Angela Clapp Street trees and the built environment Spring 2010 Assessing the social impacts on urban street trees through the built environment in West Oakland, CA Angela Clapp ABSTRACT Urban areas involve a complex interplay of social, natural, and physical systems, and finding ways to address and understand the urban street tree dynamics within urban areas is a difficult task for urban foresters. To maximize the benefits of the urban forest, and uncover ways that an urban area’s social structure affects the physical and urban environments, new strategies for exploring these systems must be developed and tested. In this study I address social forces on the built environment and explore if similar social preferences affect the survival and dynamics of street trees in West Oakland, CA. Household and block-level analysis made it possible to assess the small-scale heterogeneity of maintenance due to residents’ perception of their environment, their lifestyle choices, and their territoriality. After analysis of many factors, I found an unusually low mortality rate, as well as linkages between trees, land use, and front yard green space, and between trash level, property maintenance, and front yard green space. These linkages suggest a connection between resident’s level of care on their own land and on their block, part of their lifestyle choice. However, a larger study size and perhaps longer timescale would be needed to link tree mortality to these factors. KEYWORDS urban forestry, tree mortality, land use, urban ecology, lifestyleAngela Clapp Street trees and the built environment Spring 2010 2INTRODUCTION ‘Urban areas’ are defined as all cities, towns, and suburbs—all places where people live in dense populations. While few environments world-wide have escaped human influence, in urban areas humans have fundamentally altered and engineered the environment to accommodate for human activity, creating a ‘built environment’. This term may suggest that “natural” systems have been superseded in cities, and although an area’s transformation from natural to urban invariably involves reducing vegetation and disrupting natural processes, ecological processes still persist in urban ecosystems (Dow 2000). The purpose of this study is to explore how the structure of the urban environment affects the function and dynamics of urban street trees, a part of a city’s larger urban forest and an example of a natural process within a city’s complex social and physical structure. Though urban areas have the same general factors (low vegetation/high built landscape, high population density), urban ecosystems are remarkably complex and vary dramatically over a variety of spatial and temporal scales (Grove and Burch 1997). Recent efforts have combined practices in ecology and social science with landscape analysis of spatial heterogeneity to study urban ecosystems and the changing, dynamic forces that shape them. This “urban ecology” approach aims to understand the interconnectivity between spatial heterogeneity and biophysical and socioeconomic processes, the hierarchy and subtleties of human influence as well as the forces that affect human behavior, and the consequences for physical and natural systems (Grove and Burch 1997). Applying this approach to the urban forest necessitates knowledge on the ecological response of trees in urban areas, which means assessing the social factors that influence and change the physical environment and how the physical and social systems affect tree health directly and indirectly. An urban forest consists of all public and private trees within an urban area. Much like the study of cities themselves with urban ecology, the study of trees within cities, called ‘urban forestry’, is a relatively new and multidisciplinary approach. Urban trees can provide many benefits to society, but cities provide a harsh growing environment for trees for many reasons, such as: limited space for growth, excess pollution, soil compaction, nutrient deficiency, limited water, and damage through vandalism and other human action (Nowak et al. 1990). Urban foresters work to understand what affects urban tree survival and overcome obstacles to treeAngela Clapp Street trees and the built environment Spring 2010 3growth to maximize the many benefits of urban trees. Urban trees can improve air and water quality, offset the formation of urban heat islands, improve human health, create aesthetically pleasing environments, increase property values, create a stronger sense of community and connection to nature and others, and empower communities, among other social and quality-of-life benefits (Dwyer et al. 2000, Dwyer et al. 1992, Kuo 2003). However the sociocultural/socioeconomic forces within an urban area mean that distribution of critical resources is not equitable, and the urban forest is no different (Pickett et al. 2001). Gaining a better understanding of the social and physical factors that affect tree health is critical for urban foresters to efficiently and effectively manage the urban forest resource. Urban forests display spatial heterogeneity within and between cities, neighborhoods, and even households (Picket et al. 2001). This heterogeneity is in large part due to differing social contexts, and differences among the groups responsible for management (Picket et al. 2001, Dow 2000). Since the majority of the urban forest is owned and managed by urban residents (Dwyer et al. 2000), looking at the physical and social environment on a small scale may be most useful for deciphering the social impact on urban trees. Social scientists have used concepts of social hierarchies (wealth, power, status, knowledge, and territory) to study how societies become differentiated, and these socioeconomic ideas have been used to explain heterogeneity in urban vegetation cover (Grove and Burch 1997). For example, population density, socioeconomic status, and level of community involvement in planting have all been shown to affect tree health and mortality (Grove et al. 2006, Sklar & Ames 1985). Human preferences and actions shape both the urban forest and the built environment, and yet no known studies relate the two systems. If assessing the built environment of a community provides real insight into the social preferences that also determine the health of the urban forest, it could provide urban forest management agencies with a cost-effective and
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