Community Resilience to Climate Change: Theory, Research and Practice

149 Assessing Vulnerability to Urban Heat: A Study of Disproportionate Heat Exposure and Access to Refuge by Socio-Demographic Status in Portland, Oregon by Jackson Voelkel, Dana Hellman, Ryu Sakuma and Vivek Shandas This article was originally published in the International Journal of Environmental Research and Public Health , 15(4), 2018. https://doi.org/10.3390/ijerph15040640 This work is licensed under a Creative Commons Attribution 4.0 International (CC BY 4.0) license ABSTRACT Extreme urban heat is a powerful environmental stressor which poses a significant threat to human health and well-being. Exacerbated by the urban heat island phenomenon, heat events are expected to become more intense and frequent as climate change progresses, though we have limited understanding of the impact of such events on vulnerable populations at a neighborhood or census block group level. Focusing on the City of Portland, Oregon, this study aimed to determine which socio-demographic populations experience disproportionate exposure to extreme heat, as well as the level of access to refuge in the form of public cooling centers or residential central air conditioning. During a 2014 heat wave, temperature data were recorded using a vehicle-traverse collection method, then extrapolated to determine average temperature at the census block group level. Socio-demographic factors including income, race, education, age, and English speaking ability were tested using statistical assessments to identify significant relationships with heat exposure and access to refuge from extreme heat. Results indicate that groups with limited adaptive capacity, including those in poverty and non-white populations, are at higher risk for heat exposure, suggesting an emerging concern of environmental justice as it relates to climate change. The paper concludes by emphasizing the importance of cultural sensitivity and inclusion, in combination with effectively distributing cooling centers in areas where the greatest burden befalls vulnerable populations. Keywords: urban heat; vulnerability; environmental justice; heat exposure; resilience 1. INTRODUCTION Extreme heat poses a growing threat to human populations, with numerous implications for public health, economic stability, and quality of life [1,2,3]. Past heat waves have had devastating, deadly outcomes worldwide [4,5,6], and such events are expected to increase in intensity, frequency, and duration as climate change progresses [7,8]. Although human settlements of any type may experience the negative effects of extreme heat, these are and will continue to be most pronounced in urban areas, the development practices of which are highly correlated with rising temperatures [9,10,11]. Currently, more than 50% of the world’s population is located in urban areas, and that figure is expected to reach over 66% by 2050 [12]; with so many people potentially at risk of exposure, it is imperative that local governments and planning practitioners recognize varying degrees of vulnerability among urban residents. Urban heat events—defined as those above the 90th percentile of historic temperatures [13]—are an environmental stressor, placing economic, infrastructure, and human health burdens on society [14,15,16]. As a stressor, urban heat can create vulnerabilities, which may be understood as a combination of three factors [17]: exposure, sensitivity, and adaptive capacity. Exposure refers to an individual’s contact with a stressor, either from living, working, or spending time in an affected location. Sensitivity is the point at which exposure becomes dangerous to an individual’s health [18]. Finally, adaptive capacity refers to one’s ability to change exposure or sensitivity, or to cope with an extreme event. Regarding urban heat, indicators believed to enhance adaptive capacity include high income, social cohesion, and knowledge of hazardous environments [19,20]. Given these conditions, it may be reasonable to categorize extreme heat exposure as an environmental justice issue. The phenomenon central to this study is the urban heat island (UHI) effect, which has been known to researchers since the mid- 19th century, and indicates a strong correlation between urban environments and high temperatures [21,22]. Impervious surfaces and anthropogenic activity within cities portend rising temperatures, as does the relative scarcity of heat-ameliorating elements such as trees and grasses [23,24,25]. A higher frequency of regional extreme heat events, as such, will amplify temperatures [8], and generate UHI in areas that have greater amounts of heat absorbing surfaces. While early studies focused on the comparative temperatures between urban and non-urban regions, the emergence of mobile sensors, highly accurate global positioning systems, and computational software allows for the comparison of intra-urban spaces, measuring variation in temperature distribution across a single city [26,27]. Past research has utilized infrared satellite data for this purpose [10,28,29], though vehicle-based traverse measurements (used in this