In the precolonial landscape, tall grass prairies were a dominant plant community in much of eastern North America. Fire was utilized by Indigenous peoples to maintain these grasslands, along with other varieties of grasslands, savannahs and oak woodlands. In precolonial Wisconsin, there was an estimated 800,000 acres of mesic tall grass prairie, mostly in the southern part of the state. Now only 100 acres of these historic grasslands persist on today’s landscape.
Mesic prairies, meaning prairies with moderate amounts of moisture, often had deep, rich soil. These soils were built over millenia. The root systems of tall grass prairie plants can reach incredible depths, with grass species like big bluestem (Andropogon gerardii) and switchgrass (Panicum virgatum) reaching upwards of 10 feet, while long-lived wildflowers like compass plant (Silphium laciniatum) and prairie dock (Silphium terebinthinaceum) have taproots that can reach down 15 feet.
Over time, these plants would die and their root systems would break down in the soil, sequestering carbon deep within the soil and further enriching them for the next generation of prairie plants. Over the course of a few years, surface plant material would build up into a thick thatch. This thatch provided fuel to carry fire across the landscape. These fires further enriched the prairie by returning important nutrients back to the soil while also exposing its surface where new seedlings could germinate and develop.
Rich soils with little trees to remove were ideal candidates for conversion to agricultural fields.
Many, but not all, of the places that were not directly converted to agriculture or developed were left unmanaged. The suppression of fire on the landscape allowed woody succession to occur, further displacing grassland species. Plants and animals that relied on regular disturbance and high quality, diverse and open grasslands were pushed into smaller and smaller areas, or in some instances completely extirpated from an area.
Ironically, one place where land use changed but inadvertently maintained grassland elements was railroad right-of-ways. The once rich tapestry of grasses and wildflowers where the farm fields now stand found refuge along the wayside of tracks. As locomotives passed by, the occasional spark would ignite built up thatch along these corridors. These accidental prairies are a remnant of what large areas of southern Wisconsin may have once looked.
Over the last few decades, many of these railroads have become defunct. Some have been converted into pedestrian bikepaths, excellent for outdoor recreation. The majority of these prairie remnants, however, have now been lost to woody succession due to a lack of disturbance. Without intentional management through prescribed fire (or mowing), shrubs and trees and an ever-expanding array of invasive species have crept in to replace them.
There are, however, still a few places hanging on, some of which are protected and designated as State Natural Areas (SNA) by the Wisconsin Department of Natural Resources. Oakfield Railroad Prairie SNA and Koro Railroad Prairie SNA are two such places in Fond du Lac and Winnebago Counties, respectively.
Thankfully there are many people now interested and passionate about natural spaces, prairie plants, pollinators and creating new habitats for these species to thrive. Prairie remnants are an important part of this landscape’s natural history and can serve as teachers and templates for those interested in restoring mesic prairies to the landscape. We should continue to protect, advocate for and manage them in perpetuity.
