# Soils in our cities *one thing about soil* # Human impacts to soils are immense and ubiquitous We humans have manipulated soils to such an extent, that scientists consider humans as a soil forming factor alongside the other major drivers of soil development (climate, organisms, topography, parent material, and time). Why do we designate ourselves as separate from other organisms that influence soil formation? We see the impacts of our activities as even more intense across even grander spatial and temporal scales than other species. Putting ourselves "above" other species, even when it comes to our ability to degrade the environment, is, perhaps, something only humans would do. We also indirectly influence soil formation by altering the climate, determining which plants grow where (both intentionally through agriculture, and unintentionally through the introduction of invasive species) and reconstructing the topography of landscapes to manage crops and water movement. Widespread urbanization and agricultural development has led to the loss of unique, endemic soil types that contribute to a region's "pedodiversity" (the diversity of soil types in an area)[^amundson]. Somewhat ironically, humans simultaneously decrease pedodiversity and threaten rare soils on regional scales[^amundson], while also increasing pedodiversity within cities through the formation of novel urban soils[^pindral]. ![[morro bay embarcadero soil .jpg]] *Soil profile at a construction site in Morro Bay, CA. This site now hosts a new building and pocket park with kids play structures.* # The soils in our cities have unique features Urban soils are those dominated by human artifacts and materials that have been moved by human activities[^nrcs]. They occur not just in cities, but also in suburban areas, industrial regions, and military settings. Because they have been moved and manipulated, urban soils tend to look and feel quite different than their natural soil counterparts[^riddle]. Urban soils are often compacted when material is moved from one place to another, mixed and compressed to create level surfaces upon which to build, and sealed underneath concrete. This limits how well water soaks into the soil and changes the way water moves within urbanized landscapes. All that concrete can also change the chemistry of the soil by making the soil more basic[^riddle]. Modern activities in cityscapes also introduce contaminants, like heavy metals and organic pollutants, that get concentrated in the soil[^riddle]. In landscaped areas between concrete surfaces, organic carbon can accumulate in the surface soil from purposeful organic amendments like compost or mulch and extra irrigation that promotes plant inputs[^riddle]. # Even though urban soils are degraded, they can still provide ecosystem services Urban soils can still provide many ecosystem services that humans rely on[^pindral]. Your local community garden supports food production. Your neighborhood park provides recreation opportunities and wildlife habitat. A reconstructed wetland mitigates the risk of flood. The microorganisms inhabiting soils in human-dominated landscapes quite literally support human health by suppressing soil-borne diseases and regulating air and water quality[^wall]. All that said, the more degraded an urban soil, the less capacity it has to provide these important ecological functions. Soils with at least some vegetation will fare better than soils in dumping sites or sealed beneath pavement[^morel]. In urban greenspaces worldwide, researchers have found that the greater the soil biodiversity, the more ecosystem functions that greenspace will provide[^fan]. We can restore urban soils one patch at a time by making space for sidewalk trees, community gardens, green roofs, and rain garden in parking lots[^byrne]. Stewarding urban soils is both possible and necessary. # Take home message The soils in our cities are unique, important, and worth paying more attention to. Urbanization and agriculture have both led to widespread soil degradation, the loss of unique soil types, and hindered many ecosystem services. In cities, human activities are creating novel soil types that scientists are actively working to characterize. We need to prioritize both conservation of rare soil types and stewardship of novel urban soils. #### Postscript > This essay is part of [[One thing about soil - an educational series]] created by Dr. Yamina Pressler. The essay was originally shared to my [newsletter](https://buttondown.email/wonderofsoil) subscribers. I developed this essay based on a talk I gave a few years back. For more on urban and anthropogenic soils, check out my notes: [[Exploring the formation and function of anthropogenic soils]] *created March 21, 2025* [^wall]:Wall, D. H., Nielsen, U. N., & Six, J. (2015). Soil biodiversity and human health. _Nature_, _528_ (7580), 69-76. https://www.nature.com/articles/nature15744 [^morel]:Morel, J. L., Chenu, C., & Lorenz, K. (2015). Ecosystem services provided by soils of urban, industrial, traffic, mining, and military areas (SUITMAs). _Journal of soils and sediments_, _15_, 1659-1666. https://link.springer.com/article/10.1007/s11368-014-0926-0 [^riddle]:Riddle, R. L., Siebecker, M. G., Weindorf, D. C., Shaw, R. K., & Scharenbroch, B. C. (2022). Soils in urban and built environments: Pedogenic processes, characteristics, mapping, and classification. _Advances in Agronomy_, _173_, 227-255. [^pindral]: Pindral, S., Kot, R., & Hulisz, P. (2022). The influence of city development on urban pedodiversity. _Scientific Reports_, _12_(1), 6009. [^fan]: Fan, K., Chu, H., Eldridge, D. J., Gaitan, J. J., Liu, Y. R., Sokoya, B., ... & Delgado-Baquerizo, M. (2023). Soil biodiversity supports the delivery of multiple ecosystem functions in urban greenspaces. _Nature Ecology & Evolution_, _7_(1), 113-126. https://www.nature.com/articles/s41559-022-01935-4 [^byrne]:Byrne, L. B. (2021). Socioecological soil restoration in urban cultural landscapes. In _Soils and Landscape Restoration_ (pp. 373-410). Academic Press. [^amundson]: Amundson, R., Guo, Y., & Gong, P. (2003). Soil diversity and land use in the United States. _Ecosystems_, _6_, 470-482. [^nrcs]: The USDA Natural Resource Conservation Service conducts urban soil surveys https://www.nrcs.usda.gov/conservation-basics/natural-resource-concerns/soil/urban-soil-survey