The Fourth Assessment of the IPCC has firmly established the anthropogenic causes of climate change (IPCC, 2007), which involve increasing temperatures and shifting precipitation patterns in many regions (Bates et al., 2008). In addition to this climate change signal, our global cities are experiencing urban heat island (UHI) stresses, leading to human suffering and death during heat waves, and increased energy consumption in the use of air conditioning. Studies have documented how the UHI has raised urban temperatures by more than 0.1 to 0.4 °C per decade (Akbari et al., 2001), with minimum city temperatures more than 3°C than surrounding rural areas (Rosenzweig et al., 2005).

My ecological engineering research has the capacity to address both human discomfort and health issues related to the UHI as well as improve the urban ecosystem. Several studies have shown that increasing tree coverage in urban areas will mitigate the UHI effect (Heisler et al., 1994; McPherson et al., 2005; Solecki et al., 2005; Taha et al., 1996); however, none have completed a water budget to ensure tree systems have adequate water to provide the cooling services of shade (i.e., direct cooling) and evapotranspiration (i.e., indirect cooling). In a study of UHI cooling options for Sacramento, CA, Akbari (2002) noted the city could increase tree cover from 13 to 36%, and in Los Angeles, CA there is an initiative to plant 1 million trees to address UHI and air pollution problems (USDA, 2006). For both of these cases, as well as future scenarios, research into planting and management of trees is complementary, providing a low cost, self-organized method of sustaining the tree cooling services.