What is essential is invisible to the eyes”, ‎Antoine de Saint-Exupéry wrote in the literary masterpiece The Little Prince. Soil provides 95% of our food and holds more carbon than all of Earth’s plant life and atmosphere combined. Indeed, it enables all life on Earth to exist. So why we barely think, and talk, about it?
Renewable Matter asked this and other questions to David R. Montgomery, Professor of Earth and Space Sciences at the University of Washington in Seattle and author of the “Dirt Trilogy”, a book series about soil degradation and how this intertwines to bigger social and environmental challenges.

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It’s not easy to summarize the key aspects and discoveries of your work because it encompasses different disciplines and crosses a time scale which goes from the birth of life on Earth until the present-day farming methods. What are the three major lessons that you learned from the soil in the past decades?
“The three big takeaways can be tracked along with the research for the three books.
The first one is that civilizations that don’t take care of their soil don’t last and that there is a very profound relationship between the way people treat the land and how the land will treat their descendants. The history of many civilizations follows a common story line. While growing and expanding, most of them failed to safeguard soil health, starting to increasingly degrade the land. This, in turn, led to crop yields’ decline and fueled the need for new land. Eventually, soil erosion translated into an inadequate agricultural capacity to support the growing needs of the population, driving those civilizations to an end. That’s something that hasn’t been recognized enough in part because it plays out in a time frame way longer than most people pay attention to, it’s longer than a lifetime and it plays out slowly, in part because it’s invisible to the naked eye.
The second big lesson I learned, writing the book The Hidden Half of Nature with Anne (Author’s Note: Anne Biklé is an author, biologist and David’s wife), is that the damage that has been done historically could considerably be reversed in a time frame that would be shorter than expected. Life in the soil is the catalyst for rebuilding fertility and microbes are therefore one of the key actors in this process.
The third big takeaway, from the book Growing a Revolution, is that there is a way out of soil degradation by continuing to produce food: it’s called regenerative agriculture. On a big scale, I think what we need is a philosophical change on how we look at the soil, as the foundation of agriculture and therefore civilizations. We need to embrace the idea that rebuilding soil biology and soil health really are the foundation for the future of farming and human life on Earth. The whole biological enterprise of life outside the oceans depends on the nutrients produced and retained by the soil. These circulate through the ecosystem, moving from soil to plants and animals, and then back again into the soil.”

More than half of all terrestrial biodiversity is in the soil, the food we eat and the health of plants (therefore our existence) are, as you highlighted, inextricably related to the health of the soil. You once said that you didn’t learn this in school. Why do you think we don’t study the “hidden half of nature”?
I think it’s because microbial life is invisible, we can’t see it with our own senses, it takes technology to see a bacterium. The relationships between fungi and their plant hosts are hard to understand and were not discovered until the 20th century. It took the development of new technologies, like gene sequencing ones, to unlock the ability to study the interactions between these tiny invisible life forms. Imagine trying to study the ecology of different kinds of bacteria in a community around the roots of a plant. It is below ground so you can’t see it. If you’re going to study and see it you have to dig it up and disturb it and then, anyway, what you do? They are single cell organisms so when you look at them under the microscope, they mostly look the same. The new technologies that came out in the past couple of decades gave researchers the ability to start asking new questions. When it comes to understanding the microbial world, the ecological interactions among communities of microbes work in a very peculiar way: a lot of the beneficial effects of microbes for the health of plants and humans come from the interactions of those communities and that’s even harder to study because you’re not looking at a single organism. Think about the way people interact with groups: if you understand just one person you can’t understand the group.
Another piece of the answer is that soil is underfoot and out of sight. We tend to take it for granted because it’s kind of everywhere and it changes fairly slowly. We tend to study more how to get the most of a crop out of a specific soil this year and less at how to build it over the coming century.”

But the perception and understanding of soil is changing, isn’t it?
“When Dirt (Author’s Note: the first book of the trilogy) came out, in 2007, there was hardly any sort of talk around the idea of soil health. There were people in soil science who were talking about it but there was very little discussion among farmers and agronomists about the role of soil health in agricultural production. It changed. I see a ton of interest today around the idea of soil health, a lot of people interested in trying to learn more about the role of soil biology. Not just farmers but also people coming from other communities, like nutritionists (unhealthy soil is the main cause behind minerals depletion levels in food) and climate activists who are looking at soil as a place where to store huge amounts of carbon, absorbed from the atmosphere. I see a lot of interest from different areas but I still don’t see a whole lot of policy support. There is much more grassroots interest and if you subscribe to the theory of history that you need grassroots interests for a politician to pay attention and start supporting something, then maybe this is a good sign.”

Regarding the climate crisis, the soil could be (is indeed) a great ally as it stores huge percentages of carbon. What’s the potential of restoring degraded soil in the fight against climate change, and how could we do that?
“Soil holds more carbon than all of Earth’s plant life and atmosphere combined and it can hold more depending on the life within it. In devastated soils or with the excessive use of synthetic fertilizers, the balance switches from absorbing carbon to releasing it. Carbon exists in many forms, predominantly as plant biomass and soil organic matter so the two main ways to capture and store carbon are by planting trees and by building organic matter in the soil (Author’s note: soil organic matter is a complex mixture of carbon compounds, consisting of decomposing plant and animal tissue, microbes [protozoa, nematodes, fungi, and bacteria], and carbon associated with soil minerals). It’s a large potential reservoir: if we could increase the world’s soil organic matter content by a couple of percent it would greatly offset the world fossil fuel emissions. It’s hard to do it though because stuff will decay, you have to adopt farming practices that will help rebuild soil organic matter and keep those practices in place. A good way for doing that is to stop plowing, to plant cover crops and to grow a diversity of crops. What that does is it enhances the fungal population and bacteria population in the soil, building up soil organic matter. However, if somebody comes along 50 years later and plows it all up you can completely undo it. It is a powerful reservoir for storing carbon but it’s also a fragile one.”

In the third book of the Dirt Trilogy, Growing a Revolution, you highlighted the fact that one could restore big portions of farmland soil in a relatively short period, reducing fossil fuels and pesticide use, with a higher farmer profit. What are then the main obstacles to overcome to make regenerative agriculture the conventional one?
"The good news is that there is already a solution to the problem of degraded soil by continuing to produce, the bad news is that it is called 'alternative' agriculture.
I think the three main issues for “alternative” regenerative practices to become conventional are knowledge, politics and subsidies.
One of the biggest revelations for me in doing the research for these books is how much the modern idea that we need agrochemical intensive agriculture to feed the world is based on the presumption that we have degraded soils. Indeed, you don’t get major benefits in terms of yields when you add lots of fertilizer to healthy soil.
The conversation among farmers about regenerative agriculture has already started but there are a transition period and costs associated with it. Firstly, you’ll need different equipment to plant your seeds and that’s a very real and not cheap capital cost. Secondly, if you take a field that has been in conventional agrochemical intensive production for 100 years, where the plants are soaked in nitrogen and phosphorus, and all of a sudden you stop applying fertilizer you’re going to have horrible problems: from low yields to unhealthy crops. That transition can take a few years to actually get to the point where the dip in the yield that you get is offset by the lower expenses you’ll have for fertilizer and diesel.
I was impressed with how short that transition can be. What I would love to see is governments start subsidizing the transition to regenerative practices and help mitigate the risk for making that transition. Because most farmers are going to be hesitant to try something completely new and bet their farm on it.
There’s also educational and knowledge barriers to transitioning: a lot of professors of agronomy and farmers alike were trained and educated on the ideas behind modern conventional agriculture of lots of tillage, lots of agrochemical use and intensive pesticide use. Getting people to change how they think about a problem can be very difficult. I see a lot of the interest among young farmers in regenerative practices because they haven’t been trained the wrong way yet. But I see a lot of interest even in the conventionally trained ones who are very much aware that the current farming system is broken. We all need farmers to stay in business because they feed us but we have to ask ourselves what kind of farms we’d like to have in the future and what’s the way to get there.”

It is also a cultural question. One that encompasses a change of focus from individual behaviors to shared duties towards common goals. What trees, bacteria and fungi can teach us about partnering, thinking and acting in symbiosis?
“There’s a lot of good lessons there in terms of the importance of diversity of life. Think about those symbiotic relationships that promote the health of plants: human ability, as a species, to progress was greatly amplified when we started working together and specializing in different things. Our ability to work together in a community is very parallel to what goes on in the soil and also what goes on in our gut. I think there’s a very powerful lesson there in terms of how nature actually works. We have tended to think of nature as competition and things eating each other, but nature is also – and often – symbiosis. The thing Anne and I emphasized in The Hidden Half of Nature is that the symbiotic relationships that are embedded in the very fabric of nature, particularly at the microbial level, are really powerful: they’re an organizing force that we could learn a lot from.
Another big lesson we can learn from the soil in terms of how it works is that recycling is a good thing, that circular economy is Nature’s economy – that the waste product from one organism becomes the input for another. There’s no waste in Nature, it’s that brutally and that beautifully efficient. Everything becomes something else.
The 2015 UN report on the global state of the soil argued we were losing 0.3% of our agricultural production capacity every year, due to soil degradation and soil loss. It sounds kind of small, but if you play it out for 100 years that 0.3% becomes 30%. To me, that’s sort of a very big global policy issue that is on par with questions about the climate and freshwater. But it doesn’t get as much attention because it is out sight.

What do you think about the farm-free advocates that are going all into lab-grown food? What place does technology occupy in soil restoration and the future food system?
We are still learning about what is that actually make the food more nutritious for us. There are compounds that plants make in response to stimuli they get from growing in the soil and interacting with those communities of microbes. Things like vitamins, minerals and a lot of phytochemicals they make have a beneficial effect on human health. We don’t know anything about what problems the new technology will create that will be unintentional and unintended. When modern conventional agriculture was rolled out in the mid 20th century, with its emphasis on pesticides and chemical fertilizers, it was state-of-the-art science, it was going to save the world by increasing the yields and it did the thing it was asked to do. But it also cut the nutritional value of food. Rather than argue that all farming should be eliminated because the way we’re farming now is bad, why we don’t change the way we farm?
Plant-based diets
arguments against meat are based on the assumption that every way we raise our animals is bad. The problem is that if you look at the potential for different parts of the world to produce food for people, a cow does something pretty useful: it turns cellulose into something we can eat. In native grasslands it actually makes a lot of sense to graze livestock and then either eat them or eat what they produce. Now, if the argument for vegetarianism and veganism is based on not wanting to kill a sentient being, it’s an ethical and moral decision, I utterly respect that. But if you ask what kind of food does it make sense to grow where in the world, there are places where it actually makes sense for grazing to be the dominant form of agriculture because water is scarce. The question that is often left out of the arguments about what should we eat it’s the problem of how it’s grown. The answer to whether it helps with the climate or nutrition depends as much on how that animal or plant was raised as it does on what it is.
We need to reshape the nature of our farm economy. That will damage some existing very powerful businesses but also create an opportunity to grow new ones and it’s this turnover that is gonna drive the economy of the future.

Learn more about soil and regenerative agriculture: download and read Renewable Matter #31