THE MICROBIOME SUMMIT : The New Path to Health
Replenishing the Soil So It Replenishes Us
Dr. David R. Montgomery, PhD
Dr. David Montgomery is a geologist and professor of geomorphology at the University of Washington. With his wife (and fellow Town Hall Medicine Speaker Anne Biklé), Dr. Montgomery wrote a book called The Hidden Half of Nature, and expanded on the topic in Growing a Revolution: Bringing Our Soil Back to Life. In this interview, Dr. Montgomery talks about how soil degradation is arguably the biggest, least recognized problem that humanity is facing today. Microbes are an important part of healthy soil, and by nourishing the microbial life in soil, and cultivating the beneficial microbes that the plants naturally evolved with – soil can be made fertile again.
- Tracey:
- Hi. Thank you for joining me, Dave.
- Dave:
- Sure. Pleasure to be here.
- Tracey:
- So, you and your wife, wrote this incredible book which I found so absolutely fascinating, especially the way that you were able to bring life back to your garden. You, essentially, in Washington State bought this house and your front yarn was glacial till. And you were able to, through harnessing the power of the microbes, bring it back to life. Can you explain how, you and Anne did this?
- Dave:
- Yeah, what I should first say is, it is mostly Anne’s work that did this. She’s the gardener and the biologist. I’m a geologist and in looking at the process of how she restored life to this really sort of decrepit lot in North Seattle that had a 100-year old lawn when we bought it, with nary a worm in it at all, we peeled the lawn back to make the garden that Anne desired and there was no microscopic clay. We couldn’t see, no bugs, nothing we could see. It was, it looked like compressed beach sand which is what glacial till effectively is. It’s pieces of British Columbia that got scoured out by a glacier, bulldozed south about 15,000 years ago, dropped in Seattle and over-run by a mile-high wall of ice that’s about three times the height of the space needle, if you’ve ever been to Seattle. And that’s not the best soil to grow anything in and so when we peeled that lawn off and saw that we have the mineral part of soil, not in terribly good shape, without the biology of soil …
- Tracey:
- Right.
- Dave:
- … Anne took it on herself to really try and bring organic matter back to the yard and try to bring life back to the yard. Originally to try and mulch the yard to try and keep moisture in because we were planting in August. Even in Seattle, rainy as it is, August is really dry and it’s not the best time to try and plant plants. What we didn’t realize at the time was that over the course of the next few years, bringing all that compost and mulch and organic matter back to the yard and layering it right on the ground surface really gradually started to transform that soil and build rich, fertile soil. Now, 15 years down the road, the yard’s been totally transformed, the soil’s been totally transformed and we watched what that did to the life above ground and really came to realize the power of life below the ground to rejuvenate life above ground. And as we looked into that and asked the question, “How could this work so fast?” To a geologist you know there’s something that could happen in, you know, five, ten years and be noticeable changes for the better. It’s instantaneous, to a geologist. It’s just off scale for someone like me. Looking into explanations for that led us right to the role of microbial life in breaking down and reprocessing once living matter, organic matter, dead things, into the raw materials to support new life. And, as we looked into that, we really realized that it’s not just that simple but there’s all these partnerships that go on in the soil between the microbes and the roots of the plants that are deeply rooted in evolutionary relationships that we didn’t learn about when we were studying soil science in graduate school.
- Tracey:
- Right. Yeah.
- Dave:
- Studying the microbes and their power to actually transform larger organisms, plants, eventually led us to look at their role in human health as well.
- Tracey:
- So, what are the microbes doing below the soil that they’re able to grow these luscious plants?
- Dave:
- Well, you know, there’s really sort of two things that are going on there. One is the microbes are essential to breaking down the organic matter, recycling the remains of once-living things. Like, you know how in the fall you have deciduous trees, they shed their leaves and they fall to the ground and they rot. The trees are not just wasting that stuff. They’re putting it into play in nature’s recycling system so they don’t have to support that living matter over the winter when they have a hard time doing it. But they get access to all the elements in that, come spring when that material starts to rot and break down, it’s the microbes that are the driver of that part of the wheel of life, if you will, the cycle of decay. Fungi, in particular, will break down cellulose, rich things and woody things. Bacteria will help consume and break things down. And they’re essentially reprocessing and repurposing the complex molecules that were in once living matter into simpler forms that can be taken back up as nutrients for plants to build their bodies anew. So, that’s one half. They’re essentially nature’s recycling system.
- Tracey:
- Right.
- Dave:
- Think about all the elements that go into make a plant. You get carbon, hydrogen and oxygen from water and CO2 in the air through photosynthesis. The nitrogen from with the help of microbes that are living in their roots. Everything else that goes to make their bodies, all the micronutrients, the things that we need also in minute quantities for our health ultimately came out of rocks and that happens really slowly through the breakdown of rocks and microbes help drive that process and they drive the recycling of that material once it’s in the biological world. They help keep it in play, going from living matter to decaying matter, back to living matter. But the thing that really surprised both Anne and I, I think, in looking into the role of microbes in the health of larger organisms was the role that they play in partnerships with those organisms and how did that work? Well, what we learned looking into the role of the soil is that that plants don’t keep all the stuff they photosynthesize, all the carbohydrates and the proteins they can make using their ability to harvest solar energy. They don’t keep it all for themselves. They will share it with the microbes in the soil by pushing it out of their roots into the soil. And it seems like kind of a wasteful thing to do if you just think from the sort of, the selfish energetics of a plant, what they’re really doing is they’re recruiting microbial allies in the rhizosphere, the zone of life in the soil that extends about a millimetre to a centimetre around the root hairs of most plants. What the plants are doing is they’re recruiting particular microbes that consume those exudates, the carbohydrates, the proteins the plant’s pushing out into the soil. And when they consume them, they transform them into their waste products, metabolites, that polite word for microbial poo, their waste. And it’s really interesting when you look at what some of those metabolites are. Because some of those microbes in the soil are metabolizing those sugary, sugar-rich exudates, putting back into the soil compounds that promote the growth of plants. A plant grows hormones, for example, and other compounds that assist in plant defence. And who would have imagined that microbes living in the soil would be making plant hormones? They’re not plants. They can’t benefit from that. It’s an example of a symbiosis where the plant is essentially feeding the microbes and the microbes have adopted the role of kind of an offshore chemical factory for the plants, making compounds that boost the health and growth of the plant. Those kind of relationships turn out to be near ubiquitous and really define, in many ways, the relationship between soil life, soil microbiota and plant life. And the more people that looked into this in the last couple of decades, just back when Anne and I were in graduate school, this stuff was not really known very well. But our way of looking at microbes has totally flipped from just looking at them as pests and pathogens to now realizing that certain microbial communities are actively recruited by plants and that they help maintain the health and growth of plants and thereby effectively the fertility of the soil. So, the more we’ve looked into this and sort of watched our garden transform before our eyes, I should say Anne transform our yard into a garden. We really realize the power of microbial life to really affect positive change and it made the ways that we tend to look at microbes into an agriculture and, as it turns out, medicine have been too narrowly defined by the world of looking at germ theory, of thinking on them as pests and pathogens. We know that both in the botanical world and the zoological world that in human health pathogens are a real issue. But most microbes are not pathogenic and, in fact, a surprising number of them can enter into partnerships with us in ways that we’re only now understanding.
- Tracey:
- I love the partnership word. It just seems like they have this community that works so symbiotically together. Yeah.
- Dave:
- Yeah, if you think about it, it’s kind of analogues at the human scale. You think about a village of people, a city of people. We don’t all have the same job; we can diversify and specialize in doing different things and by working together we can actually get more done more efficiently than if we all had to do everything ourselves. You could think of a microbial community as a sort of a similar way, as communities where if each microbe has a strength, a particular set of chemical reactions that they’re really good at doing, if you get different sets of them working together they can actually define a system that can be robust and stable and mutually beneficial in ways that can create partnerships with plants or, indeed, with people within our own bodies as it turns out. Thinking of those kind of relationships is a really different way of thinking about our relationship with the microbial world.
- Tracey:
- Now, Anne did a few things that were pretty cool. I just had this vision as you described it of her, like, driving around to the various Starbucks and getting all the coffee grounds and then she made this compost tea and she would really try and feed the microbes and take care of these microbes.
- Dave:
- In a way, she almost turned into a microbe rancher, someone who was cultivating microbial life. And when she started doing that I don’t think it was intentional to do that initially but the more we got into it the more she started realizing that actually that was what you needed to do to feed the soil. You need to feed the microbial life and so you think, what do they actually eat? It’s organic matter. Decaying things. So, she would, like you were saying, she visited lots of coffee shops in Seattle and would be behind a coffee shop. They all put their coffee grounds out behind the shop in an afternoon or evening and gardeners love it because it’s a good source of nitrogen. And, you know, if it’s there to be had it’s better not to waste it. You can put it back into the soil and help rebuild fertile soil. And there’s other sources that are carbon-rich sources. Leaves. Oak leaves, for example, are a good source. One of our neighbours had a few oak trees that every fall would shed a bunch of leaves and he was more than happy to have us show up and rake them up and take them back to our yard. So, the idea of cultivating microbial life in many ways boils down to bringing organic matter back into the system. You can look to nature for analogues for that. You look at, say, tropical rainforests and what happens to the trees that fall over and decay, or the leaves decay. They rapidly get recycled by microbes into new life, into organic matter and then back into living mass above ground. In the more humid regions of the world the carbon that’s produced, the carbon-rich stuff, the humus produced will stick around for longer in the subsurface and build up rich, fertile soil. To give an example of trees shedding their leaves in the fall, deciduous trees is another way plants are trying to return organic matter to the soil and the microbes are essentially driving the processes that can convert that matter back into the compounds to be taken out to support the growth of new life. When you start thinking about the little microbes in that kind of cycling, the idea of building up their ability to do so really supports the health of life above ground because that’s essentially how in part how you’re getting nutrients into plants, is through that microbial pathway.
- Tracey:
- Can you explain the global issues that we’re facing right now. We have to feed soon to be nine billion people and we’ve got great issues of how to care-take our soil. Can you explain some of your thoughts on that?
- Dave:
- The problem with soil degradation is arguably probably the biggest, least recognized global problem that humanity faces because where does most of our food come from? Ninety-seven percent of our food comes directly or indirectly from the soil, how we treat the soil. So far, over the course of human history we’ve degraded between a third and a half of the agricultural land that we’ve so far worked. I wrote a book called Dirt: The Erosion of Civilizations about 10 years ago that looked into the problem of soil erosion and degradation and how that has influenced the course and fate of human societies. You can make sort of a short summary of that by arguing that the way people treat their land in the end has set how the land can sustain them or not over the long run. Look at societies around the world that have either eroded or degraded their soil. They can lapse into long-term poverty. And if you look at what we’re doing with modern agriculture today, it’s continuing the process of degrading the soil. We’ve made great strides at limiting erosion. We still have problems with erosion on a global scale but the other aspect of the problem is the degradation of the soil life. The organisms that actually were maintaining the fertility of soils over the long run, we’ve now adopted practices that substitute the natural processes of vegetative return to the soil, the decay of that matter, mediated by the microbes. We’ve substituted the processes of, well, we’ve substituted chemical fertilizers and pesticides in combination with the plow. Those three things very much degrade life in the soil and alter its ability to maintain the processes that lead to the fertility that we’re relying on to actually feed ourselves. And we’ve just really started to learn how these things work. Many of these things were suspected back in the 1930s and sort of the dawn of the organic agricultural movement. People like Sir Albert Howard and Lady Eve Balfour started arguing about the role of microbial life and mycorrhizal fungi, in particular, at delivering nutrients and micronutrients especially to our crops and the way that plays through into human nutrition. The mechanisms through which those connections worked weren’t really understood until much more recently, the last couple of decades. A lot of the science in terms of how microbes work has started to fill in the gaps, the mechanisms about how those connections actually work. In the meantime, we’ve transformed our whole system, our global agricultural system into one that’s very much dependent on the plow, on nitrogen-based fertilizers which consume about five percent or so of the world’s natural gas supplies to make. The connection with the growing dependence on insecticides as a result of that is something that scientists are now filling in and establishing the connections between. It turns out that those microbes that are in the soil that are partnering with the plant roots, that are helping make those plant defence compounds, were actually central for maintaining the health of crops. By altering soil biota we essentially changed the vulnerability of the very crops that we depend on for our sustenance to pests and pathogens and disease. Now, it turns out there’s ways to try and get around that in terms of different agricultural practices that cultivate microbial life and this is where Anne’s experiment in our garden, transforming it from essentially biological death to a real fountain of fertility, if you will, really opened my eyes to thinking about agriculture in different ways. I spent six months last year travelling around the world interviewing farmers who adopted practices that essentially are geared towards cultivating life in the soil, microbial life in particular. Looking at, what are the common elements between farms in different parts of the world, subsistence farms in Africa, coffee plantations in Costa Rica, corn and soy commercial farms in Ohio, and livestock operations in the Dakotas, that actually work to rebuild fertile soils as a consequence of agriculture. And something I’m very excited about at the moment is a new book coming out in May called Growing a Revolution: Bringing Our Soil Back to Life that talks about those experiences. It simply boils down to three simple principles: don’t disturb the soil, so no-till or minimal tillage; plant cover crops that include legumes to bring both nitrogen into the soil and to act as a natural weed suppression; and then also grow diverse rotations. Don’t just grow corn, corn, corn or corn and soy, corn and soy, because the pests and pathogens figure that system out pretty readily. But if you have at least four different crops in your rotation you can get, not necessarily get completely off the agri-chemicals we rely on today, but start rebuilding soil fertility and greatly reduce our use of inputs such as diesel, fertilizers, insecticides and herbicides and yet maintain yields. There is a couple of year depression in yields of a few percent in the transition. It would be difficult if you’re not a very over-capitalized farm for example but there are farming practices that actually bring soil back to life. And they’re basically all rooted in this idea of cultivating the beneficial microbes that plants naturally evolved with. It’s a different way of looking at farming. Really enthused because it seems like it really works and it’s not quite organic farming. Organic farming can be this way as well but in principal to transpose both conventional farms and organic farms and make both of them more sustainable … but that’s not the kind of discussion we’re having around agriculture today. We tend to go to our corners and argue about other issues when I think this is one that we could all agree on, in part because it improves the bottom lines for farmers. The only people who could really lose out are the middle men who are selling things to farmers.
- Tracey:
- Right. But it also focuses the conversation back on something that is invisible, that we’ve never really thought about before and that’s the microbes.
- Dave:
- Yes, exactly. And it’s so hard to actually think about something that you can’t see with your own senses. I mean, I’ve never seen a microbe with my eyes and neither has anyone else. We need some kind of technology to actually access them. And to think that there’s a trillion little microbes living within you is a really strange thought if you’ve never encountered them, or that there’s a nonillion microbes on this planet with us. That’s a one followed by 30 zeroes. That’s enough microbes to stretch them all out from Earth to Alpha Centauri and back. This planet is riddled with life that we can’t actually see and that’s where the title of the book that Anne and I wrote, The Hidden Half of Nature, is literal. If you weigh up all the microbes in the world they would account for about half the biomass on the planet. So, think of every plant, every animal, every person that you’ve ever seen – there’s an equal weight in this hidden half of nature of life we’re just beginning to understand. And it turns out that many of the connections between microbial life and the so-called higher life forms of plants and animals and people are rooted in symbiose that are mutually beneficial. And that’s really a different way to look at nature. It’s not to say that everything is, like, completely happy and hunky-dory and kumbaya in the microbial world. There’s a lot of competition. You know, the microbial world, it’s the process of recycling dead things that leads to the growth of new life. It’s not a conflict-free kind of relationship but they’re set up in many ways that benefit the stability and resilience of the more complex organisms that the microbes have partnered with. And why does this benefit the microbes? They get more stable habitat. Why does it benefit us? It enhances our abilities, and I’m sure Anne will talk about our ability to do things both in our own bodies and in our agricultural fields. If we took the idea of cultivating the trillions of beneficial microbes per square metre of farm field we could have all these allies who work 24/7 for us for free with the only price that we need to actually feed them with the kind of materials that they need to produce the metabolites that benefit the crops that we need.
- Tracey:
- Right. For our home gardeners out there, in summary what would you tell them to start doing?
- Dave:
- I would suggest following Anne’s example that she led with in our yard. Try and increase the organic matter in your yard. What that can mean is returning things to the surface of the soil. Don’t dig those leaves in, don’t rototill things. What you want is you want the organic matter layered on the surface, the soil life and the microbes will do the job of bringing it down into the soil and breaking it down. And what’s wrong with tilling? If you till it up, you’ll accelerate the decay process it’ll expose it to oxygen, you’ll burn it up. And what you’re wanting to do is put that organic matter in the biological bank. You want it to increase your organic matter account. So, you layer it on the surface, let it naturally start to rot. It’s great to bring compost into play. We compost our food scraps. Anne has a worm bin in the back and it actually introduced beneficial microbes as well. A really great source is to use the worm compost as sort of a root stock, if you will, for brewing up a compost tea. Which is, if you take a five-gallon bucket and get an aerator like you would have in a home aquarium and you add a source an inoculate of microbes, like some of your worm compost from the worm bed and then add a source of sugar, like molasses for example to that to feed microbes. Then what you’re doing is home-brewed microbes. You’re basically brewing up turning probably hundreds of thousands into trillions of microbes and if Anne sprayed those on her plants, on the soil, on the yard, basically trying to inoculate the yard with beneficial microbes which can help keep pests and pathogens at bay and increase the rates of cycling and processing that actually benefit the life of the yard as well. So think about it in terms of trying to restore your soil’s organic matter bank account and microbes that can actually live off that account. Strategies for doing that will be different in different regions but that’s the basic philosophy.
- Tracey:
- Okay. Thank you so much for joining me here today.
- Dave:
- Well, thank you. It was a pleasure talking to you.
