Beyond the park: exploring informal green spaces, the provision of ecosystem services, and socio-spatial equity in U.S. cities

Abstract

With accelerating global urbanization and development, urban parks are increasingly recognized as essential for promoting ecological resilience, public health, and social equity while serving as critical habitat for wildlife. Parks provide a myriad of ecosystem services to community members, from reducing heat islands and flood risks to promoting exercise and recreation. However, urban parks are often inequitably distributed in terms of size, quality, and access. Due to these inequities, some researchers have explored other, more informal green spaces to fill the void. Informal green spaces are transient areas of spontaneous vegetation that form due to other land uses such as street and railroad verges, irrigation ditches, and vacant lots. While these spaces are often overlooked, they may provide substantial ecosystem services in areas that have traditionally lacked them due to reduced access to managed park space. However, few studies have explored the potential equity of access and the presence of these spaces. Further, few have explicitly compared the ecosystem service provisioning of informal green space to that of formal green spaces in our cities. This dissertation arose from a desire to understand how informal green spaces serve urban inhabitants, both relative to formal green spaces, and whether they might offer untapped potential to mitigate environmental injustices in urban environments. This dissertation explores the structure, function, and equity implications of informal green spaces within urban environments, positioning them as critical but often overlooked components of sustainable city planning. Across three empirical chapters, I examine how informal green spaces compare to formal green spaces in terms of spatial distribution, ecological characteristics, and socio-economic outcomes. In Chapter 1, I analyze and compare the landscape metrics of both informal and formal green spaces across ten U.S. cities, quantifying their quantity, shape, configuration, and fragmentation. I also explore the spatial equity of informal and formal green spaces across each city using the Gini coefficient, a metric designed to assess spatial inequities of a variable across a landscape. The findings reveal that informal green spaces often comprise a greater total area within census block groups across cities. Further, informal green spaces are more equitably distributed than formal green spaces, though they are also typically more fragmented. The multiple linear regression models predicting the equity of green space distribution through the Gini coefficient demonstrate that equity is strongly influenced by race and income, with Whiter and wealthier communities generally benefiting more. These results underscore the need to formally recognize and integrate IGS into urban green infrastructure planning to reduce long-standing spatial inequities. Chapter 2 focuses on Fort Collins, Colorado, to evaluate how vegetation structure within IGS and FGS influences ambient noise levels. Using remote sensing and GIS data, I find that although IGS tend to have taller canopies, they are also slightly louder on average. Surprisingly, canopy height alone does not predict noise attenuation; vegetation density and habitat type emerge as stronger predictors. Communities with higher social vulnerability experience greater noise exposure, highlighting inequities in green space quality and environmental protection. These findings call attention to the importance of vegetation structure in environmental justice and suggest new directions for designing green spaces as acoustic refuges in cities. Chapter 3 further investigates Fort Collins by examining the relationship between green space characteristics, socio-demographics, and urban heat island (UHI) effects. While IGS and FGS cover similar areas, IGS are significantly more fragmented. Gini coefficients confirm that IGS are more equitably distributed, particularly in lower-income neighborhoods. Median income consistently predicts both green space equity and UHI intensity, and spatial configuration metrics like edge density influence localized heat exposure. These findings demonstrate that IGS can serve as critical, if underutilized, assets in climate resilience strategies, especially for vulnerable communities facing disproportionate heat burdens. Collectively, these studies demonstrate that IGS play a meaningful role in mitigating environmental inequities related to access, noise, and urban heat. However, realizing their full potential will require intentional recognition, integration, and management in urban planning. The findings advocate for a multifaceted, equity-driven approach to urban greening that includes both formal and informal green spaces to build more resilient and inclusive cities.