Urbanization has always occurred on a landscape with strong legacies from both biophysical and social patterns and processes. Likewise, regional climate responds to urbanization creating a feedback mechanism in the self-organization of urbanized landscapes. Drawing primarily from research describing the central Arizona USA region I describe a case study of this process with reference to the Hohokam civilization who flourished in this region for 15 centuries, a nearly 500 year abandonment period, and the recent 100 year development of the modern Phoenix metropolitan region. A combination of topography and climate provide this region both with some of the largest radiant forcings on the planet in conjunction with perennial access to what until recently has been considered a limitless supply of water. The Achilles heel of this resource is the highly variable distribution of climate patterns, with both extensive flooding and droughts observed in the short period of the instrumented record. This extensive social legacy and climate variability is used to interpret the current dynamics of this region and the potential future trajectories for maximizing the distribution of ecosystem services and minimizing their associated costs.
Results/Conclusions
The effects of the unique climate template of central Arizona are evident in the expansion and collapse of the Hohokam and the legacy of this civilization as a landscape template for the initial structure of modern Phoenix. Phoenix is now home to more than 4 million people and is strongly affected by current climatic variability and rapid changes in landscape structure. Associated with the growth of Phoenix has been change in regional climate patterns through the creation of an urban heat island and the use of vegetation for its mitigation. Vegetation induced cooling can be substantial, with nearly 25C reduction in surface temperatures. The amount of vegetated cooling is associated with social processes clearly related to socioeconomic patterns; higher income neighborhoods have more vegetation and cooler temperatures than lower income neighborhoods. The recent history suggests that this neighborhood economic association with vegetation and climate is a new phenomenon that was not detectable as recently as 1970 and is on an increasing trajectory. Along with heat mitigation, this ecosystem services has a substantial cost in the requirement for irrigated water. Reconciling the benefits of and costs of supplying ecosystem services in regions strongly shaped by physical and social processes will be needed to improve decision making in a future changing world.
