Among the significant discoveries resulting from the first three years of Central Arizona – Phoenix LTER studies, three stand out for their scientific generality and potential social relevance. In a comprehensive study of the nitrogen mass balance for the CAP ecosystem, it was found that anthropogenic sources far outstrip natural sources of N. More interestingly, the vegetation and soils in the city are likely sinks for retaining much of the enormous production of N from combustion-derived NOx production (Baker et al. in review). This detailed N mass balance is a first for an agro-urban ecosystem and is therefore a landmark effort. Such information can be used to help guide responsible use of commercial fertilizers by accounting for the use of high-nitrate content groundwater for irrigation.
A study of the growth of the Phoenix metropolitan area determined that the spread of the city through the construction of new single-family houses at the periphery could be characterized by a “wave of advance” model (Fig. 1; Gober et al. 1998). Related studies show that this wave is instrumental in determining changes in key ecological variables such as microclimate, soils, and vegetation cover. The initial data for this came from county records but is now being supplemented by CAP LTER researchers who use sequences of aerial photos to monitor land-use change in greater detail. At the same time our remote sensing team is developing a classification scheme to carry this study forward into the future in a more time efficient and comprehensive manner.
A third key study has looked at whether there is a systematic relationship between the distribution of environmental hazards and residential location of minority groups or economically disadvantaged families. Examining both sources of toxic releases and patterning of air pollution, it is clear that ethnic minorities and the poor are exposed to greater environmental hazards (Fig. 2; Bolin et al. 2000). As the pattern of industry changes, however, this correlation may change as well. With the shift from traditional smokestack polluters to new economy chip manufacturers comes a greater tendency for polluters to be located in more affluent neighborhoods. Part of our study is looking at how local residents perceive these risks and the type of action they take to ameliorate the situation.
Due to the urban location of the CAP LTER, the results of these studies and many others are of immediate service to society. Understanding the ecological changes that accompany new housing and urban sprawl will allow for more rational city planning, while knowledge of nutrient sources and sinks in the urban environmental will lead to more efficient construction of infrastructure. The insights we are gaining on the nature of environmental risks and how they are differentially borne by citizens will enhance city planning and possibly an enhanced quality of life. The CAP LTER project also offers a stimulating research and learning environment for a diversity of graduate students, postdoctoral associates, and K-12 schoolchildren. This year, we are expanding those opportunities through an IGERT graduate program focused on training professionals to work with issues of urban ecology. We have an extremely active K-12 program called “Ecology Explorers” that has worked with schoolteachers from throughout the urban area to enhance science and math education through inquiry-based, hands-on educational opportunities associated with our research project.