We have just opened the door into a whole new paradigm: the ecology of the atmosphere is driven by microbes and vegetation. That's earth shattering, because everyone said the atmosphere is all about atmospheric physics, dead stuff. We're saying no, it's microbiology that drives so much of the climate.

I just listened to a mind-blowing podcast episode: Rebuilding the Soil Carbon Sponge and Cooling the Climate Fast with Walter Jehne. It is from the Regenerative Agriculture podcast, where farmer John Kempf interviews Dr. Walter Jehne, an Australian soil microbiologist. It's from 2019, so I'm a little late to the party, but I am so excited that I have to share.

I've always been interested in the idea of regenerative agriculture, but when I would try and read about the practices that are associated with it: diversifying crop rotations, planting cover crops, retaining crop residues, reducing tillage frequency and depth, eliminating synthetic chemicals, etc.¹, my eyes would kind of glaze over because I didn't really have the context. So this podcast episode may not be as mind-blowing to people already knowledgeable in the field, but I loved it because it ties so much of the underlying mechanisms together to give you a whole-picture paradigm of why these are the practices that work and not just what the practices are.

It also goes to some unexpected places. I had no idea bacteria was involved at all in clouds. This is just the beginning of my understanding, but it's given me a place to start asking the right questions. For this post, I'm basically just going to do my best to transcribe the salient points of the conversation with some links to other resources that go into more detail about things Dr. Jehne mentioned.

The basic idea though, is when we talk about the need for carbon sequestration, it is not just about the CO₂ in the air. That is just a symptom of the underlying problem, which is the imbalance of the Earth's hydrology, and in fact, we should be thinking of CO₂ as a resource in the hydrological system, which is nature's built-in temperature regulator.

Here's the interview:

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John: What led you to start looking at the impacts of water on atmospheric temperatures and considering a different narrative rather than [just considering] CO₂ as the primary greenhouse gas?

Walter: Climatology 101 makes a simple, undeniable point: water governs 95% of the heat dynamics of the blue planet and has done so for the last 4.2 billion years. It's a foundational principle of atmospheric physics and the Earth's climate. The CO₂ greenhouse component, which I must stress, is absolutely real, but it represents less than 4% of the heat dynamics of the blue planet.

Nature has evolved a hydrological balance that has both warmed the planet - it has made it 33 centigrade warmer than it would be if it were just an inert physical body in space in this part of the solar system. The natural greenhouse effect due to water vapor makes it 33 degrees warmer, but it's also our disturbance of 95% of that heat dynamic process that has now caused abnormal warming in the last 250-odd years...

The CO₂ rise is a symptom of our disturbance of the biosystem, from our excess oxidation of carbon from the biosystem, but the actual thing that is driving climate change is that land degradation on the hydrological dynamics of the planet. And so the challenge is not just to draw down the carbon dioxide - or see it as a pollutant - which is just silly. The point is it's our resource, that it is a building block we need to take to rebuild our landscape, our soils, so that we rebuild the hydrology we disturbed, and in rebuilding the hydrology, restabilize the climate, cool the climate, safely and naturally in the next 10 years. If we leave it any longer, it is very, very serious, dangerous, and damaging.

John: How can we cool the climate without reducing CO₂?

Walter: We will have to reduce CO₂ for the simple reason that we have to rebuild the Earth's soil carbon sponge. That's where the bridge between carbon management and hydrology management really hits the ground. That is our unique point of agency. That is what we have destroyed. We have destroyed the soil carbon sponge. In that process, we put CO₂ in the atmosphere, we have aridified, reduced the amount of water available. [Farmers] like CO₂ because you get the fertilizer effect but only if you have soil water. Without water, whatever CO₂ up there is no use whatsover. Without water, there is no life.

We've got to take CO₂ as the actual cement to rebuild healthy soil structures, rebuild the cathedrals, voids, and surfaces in healthy soils. That's where water is able to be infiltrated and retained, and that's where productivity, that's where resilience, comes from.

As far as the extremes that we are facing, we are not going to die from CO₂. We are going to die if we aridify and don't have the water for life or food that we need to produce.

The sponge is critical to buffer the extremes. The sponge allows us to infiltrate water in the soil, to minimize flood peaks, to minimize erosion storm damage, and it's also the source where we can sustain the longevity of green growth, so when there are dry periods, it's only the sponge and the water in our sponges and in-soil reservoirs that allows life to extend over those dry periods.

The sponge is the point of agency in nature, and our only point of agency to rebuffer and stabilize these extremes. It's the extremes that are actually going to destroy us, destroy biosystems, and kill people. Whether they are hurricanes, whether they are floods, whether they are erosion, whether they are aridification, droughts, wildfires. It's these extremes, and they're all hydrological, and they are all prevented through buffering through the sponge.

John: One of the considerations of the carbon soil sponge is not only the capacity to store water, but also the capacity to deliver water to plants when they need it. It's not just soil water-holding capacity, it's also water-release capacity.

Walter: It's the longevity of green growth that governs the whole health of the biosystem and food production. It's the capacity to sustain over time enough water supply from the soil to maintain that crop finishing, that pasture growing. If we have the sponge, and we get to save 1 inch of rain, that water infilitrates and is made available slowly over 100 days. If we concrete that catchment and degrade that sponge, if we have hard compacted soil, it basically runs out of water in 5-10 days or less. It just runs off the roads. So we have 1000% increase in productivity, a ten-fold increase in longevity of green growth from maintaining the sponge.

John: How does improvement in soil water-holding capacity then contribute to a stable and to a cooler climate?

Walter: Every time a tree or plant transpires, it takes water from soil and turns it from a liquid into a gas (water vapor). To do that, every gram of water needs 590 calories of heat energy to make that transformation. It's called the latent heat of vaporization. That heat comes from the surface soil and the surface environment. So every gram, every cubic centimeter of water that is transpired, cools the surface 590 calories of heat energy. There's vast quantities of transpiration taking water up into the air over long periods of time. This is a massive, natural, safe cooling effect. By degrading our landscape, we are limiting that natural air conditioning cooling effect of the planet. Immediately, simply shortening productive green growth results in a warmer surface. Globally, some 25% of the incident solar radiation coming from the sun is naturally transferred from the surface back up into the atmosphere through these transpirational latent heat fluxes.

Nature is buffered and self-regulated. If we cooled it too much, photosynthesis would slow down, transpiration would slow down, and we would be back in natural homeostasis.

There's more parts to it. For example, high albedo reflective clouds reflect up to 1/3 of solar radiation back out to space so heat doesn't even get to the Earth, so a 2% increase in cloudiness would offset abnormal warming.

But if we don't have the sponge, we don't have the water to transpire into the air to form clouds, to drive these cooling processes. If we concrete the catchment, we end up like Mars, and we don't have any of these cooling capabilities.

John: From what I've understood from our conversations in the past, we need the carbon sponge, but we also need the capacity to change the way water behaves in the atmosphere. Water behaves differently today from what it has in the past because of the way we've impacted aerosols and other things in the atmosphere. Can you tell us a little about that?

Walter: Nature has governed the temperature balance of this planet through evolving two very sophisticated opposing processes that either warm the planet or cool the planet. We've talked about the water vapor going up from the trees which cools the surface, but that water when it then goes into the atmosphere condenses and releases that energy, a lot of which transmits back out into space, but then forms haze micro-droplets. We see this as mists and hazes in the air. Haze is billions/trillions of these micro-droplets. To form a micro-droplet, water has to condense onto some aerosol particle. Nature (and this is James Lovelock's work in the 1960s) produces a lot of these aerosols from plants and vegetations - the dimethyl sulfide from marine algae, the isoprenes from forests, the pinenes, terpenes again from forests - so nature is producing a lot of these aerosols and they actually create the hazes and provide a natural warming effect in the atmosphere.

But what's happened is that we have massively increased the amount of aerosols that are now in the atmosophere. We have created 5 billion hectares of man-made desert and wasteland on this planet. There's only 14 billion hectares of land in total, so 40% of the land surface is now desert and wasteland which produces some 4-5 billion tons of dust particles that enter the air every year. These are acting as haze particulates. Every year, we burn 400 million hectares of forests and some 2 billion hectares of grassland on this planet, and of course the carbon particulates from that fire are going into the atmosphere and increasing haze. Every year we burn 8 billion tons of fossil fuels, and again a whole lot of carbon particulates and polyaromatic hydrocarbons enter the air. So we have created a massive increase in this aerosol release, and as a consequence, increasing the level and density of these humid hazes and their warming effect. We have a pollutant brown haze that now stretches from Cairo to Beijing.

These humid hazes heat an area, for example in the Middle East, the Persian Gulf, in the summer, it's 50℃ (122℉) temperature, 95% relative humidity, well exceeding the capacity for mammals, including humans, to survive, because we can't perspire, we can't cool ourselves, so this is a dangerous heat impact.

So that's the heating component. And nature, to balance that, has actually evolved an even more exquisite process. And these are the hygroscopic precipitation nuclei. Nature puts molecules in the air which absorb and coalesce a million of these haze droplets to make a cloud droplet. It can coalesce hazes into dense high albedo clouds, and these clouds reflect sunlight and cool the planet. So through this simple matter of coalescing hazes into clouds, nature can switch it from a warming to a cooling process. And it is through this balance of these microbial hygroscopic nuclei that nature has regulated the temperature of the atmosphere.

There are three components that cause this hygroscopic removal of hazes into cooling clouds. And they are: ice crystals, which are critically important at high altitudes, latitudes, and cold fronts. Over the ocean, we've got salt, sodium chloride, which creates most of the clouds over the oceans. But the most important precipitation nuclei that is produced in nature and drives over half the rainfall and cloud formation, particularly in the tropics and inland areas, are bacteria. Bacteria produced in the stomatal cavity of certain trees which then go up into the air as part of the transpiration stream, nucleate these hazes, form dense clouds and then rain, and basically drive the whole hydrological cycle.

It's one thing to put water vapor or hazes into the air, but of course nature has had to evolve a way to bring it back down as clouds and then rain because only then does it have regulation.

So these hygroscopic bacterial precipitation nuclei are produced by certain forests. And by destroying those forests, we have a massive effect. We've got lots and lots of hard evidence whereby forest destruction has now crashed rainfall in regions even though there is other vegetation there. Remove the forests, you lose the rainfall, you aridify those regions.

Rebuilding this balance between haze formation through aerosols and the removal by precipitation nuclei is a fundamental balance that we have to restore.

John: What is missing to restore that balance?

Walter: We want to reduce the hazes. And here are the really practical, very rapid ways that we can and must do this. The first thing is maintain soil cover. We maintain vegetation, protective cover on soil as nature had. Because it's basically when we have bare, exposed soil to heat, to wind, that we get dust, and we can reduce that on the planet. The more ground cover, the more ground insulation, we can do that practically everywhere. Secondly, we can stop these massive fires. They put up more carbon dioxide in the air than fossil fuels. We can massively limit the carbon particulates in the air. And obviously, we've got to keep on trying to reduce fossil fuel use and the polyaromatic hydrocarbons coming from there.

On the other side of the equation, we can't change ice crystal formation readily. We can play around with putting salts in the air as we do with cloud seeding with silver iodide, but again, very expensive and hubristic in a way, and very limited in scale. But what we can do is, we can say, how do we restore these natural forests that produce up to a billion tons of bacteria - protoplasm pumped in that go into the air every year. We used to have 8 billion hectares of primary forest 10,000 years ago. We have cut 6.3 billion hectares of that forest, some of it has regenerated, so now we have 3.5 billion hectares of forest. Basically, we have massively disturbed and reduced the amount of these hygroscopic precipitation nuclei. We've changed the cloud formation capacity. And more seriously, we've changed the rainfall induction. Over half of the rainfall on this planet is driven by these hygroscopic bacterial nuclei effectively in a symbiotic process. We all know that trees and plants need rain. But now, we know rain needs trees.

We have just opened the door into a whole new paradigm: the ecology of the atmosphere is driven by microbes and vegetation. That's earth shattering, because everyone said the atmosphere is all about atmospheric physics, dead stuff. We're saying no, it's microbiology that drives so much of the climate.

John: There's a lot of anecdotal evidence on smaller scales - I'm thinking of Las Gaviotas in Colombia and other stories of regenerative farms that have significantly changed rainfall in the local environment with relatively small amount of trees, a few sq km or less, in many cases quite a bit less.

Walter: Please, please don't say this is not hard evidence. That's nature. That's reality. Don't let anyone bluff you that that isn't evidence.

Nothing is more solid as evidence as nature. Just because it's not in somebody's computer model, don't ever doubt nature. Back nature, because that is reality. What you just said there is actually the proof. That's really where the evidence is. It's not in somebody's assumptions. It's in a sense the problem we got. Conventional science says not proven, not proven. No sorry, reality has been proven. Reality is reality.

John: I think we collectively have enough experience that even while the evidence may not yet all have been quantified and published in the peer-reviewed literature, we are in a situation where we need to take the experience that we already have and apply it. We can't afford to take another 10 or 20 years to first quantify it and first validate it. We need to begin immediately with what we already know.

Walter: Let me just say: it is validated. There is nature. You are standing in it. You don't need some computer model to guess at it. If you have people who have documented, yes, we have reforested this area, we have had these hydrological effects, that is reality, that is the evidence. I am just so passionate about backing reality, backing the innovators in the field, because that is the frontline of knowledge, understanding, and actually saving this planet.

John: I was going to ask you how you are using trees in Australia. Are they being planted in shelter belts? Are they being scattered across the landscape? What do you find to be the most effective?

Walter: Very important question. Basically, we've got recognition now globally and people are talking about "let's plant a billion trees." Give them 100 marks for aspirations and 5 marks for reality. Because planting a tree unless it's got water and the right soil environment... the probablity that it's going to be dead in 3-4 weeks... We've got to rebuild the sponge, the hydrology, because only then will planted trees survive. But let's flip it around. If we rebuild the sponge and the hydrology, then mostly trees will naturally regenerate from seed from adjacent areas.

We can regenerate vast areas of degraded, arid areas not by planting trees, but just by rebuilding the sponge, and then allowing natural successional regeneration of trees and grasses and shrubs to move into that area. If there is water there, life will follow, sure as eggs², no question.

That becomes the issue. How do we not just look at where we are above the surface and say "hey we want this tree" because that's what we can see. It's actually respecting what's down under, what's in the soils, the hydrology, the nutrition, the microbial diversity, because once we have that, trees come automatically.

John: Of course in order for that to happen, that means that we cannot have sterile fence rows. It means we cannot have borders between our fields. And we need to discontinue this ideal of having a completely clean field, and clean field borders constantly being sprayed with herbicides.

Walter: In Australia, because we are a bit drier, we are going to a whole new paradigm for agriculture.. we've got concepts like nomadism. We've imprisoned ourselves in the 19th-20th century in these fence lines. "We've got four pegs, this is our land." We've tried to over-exploit that land until we die. We mostly will die if we stay there. We've got to change that. This whole concept of fences may have to go. This nomadism, this new concept of agriculture where we opportunistically pasture crop where the seasons are. So with us, we are going right back to the wisdom of first nations people. They worked in the ecology of these systems, and we have to respect and look at how we apply that wisdom particularly in an aridifing climate like Australia. But I agree. The idea of fence lines and spraying and killing. No no, we've got to foster life. We've got to foster diversity and flexibility.

John: [Any last thoughts before we go?]

Walter: Simple take-home message: the sponge, the sponge. Take the carbon and build the sponge. It's as simple as maximizing photosynthesis, maximizing plant growth as best you can. Minimizing oxidative inputs. Excessive cultivation, excess fertilizers, the biocides. Understanding organic debris is turned into humates and glomalin by soil microbes. Let nature and microbes build that soil carbon sponge for us.

The other key point is the nutritional integrity of the food we are growing depends again on the sponge and the nutrient availability in all those soil surfaces created in the sponge. We have massively compromised the nutritional integrity of the food we now eat and our preventative health has crashed because of that. We have got exponential increases in all sorts of diet-induced diseases, totally unsustainable, and so down the track, it will actually be consumers that will be demanding healthy food with healthy soils to keep people healthy. And in a sense, that is the forefront of the paradigm change, the tipping point, and actually our only way to feed and look after and maintain stable communities into the future.

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Some caveats: I haven't found another reference for "half the rainfall" being attributed to the bacterial precipitation nuclei. Dr. Jehne also notes that this is still frontier stuff. A lot of the data is probably still being corroborated. If I had commenting capability on this blog, people with more knowledge could link more sources in the comments, but as I don't have that yet, send me a LinkedIn message please! At some point, I think I will add Remark42 to this site...