Thousands of cultural sites from the pre-contact and historic eras made up of house foundations, trash-filled storage pits, cooking hearths, and living surfaces are still preserved just below the surface across Illinois. Some of these sites offer evidence of the daily lives of the people that called the state home for millennia – including the homes of Indigenous Illinoisans and, more recently, historic-era Euroamericans, Black Americans, and others going back 13,000 years. Many of these sites are also sacred places of great value to descendant communities—mounds, burial grounds, and shrines—places where people modified the landscape in sometimes spectacular ways or imbued spaces with meaning by virtue of their ancestors and cultural objects they left behind.
These buried sites and artifacts represent the material record of past human lives and cultural practices and are an invaluable, non-replaceable resource for anybody—most certainly archaeologists—interested in answering questions about how humans adapted to (or sometimes created) changes in their physical and social environments. These sites also tether families and communities to landscapes, stories, and history more generally. However, this important and fragile record of unwritten human history is under threat of disappearing. The culprit? Climate change. In Illinois, factors like erosion and flooding are becoming increasingly common and intense, and threaten to erase much of our shared cultural heritage.
Today, 75 percent of Illinois is farmland, and for much of the last 200 years farmers cultivated their fields using plows that turned over the soil and left it—and the archaeological remains of thousands of habitation sites—exposed to melting winter snows and heavy spring rains. Conservation practices deployed since the 1970s like no-till agriculture, conservation tillage, and cover crops are now used on roughly half of Illinois farms and have helped to slow the rate of topsoil erosion, but have not stopped it. The pace of erosion-induced landscape change is often subtle as topsoil in farmers’ fields slowly degrades. However, with the increasing severity of precipitation events, the pace of erosion is accelerating. Record-breaking rains and flash floods can lead to staggering amounts of erosion during single events. The earth is washing away, a little (or sometimes a lot) at a time.
Large swaths of the state—areas where the soil is easily eroded, where farm field slopes are particularly steep, and where there are many cultural sites of historic significance—are poised to suffer significant impacts in the coming decades (see examples in Figures 1-2). And with every fraction of an inch that washes downstream, the farmer’s plow goes a little deeper each year. And while farming is a major source of erosion in Illinois, it is not the only one. Deforestation, loss of other habitats such as native prairies, and construction associated with development all play a role as well.
To better understand the threat to Illinois’ cultural heritage posed by climate change, the Illinois State Archaeological Survey (ISAS) has begun modeling which parts of the state are most vulnerable to increased topsoil erosion (Figure 3). In our map of predicted erosion potential for Illinois, several areas stand out as particularly vulnerable, including the steep, intensively farmed slopes of western and northwestern Illinois and the more rugged terrain along the Kaskaskia and Embarras River drainages in the southern part of the state. However, zooming in to a smaller area (Figure 3 inset) shows that there is a lot of local variation—generally speaking, places with steep slopes that are under cultivation are more susceptible to erosion than places that are flatter or benefit from forest cover or other surfaces which hold topsoil in place. Even if nothing were to change, erosion poses a much more acute threat to buried archaeology in some parts of Illinois than others. Given current projections for climate change, these impacts will likely be accelerated, and many sites will disappear in the coming years. In fact, 80% of pre-contact-era, Native American archaeological sites and 82% of historic-period sites lie in areas with high predicted erosion potential in our model (visit the IAPM web viewer to compare erosion potential to predicted site probability).
Climate-change-induced loss of the state’s cultural heritage is a social justice issue that will be felt most acutely by low-income Illinois citizens and Tribal descendant communities who have traditionally been the most marginalized. Many live in the most vulnerable areas. Doing nothing in the face of this crisis is not only inaction. It is a conscious choice to let the tangible links to history disappear forever. Given the scale of this challenge, what is the best way forward?
If we are to change this state of affairs, we need more geospatial modeling and archaeological projects to locate sites to obtain a more realistic picture of what is threatened. Large-scale mitigation will require planning, funding, and archaeological work at an unprecedented scale. Annual spending in the United States on Cultural Resource Management (CRM) is currently $1.46 billion and is expected to grow to $1.85 billion by 2031. Even if we double or triple this number, the costs associated with such an effort would still only be a tiny fraction of state and federal budgets. While dealing with the hazard to the archaeological record posed by climate change seems impossible due to the scale of the problem, it is an attainable goal we could make real progress toward if we choose to prioritize it as a society. The cultural heritage of Illinois can, and should, be at the center of these discussions.