What is Healthy Soil?
The mind bending truths about soil health and our role as stewards
When I talk about soil systems I’m careful to indicate that it's *healthy* soil which provides so many services to the greater environment. But that begs the question, what IS healthy soil? Today, at the start of a fresh new year, let’s get back to basics, to the essence of what it is we’re seeking to take part in.
Understanding Ecosystems
Healthy soil is characterized by the living ecosystem belowground and the emergent properties of soil life interactions. To understand how life in a soil ecosystem works, we can first think about an aboveground ecosystem. For instance, consider a food web, like this one:
When I look at any food web diagram I see 2 key things:
Energy Transfer: as a predator eats prey, nutrients and energy are being transferred / cycled through the ecosystem
Checks & Balances: predation keeps prey populations in check which allows for a diverse and stable ecosystem
As you can imagine, if a key predator is wiped out from an ecosystem, their prey populations will be allowed to rapidly increase which initiates an undesirable domino effect - the prey may decimate certain vegetation they feed on, which in turn affects other plant and animal species who rely on that vegetation and so on.
A classic example of this is the decimation and then reintroduction of the wolf population in and around Yellowstone National Park. These excerpts by a piece published in The Guardian written by Cassidy Randall capture the effects:
The need for restoration was glaring. In the 70 years of the wolves’ absence, the entire Yellowstone ecosystem had fallen out of balance. Coyotes ran rampant, and the elk population exploded, overgrazing willows and aspens. Without those trees, songbirds began to decline, beavers could no longer build their dams and riverbanks started to erode. Without beaver dams and the shade from trees and other plants, water temperatures were too high for cold-water fish.
Scientists always knew that as the top predator, wolves were the missing piece in this ecosystem. But they were astonished at how quickly their return stimulated a transformation. The elk and deer populations started responding immediately. Within about 10 years, willows rebounded. In 20, the aspen began flourishing. Riverbanks stabilized. Songbirds returned as did beavers, eagles, foxes and badgers. “And those are just the things we have the time and funding to study,” said Smith. “There are probably myriad other effects just waiting to be discovered.”
What may be harder to imagine is that these same predator-prey dynamics, and the cascading effects of them, occur in the ecosystem belowground 👇
Soil Life
The main prey groups in the soil food web are bacteria and fungi. And, to keep it simple, a group of organisms called protozoa and another, nematodes, are the main predators (at least at the microscopic level 🔬, upon which higher trophic levels depend).
Nutrients cycle to plants via predator-prey interactions in the soil
When a protozoa consumes bacteria, they take the nutrients they need and excrete what they don’t in the form of PLANT AVAILABLE NUTRIENTS! It is through such soil life interactions that plants have received the nutrients they’ve needed for millennia before the advent of fertilizers. Nutrient cycling is just one of many emergent properties or ecosystem services provided by a dynamic living soil.
Here’s the problem: what we typically see in soils that have been developed or cultivated is a lack of biodiversity - there are little to no predators, and a significant lack of fungi (a prey group).
Why might that be? What happened to the predators?
Ecological Disturbance
Common disturbances like leaving ground bare, compaction, synthetic fertilizers, herbicides, and pesticides tend to kill most of the microscopic soil life we’re discussing, with the exception of some types of bacteria which, in the absence of predators, tend to bloom under such disruptions.
If only bacterial blooms were pigmented like algal blooms - the stories they’d tell!
I like to think of ecological disturbances in 2 categories - overt and covert, or obvious and hidden. Overt disturbances clearly decimate vegetation so it’s no surprise the soil ecosystem is just as affected by such events. However, covert disturbances tend to affect the soil ecosystem first - a place less perceptible to the human eye - therefore it’s more difficult for us to connect the dots between a source of disturbance(s) and the effect it’s having on soil and plant health. I believe this is why we tend to participate in covert disturbances frequently and over long periods of time, because their effects, though often just as disruptive, aren't as plain to see as a landscape that’s been torched.
EXAMPLES
Overt Disturbances: excavation, wildfire, floods, overgrazing, heavy tillage, avalanches, volcanic eruptions!
Covert Disturbances: synthetic fertilizers, herbicides, pesticides, bare ground, compaction, “light” tilling, toxic runoff
Ecological Succession
Another shared principle of ecosystems, be it aboveground or belowground, is the concept of ecological succession. The diagram below may be a familiar concept; it illustrates the theory of a natural progression of a landscape’s vegetation - from a barren landscape to an old-growth forest - as each stage of plant succession prepares the land for the next type of vegetation.
We’ve understood succession from a landscape perspective for centuries (if not longer, before these things were recorded), but what’s been discovered more recently is the succession taking place belowground - there are soil ecosystem characteristics associated with each stage of plant succession. This is incredibly useful insight!
When we hold space in our mind’s eye for these two ecosystems that are connected to one another we can see how we’re often trying to grow mid to late succession plants on disturbed, early succession soils. This mismatch results in “needy” plants that may experience deficiencies or diseases. When plants die back, this is nature’s process of creating different conditions in the soil that will support the next stage of plant succession (albeit on a timescale that humans don’t have much patience for, after all we need food now - those needs matter too of course).
Our Role
When we observe a needy plant we tend to, with good intention, try to keep it alive (for its sake and ours) by responding with fertilizers and pesticides which, as covert disturbances, keep the soil food web imbalanced, in a state of bacterial blooms with little to no predators. We’re actively, though inadvertently, maintaining mismatched conditions between the soil and the plants we desire.
Due to the limitations of the human perspective we can’t see the effects our practices are really having on the soil ecosystem, so we continue with these practices and they never improve soil health, they destroy it, keeping us bound to constant inputs and longing for things to change for the better.
Our Longing
And boy do we long, we long for beauty and abundance, we long for health and vitality, we long for connection with our surroundings - to know and be known. So, how do we restore function and health to our soils?
We regard the soil as a habitat, one that we depend on. We regard ourselves as a humble steward, one who earnestly seeks to co-create with other life.
And when we’re feeling less romantic… when connection is hard to find or when the fear on the other side of our longing speaks, we respond with rationale - soil health principles, ecosystem dynamics. We remind ourselves of these truths and gently nudge ourselves away from perspectives we’ve been conditioned to uphold and towards the perspectives that are being shaped by our most honest experiences with our environment.
So there it is, a post to set the tone for the year, one filled with both science and soul because that’s just who I am / who I’m becoming 🤎 The message at the end is something I’ll need to be reminded of myself when I inevitably step into a controlling headspace as I navigate the cultural divide between suburban norms and my inner wisdom. I hope you share this with a friend or leave a comment if you feel inclined. As always, thank you for reading. 💫
Soil (as opposed to dirt) is sexy. Love the name and content of your "newsletter". I am kindred soul, though I came to soil via roots. Please keep the soil science coming! I look forward to reading more.
Thank you! I always love to see others in this space that merge the discourses of science and deep ecology. Makes me feel like I'm not the only one suspended between these two worlds.