Dirty Secrets: What We Can Learn from Soils


What goes on in the secret lives of soils? While people passing by are brushing off the dirt from their shoes, what is being brushed off with it? One of the most fundamental resources on our earth is under our feet with every step, and we so rarely look down.

Soils are the basis of life on land. Nearly one quarter of all species on Earth live in soils. Most of these organisms are too small to see with the living eye – if counted, there would be more microorganisms in one gram of healthy soils than there are people on Earth. However, only one percent of these soil microorganism species have been identified (source). Given the vast knowledge we have already gained from soils, scientists eagerly await the promise offered by this mysterious 99% of soil life. But the question of “what can soils do for us” is limited and too utilitarian. Instead, let’s ask “what can soils teach us”, because we have a lot to learn.

Wise words, and inspiration for this blog, from @yaminapressler on Twitter

Relationships with early life

Soil’s secrets began billions of years ago. As the first living things adapted to move from water to land, soils were the silent partners in the wonder of evolution. The evolution of early photosynthetic life, like stromatolites, contributed to the formation of soils rich in nutrients and organic matter. Soils can reveal new information about this early life: frozen soil unearthed in a receding iceberg in Greenland hints at the existence of photosynthetic microbes 2 billion years earlier than we had previously thought (3.7 billion years ago, as opposed to 3.5 billion).

As life continued to evolve, evidence was captured in soil fossils, called paleosols. These fossils are evidence for mutualistic, beneficial relationships between soil and plants. Plants helped break down rock for nutrients and create soil structure. In turn, soils returned these nutrients to plants and provided water, oxygen, and support. Forget secret celebrity romances; the relationship between plants and soils is what we need to be talking about.

Learn more from my blog for the Canadian Society of Soil Science: How did the first soils evolve?

Filtering dirty water…with dirt

Believe it or not, soil is one of the best water filters out there. As water seeps deeper into the ground, infiltrating the soil, different size particles, like sand or clay, physically filter out contaminants. Most soils also have a slight chemical charge which attracts and captures chemicals (like ammonium) with the opposite charge. The soil keeps the pollutants as the water passes through. Furthermore, soil life, such as bacteria, may use the pollutant and transform it into something less harmful. This process of bioremediation can be used to clean up oil spills. For example, in the Deepwater Horizon Oil spill, microbes like  Alcanivorax borkumensis were used because they naturally remove oil hydrocarbons to use as energy. Learning from soil, many treatment facilities use the same physical, chemical, and biological processes that soil does to filter water.

I love doing this at-home experiment building your own water fiilter! This image comes from https://www.ealt.ca/kids-blog/water-filtration

Soil civil war and antibiotics

Soil microorganisms aren’t necessarily at peace – they are constantly battling each other for survival, space, and resources. Fungi, bacteria, and other critters are engaged in an ongoing soil civil war. However, once we discovered this war, humans were able to harness the microorganism’s weapons: antibiotics. Antibiotics are chemical compounds that inhibit the growth of or destroy microorganisms and are often produced by different microorganisms as a weapon. Today, antibiotics are one of the most common classes of medicinal drugs and most of these antibiotics came from soil (source).

Even as we increasingly see diseases evolve to be stronger than antibiotics, called antibiotic resistance, soil may still hold the answers. In 2014, researchers engaged in the fight against antibiotic resistance found that a compound naturally produced by a fungus inactivates one antibiotic resistance gene, once again making the bacteria vulnerable to antibiotics. If we are going to fight against microbes, we don’t have to do it alone: soil microbes have been fighting against each other since the beginning.

Climate change superpowers

Soil has even more secret superpowers that urgently need to be discussed: the power of carbon sequestration. Carbon sequestration is the process of capturing and storing atmospheric carbon. Plants remove carbon dioxide from the atmosphere and store it in soil as organic carbon. Soil is particularly good at storing carbon: Earth’s soils store about 2,500 gigatons of carbon, almost 3 times more than that found in the atmosphere.

All of this matters because atmospheric carbon, like carbon dioxide and methane, are greenhouse gases causing climate change. Soil carbon sequestration is a relatively natural way of removing greenhouse gases from the atmosphere with fewer impacts on land and water, less need for energy, and lower costs. Soils remove about 25% of the world’s fossil fuel emissions each year. However, soils are losing carbon – thawing of frozen permafrost, agricultural practices, deforestation, and draining of the peatlands have led to soil losing 50 to 70 percent of the carbon they once held (source). This is why much of soil science research focus on how carbon moves into and out of soil.

A cool interview I did with a soil scientist about the role of agriculture systems in greenhouse gas emissions

So, look down. Pay attention. Appreciate the world beneath your feet. Since the beginning, everything on Earth relates back to soil. From growing food to preventing erosion, and from antibiotics to climate change, soil is the behind-the-scenes hero supporting Earth as we know it. Soil can teach us more than we know to ask about. It shouldn’t be a secret how important soil is – let’s talk about the dirt on soils.

What did I miss? A lot. Check out this infographic from the Food and Agriculture Organization of the United Nations on all that soil can teach us, and follow the Canadian Society of Soil Science on Twitter for more #SoilScience (@CSSS_Soils).