potential benefits from? Enhancing soil health I think you really help us with with some of the really big challenges of the 21st century. Of course the idea of feeding the world and not just doing it for the next couple decades but how we’re gonna do for the next few centuries as we play out in the post oil world however that plays out. We can also help us actually park a lot of carbon in the ground. There’s wildly varying estimates about how much carbon we could actually park in the world’s agricultural soils but even the low end estimates are a lot. Not enough to solve the atmospheric CO2 problem but in my view at least but enough to make a serious dent in it and we should be doing it simply to maintain the fertility of our land in the first place. The practices you would adopt are identical. It could also help with environmental degradation if we look at the biodiversity loss in the continents for example the future of what happens on farmland is a big piece of the biodiversity problem because foreign land accounts for a quarter the continents. You know what we do on farms in the future is gonna have a big effect on who we continue to share this planet with in terms of the the animal and plant world’s. And importantly I think that rebuilding soil health can actually help restore farm profitability. This is something I hadn’t really been aware of when I started doing the interviews for “Growing a Revolution” but what I heard in story after story of farmers who had adopted these practices and maintained them over time was it had worked out pretty well for them. There were rough spots of course as there always is in any transformation but that it had worked and that gave me some optimism that the short-term incentives for farmers are starting to align with the long-term interests of society as a whole at maintaining the fertility of our soils. So I think we have a major natural infrastructure project that faces us as a species in terms of rebuilding the fertility of our land but it’s one of the most important investments humanity could make in our own future. I think is rebuilding the fertility of our agricultural land and there and I think we have opportunities to try and build coalitions between the developed and developing world between rural States and urban States. We really all have a stake in this and I can’t really think of a great rationale for not at least trying to experiment and push these ideas forward to the extent that they’re able to. Is it gonna solve all of our problems? No, but it could really help with a whole basket full of them and basically, I will stop there naturally as any author will do I’d recommend that you read read my books every authors gonna tell you that but anyway thank you so much for your attention and for the invitation to come and address you it’s a pleasure to be back in South Dakota. I’ve learned an awful lot from a lot of really cool farmers here. Thank you (applause) (Music)

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