By Raechel Hearth, C2ST Intern, University of Chicago

You always hear people say “look ahead” or “hold your head high,” but I would challenge you to take a moment to look down and think about the ground below. When I was little – much to my parents’ dismay – my favorite pastime was finding the muddiest puddle around and splashing away in it! If it wasn’t that, I was taking my toys outside and building entire ecosystems for them in the ground, including caves, mountains out of dirt, or even whole river systems using a hose. But this material is more than just a fun mess! Below us is one of the Earth’s greatest resources: soil. It is teeming with life, full of structure, and yet remains mostly hidden to us. In this blog, I hope to share just some of the many ways that soil is unique, fascinating, and crucial to life on Earth.

First, what is soil? Believe it or not, even this is a complicated question. Many scientists have put forth definitions of what soil is, ranging from a solely materials and minerals focus to viewing soil as a dynamic, living system. Most definitions are multiple sentences long as they try to describe this complex and wonderful resource. For now, let’s just agree that soil is not just dirt; it consists of a combination of minerals, gases, water, organic material, and living organisms. But don’t worry too much about exact definitions! Let’s instead focus on what soil does; specifically, how does soil help to promote life on Earth?

Soil supports plant and animal life and provides growth for 95% of the food humans consume. In fact, it is often the various properties of a soil that determine the type of vegetation that can grow in it. Thus, soil impacts the type of overall environment and other forms of life such as animals, including humans, that can live there. Another important feature of soil is its ability to cycle and recycle various materials. Much of the Earth’s fresh water from lakes, rivers, streams, and aquifers runs through soil at some point. Soil acts like a filtration system for this water. As water travels through soil, it can remove impurities and certain pathogens. Soil also acts as a home for a huge amount of Earth’s life, with microbes, insects, and larger animals living in soils around the world. Estimates say that even just a handful of soil could contain billions of potential organisms. Additionally, people around the globe use raw materials from the soil – like clay – for construction purposes, as well as relying on soil structure to build on for the majority of human infrastructure. Soil acts as a base for our cities, roads, and houses. One surprising and lesser-known use of soil is as a consumable product. There is a history of eating soil among a wide range of cultures for millions of years. For example, the Luo people in Kenya eat soil during pregnancy because they believe there is a connection between soil, blood, and fertility. These are just a few of the many ways in which soil impacts our lives!

Soil not only has a variety of uses, but also lots of individual variability. There are twelve unique soil orders, each characterised by properties involved in the formation of the soil. Often these orders vary in mineral composition, pH, amount of organic matter, and erosion and drainage capabilities, just to name a few! Chicago is dominated primarily by two soil orders: Alfisols and Mollisols. Alfisols are primarily characterised as forest soils, while Mollisols are a common type of grassland soil. This makes sense, as historically Chicago was covered by prairies, wetlands, and forests. Chicago is also home to Entisols, which are soils that have very little development and no distinctive layers. Often, this type of soil is found on steep slopes or areas with recent lava flows, where a new soil profile is just beginning. However, Entisols in Chicago lack distinctive soil layers due to the large amount of industrialization and construction present in the city. Many scientists have suggested adding a new soil order to characterize these heavily disturbed, urban soils as separate from other Entisols. But for now, they remain classified within this extremely diverse soil order. The USDA is a great resource if you want to learn more about the ins and outs of each of the twelve global soil orders. 

I’d like to end by considering what threatens soil health globally and how we can better promote the health and stability of this amazing resource. The majority of the threats to soil health are human-caused. Some estimates say that up to a third of our soil is already degraded. Soils are often the product of thousands of years of formation, making it hard for this resource to rebuild if human activity destroys it. Threats such as erosion, pollutants, compaction, and nutrient depletion are just a few of the many threats to soil security. On a larger scale, we need to think about managing soil sustainably. This means using it in a way that provides us with what we need now without jeopardizing soil productivity in the future. Although larger-scale human activities – like agricultural practices and industrialization – are hard for one individual to combat, there are small things that we can do. I think a great place to start is to learn more about the importance of soil and to tell others! Get neighbors involved in planting more native plants, embracing more natural lawns, or eliminating harsh chemical use. Public opinion and community involvement can go a long way to making a difference! Through actions and words, people can prove that soil is not just dirt, dust, or grime to be washed away, but a wonderful resource that keeps us all alive.

 

References (outside hyperlinks): 

Brady, N. C., Weil, R. R., & Weil, R. R. (2008). The nature and properties of soils (Vol. 13, pp. 662-710). Upper Saddle River, NJ: Prentice Hall.

McBratney, A. B., & Hartemink, A. E. (2024). Define soil. Soil Security, 14, 100135.