Northwest Illinois Forest

The rugged landscape of northwestern Illinois shows the effects of millions of years of erosion. The bedrock was carved and cut down by rivers and streams. This region, known as the Wisconsin Driftless Division, was bypassed by the most recent glaciers. Recent studies suggest that calving of glacial ice in deep Lake Superior prevented the glacier from moving south into the driftless area. Unusual habitats support unusual plant and animal communities. Several of the plants and animals living here, such as the paper birch (Betula papyrifera) and the Pleistocene disc snail (Discus macclintocki), seem separated from their typical ranges farther to the north. These plants and animals live on the cool, damp, north-facing slopes of the bedrock exposures typical of this area. In this special habitat they find what is needed for their survival. These conditions are not present in the surrounding flatlands of the glaciated areas.