Before and After Bison Research Illuminates a Surprisingly Subtle Impact

Bison had been missing from Illinois prairies for 140 years when they were reintroduced to Nachusa Grasslands in 2014. The change returned an iconic species to the tallgrass prairie landscape it once roamed, and provided an opportunity to study the ways bison affect their habitat. To date, TNC staff and partners have released more than 15 scientific papers on the topic. Dr. Elizabeth Bach, the ecosystem research scientist at Nachusa Grasslands, shares what researchers are learning and why it matters.

What makes the reintroduction of bison at Nachusa unique?

This is the first time the species was introduced as a conservation herd east of the Mississippi River. In reintroductions in the west, the grasslands were mostly intact. At Nachusa, they are quite recently restored. We have lots of questions about how this re-created landscape—and its component plants, insects, birds and other species—are responding to the presence of bison.

Why are we studying the bison, and why is it important to publish that research in scientific journals?

Ecology is the study of the relationships among living organisms and with their physical environment, and that’s exactly what we’re exploring. We know bison have an outsize role in shaping diversity; yet, because bison haven’t been in the Illinois region for a long time, there are no data about their role here. Sharing our work with the scientific community expands knowledge about how tallgrass prairie ecosystems function. Publishing also holds us accountable to our goal of restoring the ecology at Nachusa.

What are the common threads of the existing studies? What are we learning?

My job is to look at what’s happening with all the plants and animals, how management and restoration practices affect the whole ecosystem and how communities of species and those practices interact. In contrast with what we hypothesized, our studies show that few of the insects, plants, small mammals or birds seem impacted by the bison. It’s harmonious, not negative or positive. Except for now-thriving populations of dung beetles, because there’s a lot more poop on the landscape! We also learned that what we thought were generalizable patterns about North American tallgrass prairies may not be. Nachusa is very different from a place like Kansas, which had a huge ecological response in the first five years after bison reintroductions. So perhaps our grasslands were already productive because we’d been managing them so intensively. Or maybe we will see differences, but not for 10 or 15 years. That’s why we’ll keep inviting scientists, as well as deepening partnerships with Indigenous communities and others, to advance research at Nachusa.