An Assessment of Climate Vulnerability in the Middle San Pedro River

This study examines the vulnerability of a local community in southeastern Arizona to climatic variability in climate change. The research team reviewed the history of the settlement of the Middle San Pedro River Valley (MSPRV), then traced the social dynamics that have led to the current situation. This integrated assessment reveals both the cross-sectoral patterns of climate vulnerability and the changing level of vulnerability through time. Examination of the MSPRV clearly demonstrates the cumulative process of buffering against the vagaries of the desert environment. Such buffering has been more successful in some sectors than others. This report highlights the disadvantaged position of ranchers and some farmers relative to urban dwellers. For most of the residents of the MSPRV, sensitivity to climate is subtle, and climate change and increasing climate variability have been gradual processes to which people have adapted their lives. The population of the desert SW has grown with the availability of life pumps, air conditioners, rapid automobile transport, and other kinds of technological advances that make living in the area more comfortable and convenient. As a result, this and other communities are not immediately vulnerable to continue variability to a significant degree, as long as changes continue to happen gradually, giving people communities time to build the necessary buffers. This report further documents the movement of people and livelihoods away from the more climate vulnerable sectors of the economy. Thus, ranches are rapidly becoming “ranchettes” and farms are becoming “horse properties” as former livelihoods shift to quality-of-life residence preferences. Facilitated by improvements in transportation infrastructure, small communities of the MSPRV have transformed from traditional livelihoods to a service economy based on tourism, retirement communities, and commuters from nearby Tucson. In this context, the research team examined the hypothesis that this social dynamic throughout the valley might ultimately increase the vulnerability of the region to climate variability and change. Based on current knowledge of hydrology of the watershed, there will be an increase in recharge deficit of the fossil water aquifer (as opposed to the alluvial aquifer of the river valley), but the point at which wells go dry or pumping costs get to high lies well into the future. Other than in the ranching sector, it was not possible to determine if there is a true vulnerability based on the underlying scarcity of the resource base; for lack of better physical information, the report cannot conclude that there is a discrepancy between actual vulnerability and perceived vulnerability. City planners and utility managers, as well as the real estate and business communities, do not perceive climate to be a matter of concern. As development proceeds, people make concessions to factors related to climatic variability, but not necessarily because they're concerned about climate. Wells, air conditioners, evaporative coolers, space heaters, and other technologies have buffered climate impacts to the extent that climate variability has become routine and mundane. The insights from the study suggest that an enhanced climate forecasting system could contribute to the existing protection of climate vulnerability buffers, as an aid to mitigate impacts of severe climatic extremes (prolonged drought, torrential rains and flooding, etc.). Seasonal forecasts based on El Nino or La Nina events (or influenced by other climatic phenomena) have the highest potential for most vulnerable sectors (i.e., ranching) if the quality of information is accurate enough to inform decision-making. For example, prior knowledge of an extended drought could allow ranchers farmers to develop coping mechanisms that serve to reduce or minimize the economic consequences. However, before they will use climate forecast information, stakeholders in the MSPRV require accurate climate forecasts that are easily available and understandable.