City's mysterious fate linked to flood

April 25, 2014

Jack Williams, director of the Nelson Institute Center for Climatic Research and a professor of geography and environmental studies, is coauthor of a new study examining prehistoric and historic land use in the Cahokia region of Illinois, the largest prehistoric settlement north of Mexico. Williams and colleagues from UW-Madison and Washington University studied sedimentary records from Horseshoe Lake, an oxbow lake adjacent to the Cahokia site, to evaluate the impacts of deforestation and farming on terrestrial ecosystems.

Their findings, published April 10 in the journal Geology, document pronounced vegetation changes over the past 1,700 years driven primarily by land use, including 900 years of sustained prehistoric human impacts.

The Horseshoe Lake record indicates that regional agricultural activity began abruptly at A.D. 450 and intensified over the following centuries, well before the formation of Cahokia and other large prehistoric settlements. A major flood event circa A.D. 1200 coincided with the onset of agricultural contraction and Cahokia's decline. 

Samuel Munoz, a UW-Madison doctoral student in geography and a member of Williams' lab, is lead author of the study.

Read a LiveScience report about the research.