How do soils and humans impact one another?

Soils are a finite resource, and only renew over centuries or millennia. Soils provide many “services” to humans, yet it is largely an ignored resource. Some of the services soils provide are:

  1. Capturing and cleaning rain and snowfall,
  2. Providing structure to grow our food,
  3. Holding carbon in the form of organic matter (carbon sequestration), and
  4. Providing a home to soil microbes, insects, and soil-dwelling animals.
graphic with several animated images and explanations depicting the importance of soil
Graphic from Dr. Wohldmann’s presentation showing the importance of soils: food production, storing and filtering water, hosting biodiversity, providing a foundation for infrastructure and more. Provided by Erica Wohldmann

It’s easy to see soil out in the countryside of rolling farm fields. But more than 80% of Americans live, work, and play in urban areas. This can create a disconnect between people and soils – to the detriment of both.

Rarely do policymakers, city planners and urban residents consider soil as a living resource, connected to the services it provides. I worked with a team of researchers to study how people view and interact with soil. The results can help us know what education and policies to develop to protect this natural resource.

We surveyed four groups: residents, professionals connected to soil science disciplines (like planners and landscape designers), policy makers, and educators. Our questions ranged from their knowledge and values around soils, to budgets and practices.

Our study area was Los Angeles County. This county varies widely – from strict downtown cityscapes to beaches or forests. It even includes Catalina Island – a 45-minute boat ride off the coast, which has some residential and commercial development as well as protected land.

water runoff flowing into stormwater drain on road curbside
Because of impervious surfaces like roads, parking lots and buildings in urban areas, cities have built stormwater systems to capture water runoff. Credit: SV Fisk

With regard to land cover, one of the challenges of Los Angeles County is the amount of land covered with impervious surfaces such as cement and asphalt – buildings, roads, parking lots, etc. This means the rainfall we do get is often not collected in the soil but moves through our stormwater management system. But, with the number of forests we have in the county, almost a quarter of our land is covered with trees, and another 16% has shrubs or grasses. About 11% of our land is bare soil.

Preliminary results from our survey (our research is ongoing) suggests that most people surveyed maintain some type of green space. Some were using fertilizer, including compost and worm castings. A smaller group used pesticides, mostly only as needed. Many respondents observed earthworms in their soil – a sign of healthy soil. Some even observed fungi, which can sometimes be harder to see.

Los Angeles County has a “green bin” collection service that accepts yard waste and, in most cases, plant-based kitchen scraps. Seventy-five percent of respondents said they use the bins for yard waste. However, only 50% said they use it for plant-based food scraps. Curbside composting bins can serve as an excellent way to recycle valuable nutrients, create compost for residents – and keep waste out of landfills.

hand holding clump of compost. compost is beneficial to both humans and soils
Results of Dr. Wohldmann’s ongoing study showed that many residents of Los Angeles County were using compost in their green spaces. Credit: Jodie Reisner

Happily, a majority of respondents are concerned about the health of their soil and of the planet! Almost 75% of the respondents reported being concerned about soil health and contaminant. Even more were either “extremely” or “very” concerned about broader environmental issues.

Our work to understand and inform the people of Los Angeles County on best practices is ongoing – whether resident, professional, policy maker or educator. All these groups contribute in unique ways to building a society that both uses and preserves our precious limited soils.

To learn more about this ongoing work, visit

Erica Wohldmann, California State University, Northridge

The partners in this group are Tree People, California State University-Northridge, UCLA, and the The University of British Columbia. Their funding comes from Accelerate Resilience LA, a sponsored project of Rockefeller Philanthropy Advisors.

Read more about another program: San Antonio’s efforts to reduce solid waste. This blog is based off a poster presentation Dr. Wohldmann made for the ASA-CSSA-SSSA 2020 Virtual Annual Meeting held Nov. 8-13, 2020.

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