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Climate Change and U.S.-Mexico Border Communities 357with neighborhood socioeconomic characteristics. In other words, affluent areas wereless densely settled, had lower mean temperatures, and thus had lower vulnerabilityto heat stress, while low-income areas had more rental housing, greater prevalence ofmulti-generational families sharing a household, and a higher prevalence of non-Englishlanguage speakers (Harlan et al. 2008). These findings point to the need for climatehazards and risks to be communicated to the public in a way that respects the diversityof media, technology, and languages in used in the region. In the long run, these problemscould be reduced through improved urban development and investment in marginalizedareas.Infrastructure. Dense urban areas in the border region contain substantial populationswho are vulnerable to natural disasters linked to climate change because theylive in substandard housing in floodplains or on steep slopes or in housing located inareas on the urban periphery that are susceptible to wildfires (GNEB 2008). Tijuana andNogales, two border cities experiencing rapid population growth, have received an influxof immigrants seeking employment in the maquiladora industry. Many settle ininformal (unplanned) colonias (border-region residential communities that are economicallydistressed and usually underserved by infrastructure) with unsuitable topography,characterized by steep slopes and canyons. With few measures to control erosion,extreme rain events and the prevalent topography lead to runoff and floods during extremeconditions (Cavazos and Rivas 2004; Lara and Díaz-Montemayor 2010).Border cities are also underserved by water and wastewater infrastructure as wellas other urban infrastructure such as paved streets and lighting (Lemos et al. 2002; Jepson2012). In 2007, for example, the Border Environment Cooperation Commission estimatedthat there was nearly $1 billion in unmet investment in water and wastewaterinfrastructure in the border region (BECC 2007). An estimated 98,600 households in theUnited States and Mexico border region lacked safe drinking water, and an estimated690,700 homes lacked adequate wastewater collection and treatment services (EPA2011). Thus, on both sides of the border, large numbers of residents do not have safepotable water piped into their homes and lack proper sewage collection and treatmentservices (GNEB 2008).Informal colonias from Tijuana to Nogales to Juárez often are off-the-grid for water,sanitation, and electricity and rely on purchased water from trucks at relatively highercost than municipal tap water (Cavazos and Rivas 2004; Collins 2010; Wilder et al. 2012).Water-scarce states like Sonora have water rationing in major cities—including the capital,Hermosillo, and its largest border city, Nogales—based on a system known in Spanishas tandeo. Basic infrastructure is limited in the informal colonias, and construction onunsafe hillsides in floodplains leads to increased risk to human residents from severeflooding when it rains. Flooding of unpaved roads may disrupt water-truck deliveriesfor households not on the municipal grid.Economy. The border is a region of dynamic growth in both industry and employment.The region is of critical value to the global economy and both countries’ nationaleconomies due to its production of agriculture and manufactured goods. Its economicsignificance therefore enhances its exposure to climatic stress. Its integration into theglobal economy means that climate stresses have potential impacts beyond local borders