Learn More About Ridgetop Hill Prairie

Landscape and Stewardship

Hill prairies are an extremely rare habitat in Illinois that are still being lost to development, woodland invasion, and erosion.  The Illinois Department of Natural Resources estimates that only about 500 acres of high-quality hill prairie remains in the state with about half comprised of less than one contiguous acre.  The location of Ridgetop Hill Prairie is even more rare since most in Illinois are restricted to the much larger Mississippi and Illinois river corridors.  Only four known high-quality hill prairies remain along the Mackinaw River, two of which are owned by ParkLands – Ridgetop and a section of the Merwin Preserve.  The other two are privately owned.

Thus, the Ridgetop Hill Prairie was awarded the perpetual protections of an Illinois Nature Preserve designation in June of 1984, making it only the second Nature Preserve in Woodford county.

The goal of the Illinois Nature Preserves Commission is to permanently protect the less than 0.1% of our state’s landscape that exists as it did before European settlement.  While several ParkLands properties are protected as an Illinois Land and Water Reserve, the Nature Preserve designation is saved for the state’s rarest plants, animals, and natural land features.  As summarized from the Nature Preserves Commission’s examination of the Ridgetop Hill Prairie Preserve:

“Ridgetop Hill Prairie contains glacial drift hill prairies and forest communities once abundant in the Grand Prairie Section of the Grand Prairie Natural Division. The prairie supports over 40 species of plants and is dominated by little bluestem and side oats grama. Typical prairie forbs include aromatic aster, purple prairie clover and goldenrods.

The prairie opening on the long narrow ridge closest to the river is richest in composition. The dry-mesic upland forest, occupying about 10 acres, is dominated by white oak, shagbark hickory and ironwood.

The preserve, although small, has a great diversity of habitats that support typical animal species found in upland forest, forest edge, brush, bottomland and river bank areas. Of particular interest are migrating hawks and nesting lark sparrows on nearby properties.”

The glacial drift hill prairie occurs in four separate areas on steep, well-drained, southwest facing slopes above the river and its tributary ravines, occupying about 3 acres of this site in all.  The slope is that of the Eureka end moraine created during the most recent (Wisconsinan) glacial period 15-20,000 years ago.  Just how high is the ridge of Ridgetop?  There is 110 feet of relief from the prairie to the river below.

The rarity and small scale of this remnant necessitates intense management that includes prescribed fire, removing woody vegetation, and exotic species control.  Honey suckle, autumn olive, sweet clover, and bird’s-foot trefoil have been a focus of recent management.

Somewhat counterintuitively, several native trees pose a serious threat to the hill prairies.  Lack of natural fire has allowed cedars, sugar maples, and other species to thrive, blocking direct light to the prairie.  When this happens, prairie forbs thin, erosion of the light sandy soil ensues, and the priceless seedbank washes downhill into the river.  Planting trees is a key part of our restorations elsewhere, but here it can mean losing the remnant forever.

Unique to this dry, sloping habitat is an uncommon concentration of chinquapin oaks.  The dry mesic upland forest has also undergone a lot of management, primarily cutting mesic species like sugar maple and black cherry.  This promotes a more diverse herbaceous layer that has included bottlebrush grass and purple milkweed.

This preserve represents the first of several joint efforts between Parklands and The Nature Conservancy.  In early 1982, the organizations finalized a plan through which the Nature Conservancy would purchase the property and later convey ownership to ParkLands once adequate funds were raised.  ParkLands took full ownership in 1988.  The significance and urgency of these decisions are told by Mark Wyman in his history of the ParkLands Foundation:

“The Ridgetop Prairie had been spotted during an inventory of undisturbed prairie and forest areas, part of a state-federal survey conducted by the Illinois Department of Conservation, the Illinois Natural History Survey, and the University of Illinois.  The prairie was part of the newly platted Tall Oaks Subdivision, and buyers were already snapping up nearby lots, further goading conservationists to act to save the high-quality glacial drift hill prairie.  Because of its undulating topography with steep ravines, it had never been plowed and was called one of the best examples of hilltop prairie in Central Illinois.”

“Ridgetop Prairie carried ParkLands into new territory not only in a geographical sense.  Earlier tracts had usually been acquired because they were forested areas that could easily accommodate visitors on trails for low-intensity use.  The Ridgetop Prairie, however, ‘marked the first time we bought land strictly for its environmental qualities,’ noted Dale Birkenholz.  Ridgetop’s relatively inaccessible location and lack of trails meant that it would probably never become a popular spot for hikers; instead, the new preserve would be nurtured for its values as a prairie, with at least 42 species of prairie plant initially, including mountain mint, coneflowers, little bluestem grass, and sideoats grama.”

The ParkLands Foundation manages two other Illinois Nature Preserves, both in McLean County; the Weston Cemetery Prairie Nature Preserve and a section of the Merwin Preserve, which also contains a hill prairie on the south-facing slopes of the Mackinaw River.