In a new article published in the International Journal of Biometeorology, SSI Assistant Professor Darren Ruddell shows that despite the best intentions of drought-tolerant landscaping programs, they do not automatically result in reduced water or energy consumption in arid cities. The paper has broad implications for urban planning to reduce water and energy consumptions and illustrates that factors other than landscape type might be better targets for policy interventions.
The conventional view is that water and energy use are inversely correlated, that neighborhoods with drought-tolerant landscaping save water, and that newer residences consume less energy. Drawing on a combination of data sources from the Phoenix, Arizona region, Ruddell and his colleague, Grady Dixon of Mississippi State University, found that in fact neighborhoods with high water consumption also showed higher energy consumption, those with drought tolerant landscaping did not consume the least energy, and that newer residences consumed more energy than old.
These counterintuitive results suggest that other factors outweigh the lower water use of drought-tolerant landscaping. Newer residences have more amenities, and despite having better insulation, energy-efficient windows, and more efficient appliances, they result in more energy consumption per capita than older residences. In short, a large “green” house with water saving landscaping is still a bigger resource consumer than an older (smaller) home that uses more water on landscape. This puts urban planners in the uncomfortable position of seeing the modest benefits of well-intentioned programs to reduce water and energy use being dramatically undermined by patterns of increased consumption associated with larger and larger single-family residences.