By Yujuan Chen, Ph.D.
Soil is the brown infrastructure for the city. It has great potential to mitigate current and future climate impacts by sequestering carbon, improving water supply and water quality, supporting plant growth, enhancing food production, and maintaining healthy communities (Figure 1.). To better understand and utilize the potential of soils in the context of climate resilience, TreePeople, an environmental nonprofit organization (NGO) based in Los Angeles (LA), launched the “Healthy Soils for Healthy Communities Initiative” in 2019. This initiative is funded by Accelerate Resilience LA (ARLA), a sponsored project of the Rockefeller Philanthropy Advisors.
The first phase of the initiative was to conduct a needs assessment of LA soil. The objectives were to: 1) determine the current status of LA County soils; 2) identify the most pressing urban soil issues and community needs through community consultation and outreach; and 3) provide a framework for future work regarding urban soil research, policy, public education, and community engagement in the region (Figure 2.). We conducted online surveys, focus groups, various meetings and events, a review of the literature, and worked with universities, government agencies, NGOs, and community groups to achieve these objectives.
What Is the Current Status of LA Soils?
We analyzed 2016 LA County land cover data, the most recent soil survey of the LA metropolitan area conducted by USDA-Natural Resources Conservation Service (NRCS), synthesized the literature, and analyzed soil samples collected from the region. We found that:
- LA’s land and soils:
- 44% of LA County was covered by bare soil, which could be restored or sustainably managed.
- Soil sealing is another issue; for example, almost 50% of LA City’s land is covered by impervious surfaces such as buildings, roads, and other paved surfaces.
- LA soils have been highly modified (e.g., 45% human-altered soils in the southeastern part of LA County).
- Literature review:
- Among a total of 124 articles, reports, and other literature published between 1903 and 2020 on LA soils, soil properties and soil contamination were the most studied topics.
- A focus of public health and community concern is the presence of soil lead (Pb) throughout the LA metro region, where Pb concentrations in surface soils increased from 16 mg/kg between 1919 and 1933 to 79 mg/kg between 1967 and 1970.
- Soils analysis:
- 39 soil samples collected by the U.S. Forest Service from random points across the region were analyzed by California Polytechnic State University.
- The results suggest localized contamination of soils by several trace metals and relatively high soil pH, carbon/nitrogen (C/N) ratios, and carbon.
- The range of test results for all soil properties was wide and variable, suggesting the need for additional soil analyses to spatially predict soil properties across the region. This potential for soil contamination is exceptionally high in areas where vulnerable populations live, including disadvantaged, underrepresented and underserved communities.
What Are the Community Needs?
We conducted four county-wide online surveys (in both English and Spanish) with residents, educators, policymakers, and soil-related professionals. A total of 1,349 participants responded to the four online surveys, including 1,104 to the residential survey, 139 to the educator survey, 19 to the policymaker survey, and 87 to the professional survey (Figure 3.). The main findings include:
LA County Residents:
- LA County residents value green space: 85% of residents currently maintain a lawn, landscaped area, or green space, and maintain that space by watering and weeding.
- 73% of residents use the “green bin” for their green waste or allow green waste to compost in some form on the property.
- Resident knowledge about factors that affect soil health was low: 70% reported being not at all or only slightly knowledgeable.
- The majority of residents (76%) are very or extremely concerned about soil contaminants and pollution in their communities; however, only 12% of them have ever tested their soils.
- Interest in soil-related issues is high, with 76% of participants being either extremely or very interested in the topics listed on the survey.
LA County soil-related professionals:
- 77% of soil-related professionals are highly concerned about soil contamination, but only 17% believe their customers feel the same way. 85% of professionals typically use turf grass in their designs.
- Despite 70% of professionals of mulch, only 30% use the green waste from their projects as mulch or compost.
- Stated barriers to composting include: no facility available (48%), insufficient time (19%), and cost (14%).
How Can We Work Together to Address the Needs?
We propose an overall framework for phase two of this initiative to address the identified needs: the Los Angeles Urban Soil Collaborative. Under this framework, we propose a set of core activities, demonstration projects, community outreach programs, and the scaling up of these activities through the development of local, regional, national, and international collaborations. The good news is that phase two has been funded by ARLA, which will be carried out from this June to next November. For more information, please visit our website at: “Healthy Soils for Healthy Communities” Initiative.
- Chen, Y., R.V. Pouyat, S.D. Day, E.L. Wohldmann, K. Schwarz, G.L. Rees, M. Gonez, E. B. de Guzman, and S. Mao. 2021. Healthy Soils for Healthy Communities, Phase 1: Needs Assessment. TreePeople.
- TreePeople. 2021. Infographic: Healthy Soils for Healthy Communities, Phase 1 – Needs Assessment. Los Angeles.
About the Author
Dr. Yujuan Chen is the Principal Scientist in the Department of Policy and Research at TreePeople, an environmental non-profit organization based in Los Angeles. She is also a part-time lecturer in the School of Architecture at the University of Southern California, where she teaches Advanced Topics in Urban Ecology. Dr. Chen has a long-standing interest in urban forestry and urban soils. She is a co-author of the 1st global Guidelines on Urban and Peri-urban Forestry, which aims to optimize the contribution of forests and trees to sustainable urban development on a wide range of topics, including food, energy, water, land and soils, green economy, biodiversity, human health and well-being. Most recently, she initiated and is leading the “Healthy Soils for Healthy Communities Initiative” to study the potential of healthy soils in building climate resilience and healthy communities in Los Angeles. Prior to joining TreePeople, Dr. Chen held a range of positions with the Urban Forest Ecosystems Lab at Virginia Tech, the Urban and Peri-urban Forestry Program at the FAO of the United Nations, and the Community Forestry Program at New Jersey State Forestry Services. She holds a B.S. degree in horticulture from Beijing Forestry University, an M.S. degree in urban forestry from the Chinese Academy of Forestry, and a Ph.D. in urban forestry from Virginia Tech.
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