Soils are more than just a medium for plant growth
Studying soils is not just a scientific endeavor. It is an exploration into nature, culture, and life.
What comes to mind when you think of “soil”? You might respond something like this:
Soil is a habitat for plants
Soil is the stuff in which plants grow
Soil is the foundation of agriculture
And you would be right — soil is, indeed, a habitat for plants. Soil is, in fact, the basis of all agriculture.
Much of our connection to soil is through the lens of agriculture. When I tell people I am a soil scientist, they most often respond with a question of how they can improve their garden. This simple question, while well intentioned, reminds me that many people see soil as secondary to plants. Our culture has framed soil as a tool we can manipulate to grow food. And while this may be true,
soil is so much more than that
Soil is more than just a medium for plant growth. Soil is a complex, interconnected system that underlies all of your favorite landscapes. Soil is full of life and biodiversity — more than that of a tropical rainforest. Soil is dynamic and responsive to our actions as humans. Soil is creative and destructive. Soil is fundamental to everything we do.
Soil scientists have lamented the notion that soil is nothing more than the stuff in which plants grow for decades:
“Many ecologists glibly designate soil as the abiotic environment of plants, a phrase that gives me the creeps” — Hans Jenny
As a soil scientist myself, I am no different. While the fact that soil is the habitat that supports plant growth is undeniable, this is a superficial view of what soils are and how they function. If you look closely, you’ll learn that soils are complex, nuanced systems that we are still so far from truly understanding.
Humans have been deeply connected to soils throughout our existence. Yet, modern life has slowly removed many of us from our day to day experience with soils and this deep connection has turned shallow. Soil has fallen out of our public consciousness.
Soils are the foundation of all ecosystems
Soils are not just important in agriculture. Soils underlie all ecosystems, even aquatic ones (shout out to subaqueous soils!). Soils are the foundation of forests, deserts, grasslands, tundras, lakes, and even urban ecosystems.
That beautiful old growth forest you went to visit in Olympic National Park last summer? Grounded in soils.
The wide open savannas of West Texas you enjoyed on your drive out east? Wouldn’t be there without soil.
The local trail through the woods you mountain biked the other day? Follows a path of soil.
The scenic drive through your favorite national park? Cut through soil.
The dog park you spend every Wednesday afternoon at? Needs soil.
Your favorite beach on the coast of Cancun? Soil.
You get my point: soil is ubiquitous. It’s everywhere. It’s undeniable.
But somehow we have forgotten. Forgotten that underneath every concrete slab and asphalt street is soil. Forgotten that the trails we hike on Saturday mornings are carved on soil. Forgotten that soil is more than just the stuff we fill our planter boxes with.
Soil is living natural body worthy of study
Soils in an of themselves are their own ecosystems. Soils harbor a perplexing amount of biodiversity from microorganisms (bacteria, fungi, and archaea) to mesofauna (tardigrades, nematodes, mites) to macrofauna (earthworms, millipedes, beetles). Soils are an endless frontier of biological discovery.
But why? Why are soils so biodiverse?
Soil scientists have contemplated several reasons. For one, soils are a mix of different materials. These materials include minerals, organic matter, plant material, dead organismal biomass… the list goes on. These materials serve as the sustenance for soil organisms. Diverse foods yields diverse biological communities.
Another reason is scale. Soil microorganisms operate on a micron scale. They are tiny and inhabit every little pocket of soil. Compared to aboveground ecosystems, there’s simply just more habitat space to fill up belowground. There are more crevices of soil for organisms to exploit. There’s more room for evolution to drive the differentiation of new species.
Soil microorganisms also have the benefit of a long evolutionary history. They have been evolving hundreds of millions of years longer then mammals and humans. Their generation times are also much shorter than mammals, so the process of evolution simply happens faster.
Soil conditions fluctuate regularly — water comes and goes, pH changes, food sources shift, temperatures waver. It’s not always an easy place for many organisms to survive. Soil microorganisms often go dormant when conditions are unfavorable, and simply wait it out. If they didn’t have the ability to go dormant, biodiversity would be lost as soil conditions fluctuate outside optimal ranges.
And sure, biodiversity belowground depends on plants to provide litter and organic matter — but the microorganisms don’t “care” what the plants are up to. They are simply responding to stimuli and signals from the environment.
When you look at it this way, soils become so much more than just a place in which to grow plants. Soils are full of interacting organisms. Organisms interacting with each other; organisms interacting with their environment. If that isn’t an entity worth of study, then the whole field of ecology may be moot.
Soils form our cultural identity
If you grew up in the midwest, you’re likely familiar with what comes to mind when most people think of soil. Thick, dark brown, organic matter rich soils that boast some of the most productive agriculture in the world. If you’re from the southwest, sandy, red soil may be what you are familiar with. If you grew up in the south, marshy, wetland soils may be your jam.
Your perception of soil is probably closely intertwined with where you spent your formative years. Whether you realize it or not, your cultural identity is tied to soils.
Even something as simple as soil color can be illuminating to the diversity of soils themselves (not just the organisms that inhabit them). Soils can be just about any color under the sun. Soils are not just the dark brown classic agricultural soils you might be picturing. Soils are red, gray, pink, yellow, blue, white, black. Soils are a rainbow belowground.
And once you realize this diversity of soils, you’ll see that humans cultures have been shaped by the properties of their soil for as far back as we can remember.
Greek, Roman and Aztec empires all had sophisticated soil knowledge. They classified soils by their properties (color, structure, texture, rockiness) and their ability to grow certain crops. Depictions of soils in cultural artifacts go way back. Soils were used in spiritual and religious ceremonies as pigments for paint. Soils were seen as an important resource that could be damaged by human activity and poor management. Societies with productive soils and responsible management practices thrived. For those that didn’t, well, you know how the story ends.
It is clear that our predecessors had a strong connection to soils. Where has this connection gone?
As soon as we elevate soil above it’s current position as simply the medium for plant growth, we will see we still have so much more to learn. In soils, you can learn physics, chemistry, biology, ecology, medicine, anthropology, and geology. Soils encompass all of science. In soils, you can connect to culture, society, and our fundamental values. Soils encompass all of society.
From soil comes all life. We can all be better connected to our soils.
