This doctoral dissertation research project will investigate the role of climate change and land use in the emergence and decline of the complex agricultural society at Cahokia, the largest prehistoric Native American settlement north of the Rio Grande. Cahokia was located in southwestern Illinois in the Mississippi River valley near present-day St. Louis. Agriculture began to develop in eastern North America around 4,000 years ago, and by 1050 CE, Cahokia had emerged in the central Mississippi River valley with a population of approximately 10,000 inhabitants, monumental earthworks, and an expansive trade network. Despite its role as a cultural and political center, Cahokia was almost completely abandoned by 1350 CE for reasons that remain unclear. One hypothesis is that prolonged drought or severe flooding caused Cahokia's decline. Other prehistoric agricultural societies appear to have been highly vulnerable to periods of water scarcity that reduced crop yields and triggered social instability. Environmental degradation caused by agricultural intensification may have exacerbated the effects of climatic change and further contributed to Cahokia's decline. To assess the potential role of climate change and resource overexploitation in the emergence and decline of Cahokia, the doctoral student will collect lake sediment cores from four oxbow lakes in in the Mississippi River floodplain along a transect beginning at Cahokia and moving southward towards areas that were less populated during the late prehistoric period. From all sediment cores, the student will develop long-term records of agricultural expansion and contraction (using fossil pollen, charcoal, and carbon isotopes) and hydroclimatic variability (using sediment mineral content and particle-size) that span the last two millennia. These high-quality records of changing land use, land cover, fire regimes, and hydroclimatic conditions that permit tests of hypotheses concerning the role of environmental change in Cahokia's abandonment.
This project will contribute to a broader understanding of the resilience and vulnerability of agricultural societies to land-use intensification and climate variability. By developing an understanding of why past agricultural societies collapsed, this project will provide insights into how to manage contemporary agricultural systems in order to increase their resilience in the face of environmental perturbations. This project lies at the intersection of the earth sciences, ecology, geography, and anthropology, and the researchers will present their work at national conferences to both social and natural scientists. The results of this research will be shared with the public through presentations at the interpretive center at Cahokia. All data will be made publicly available through the Neotoma Paleoecology Database, an online repository for data from lake sediment cores. As a Doctoral Dissertation Research Improvement award, this project will provide support to enable a promising student to establish an independent research career.
