Diagnosing a silent epidemic: the historical ecology of metal pollution in the Sonoran Desert

This research investigates the biophysical and institutional mechanisms affecting the distribution of metals in the Sonoran Desert of Arizona. To date, a long-term, interdisciplinary perspective on metal pollution in the region has been lacking. To address this gap, I integrated approaches from environmental chemistry, historical geography, and institutional economics to study the history of metal pollution in the desert. First, by analyzing the chemistry embodied in the sequentially-grown spines of long-lived cacti, I created a record of metal pollution that details biogeochemical trends in the desert since the 1980s. These data suggest that metal pollution is not simply a legacy of early industrialization. Instead, I found evidence of recent metal pollution in both the heart of the city and a remote, rural location. To understand how changing land uses may have contributed to this, I next explored the historical geography of industrialization in the desert. After identifying cities and mining districts as hot spots for airborne metals, I used a mixture of historical reports, maps, and memoirs to reconstruct the industrial history of these polluted landscapes. In the process, I identified three key transitions in the energy-metal nexus that drove the redistribution of metals from mineral deposits to urban communities. These transitions coincided with the Columbian exchange, the arrival of the railroads, and the economic restructuring that accompanied World War II. Finally, to determine how legal and political forces may be influencing the fate of metals, I studied the evolution of the rights and duties affecting metals in their various forms. This allowed me to track changes in the institutions regulating metals from the mining laws of the 19th century through their treatment as occupational and public health hazards in the 20th century. In the process, I show how Arizona’s environmental and resource institutions were often transformed by extra-territorial concerns. Ultimately, this created an institutional system that compartmentalizes metals and fails to appreciate their capacity to mobilize across legal and biophysical boundaries to accumulate in the environment. Long-term, interdisciplinary perspectives such as this are critical for untangling the complex web of elements and social relations transforming the modern world.