Do scientists need to do a better job making the link between green infrastructure and brown infrastructure?

Susan Day, Forest Resources Management, University of British Columbia, Vancouver, BC, Canada, Erica L. Wohldmann, California State University, Northridge, Kirsten Schwarz, Departments of Urban Planning & Environmental Health Sciences, University of California, Los Angeles, Los Angeles, CA and Yujuan Chen, TreePeople, Beverly Hills, CA

Background/Question/Methods
Urban soils play an essential role in the ability of green infrastructure to support ecological processes and ecosystem services. As such, soil can be considered “brown infrastructure,” the the quality of which can enhance or impede the function of green infrastructure. For example, soil rehabilitated post-land development can support a doubling of tree growth when compared to unmanaged soil in just a few years. Soil quality influences hydraulic conductivity of soils, with profound effects on green infrastructure function. Although these connections are numerous and significant, they may be underappreciated. We used focus groups and surveys in Los Angeles County, CA to explore the perception of the role of urban soils in supporting green infrastructure. Residents, educators, policy-makers, and natural resource professionals completed distinct surveys resulting in 1,349 respondents. In addition, 41 individuals from three stakeholder groups (technical experts and policy-makers; landscape, gardening and urban agriculture practitioners; and community and coalition members) participated in focus groups to elucidate perceptions of soil and its contributions to plant systems. Synthesized focus groups then identified cross-cutting themes. We analysed results to assess the strength of connections respondents made between brown and green infrastructure.
Results/Conclusions
Angelenos recognize the connection between soil health and green infrastructure. Plants and trees growing was the most commonly selected indicator of soil health. Virtually all respondents (99%) were interested in “how improving your soil quality can benefit your plants/trees”. Other soil-health-related benefits were of high interest including: weed control and drought resiliency. The vast majority of residents maintain a landscaped area or lawn through irrigation or weed removal (85%), although only 18% grew vegetables and 15% reported trees in their landscape. In spite of the high level of interest in plants, landscaping, and better landscape maintenance—all of which are known to be very responsive to soil quality—most residents had little soil knowledge and many had never sought out soils information in the past. Focus groups revealed concerns about direct connections between soils and public health (i.e. the effect of soil contamination), but did not identify the indirect connections through green infrastructure as a high-priority issue. This may, in part, be because information concerning the magnitude or significance of the impacts of soil health on green infrastructure may not be readily available to stakeholders. Implications for policy-makers, educators, and the research community will be discussed.