New Evidence Shows Deforestation Didn’t Cause Cahokia’s Collapse For several decades, one of the most persistent theories of Cahokia's collapse has blamed self-inflicted ecological disaster. By studying soil samples, Caitlin Rankin’s research debunks that. She discussed it on "St. Louis on the Air."

New Evidence Shows Deforestation Didn’t Cause Cahokia’s Collapse

What caused residents to abandon the ancient settlement that made the area near Cahokia, Illinois, home to the biggest city in the Western world? At its peak approximately 1,000 years ago, the settlement was bigger than London. But by A.D. 1400, it was virtually deserted.

Cahokia’s collapse has long been a subject of speculation. For several decades, one of the most persistent theories has blamed self-inflicted ecological disaster. First suggested by researchers at Southern Illinois University-Edwardsville in 1993, the theory held that the Mississippians who inhabited the city cut down forests in the nearby uplands, leading to erosion and flooding.

But the evidence underlying the theory was negligible, said geoarchaeologist Caitlin Rankin. The researchers knew that the people living in the area used wood, and that “there was increasing use of upland trees, happening more towards the end of Cahokia’s occupation,” she explained on Tuesday’s St. Louis on the Air.

There was, she added, modern-day precedent. “The narrative of deforestation leading to erosion, leading to sedimentation, leading to flokenoding, is one that we see happening a lot, particularly here in the West, but normally it’s related to really heavy clear-cutting trees, and also mining practices.”

The problem? There’s no evidence the Mississippians living in the Cahokia area engaged in anything like that. Rankin’s recent research in the journal Geoarchaeology suggests just the opposite.

As a doctoral student in geoarchaeology at Washington University, Rankin made a series of excavations around an earthen mound in the Cahokia Creek floodplain in 2017 and 2018. It was painstaking work, digging by hand deep into the layers of soil. But it led to some conclusions that counter the 1993 theory. She found no evidence of erosion or unstable soil until 1850 — long after Europeans began to alter the natural environment. And the evidence of flooding she found happened early in Cahokia’s construction, suggesting it did not deter settlement nearby.

The work pushes back not just on the 1993 theory, but on the idea that the ancient Cahokians’ demise offers an ominous foreshadowing of our modern era. Rather than a cautionary tale, they instead may offer a model we should follow.

“I think it’s a Western perspective that tends to see humans as inherently bad for the environment,” she said. “We’re really quick to agree with these narratives that humans caused their own disaster, because it is a situation that we are living in now. However, it’s not fair for us to push those perspectives on other people with different cultures and people of the past. We should be asking questions and testing the assumptions so we can actually learn from people who learned differently from us, and in some cases more sustainably.”

Rankin sees increased interdisciplinary work as key to preventing false narratives from taking hold in the future. Geoarcheaologists used to be brought on as consultants on archeological projects, she said. Now, they increasingly help to guide the work.

“We’re not just consultants anymore,” she said. “We’re becoming much more involved with the theory and the practice.”

Rankin said she found her interest in the field early. Growing up in western Pennsylvania, she was fascinated by her father’s work operating heavy equipment and attended Beloit College in Wisconsin to pursue her interest in anthropology.

She’s now earned her doctorate and works as a research geoarchaeologist for the Illinois State Archaeological Survey, a part of the University of Illinois. She said she couldn’t be at a better place to do meaningful research.

“When it comes to archaeology, the Metro East is where it’s at,” she said.

St. Louis on the Air” brings you the stories of St. Louis and the people who live, work and create in our region. The show is hosted by Sarah Fenske and produced by Alex Heuer, Emily Woodbury, Evie Hemphill and Lara Hamdan. The audio engineer is Aaron Doerr.