Building Biodiversity

The Restoration of Swallow Cliff Woods

Fire and ice created the landscape of Swallow Cliff Woods. The glaciers retreated north about 12,000 years ago, leaving behind a varied landscape of morainal hills and pothole lakes and marshes. Meltwater from the ice scoured out the Sag Valley whose steep southern wall forms the Swallow "Cliffs".

The fires started sometime after the ice left. Some fires were started by lightning, some by Native Americans who used fire to drive animals in the hunt and to improve forage for big grazing animals like bison and elk.

Driven by the wind and shaped by the terrain, fires swept into Swallow Cliff from the southwest. On level land like the southern end of Swallow Cliff Woods, grass fires would burn with ferocious intensity. Trees and shrubs had a difficult time invading the resulting lush prairies. Where streams had cut valleys into the landscape, the steep slopes formed obstacles to the fires. Less intense ground fires permitted other plant communities, including a variety of woodlands, to develop and flourish.

Swallow Cliff Woods became a landscape shaped by fire. From south to north, the flowery meadows of the tall grass prairies gave way to sunny groves of white and bur oak, then to denser woodlands of red oak. In the cool, moist ravines, forest of sugar maple and basswood flourished. The wetlands hosted marsh plants and sedge meadows. Each of these natural plant communities supported its own distinctive group of animals.

Many Native Americans used Swallow Cliff Woods seasonally for hunting and gathering, and as a place to take shelter from the long winters. More recently, settlers took timber from the woodlands and hay from the prairies. They hunted here, and grazed cattle on the native grasses.

Ecological Restoration

In recent decades, the natural biodiversity of Swallow Cliff Woods has been threatened by the suppression of fire and by the invasion of exotic plants, especially shrubs such as buckthorn and smooth arrow-wood. These shrubs form dense thickets, whose deep shade prevents native plants from reproducing. Eventually, even the oaks will be lost because the brush prevents the growth of new generations of trees.

Restoration at Swallow Cliff Woods is helping to reestablish the ecological forces that created the natural biodiversity. By removing invading exotics, reintroducing native plants, and bringing back fire, the beauty and variety of our native landscape will be enjoyed by future generations.

The Swallow Cliff Woods restoration project is the largest ever undertaken by the Forest Preserve District in some 30 years of restoration work. It is a cooperative project whose partners include the USDA Forest Service, USDA Natural Resources Conservation Service, the Illinois Department of Natural Resources, The Nature Conservancy, and the USDI Fish and Wildlife Service.

Interpretive Trails

Enjoy a pleasant walk along the loop trail shown on the map below. Print this page and bring it with you, to help interpret what you see along the way. The numbers in the descriptions that follow are keyed to the numbers on the map. Start your walk by following the trail immediately across the drive from the small stone shelter. The total walking time on this easy trail is less than an hour. Please stay on the main trails, since traffic on small side trails creates serious erosion problems.

1. Heading south from the parking lot, the trail is bordered by dense shrubs and small trees. Fire suppression allowed these to invade areas that were once prairie. The shade cast by these shrubs, mostly smooth arrow-wood, prevent the growth of wildflowers and grasses.

2. Where the trail forks, turn right and enter a large area under restoration. The big bur and white oaks around you grew for more than 200 years in an open setting. The low, broad crowns of the trees tell us that this was open ground when these trees were young. The large horizontal branches mean the area remained open for a long time. Restoration crews have removed the dense shrub growth that resulted from fire suppression and have sown the seeds of native plants. The open oak grove community will take several years to restore. Seeding will continue until the wildflowers, grasses, and sedges are well established.

3. Civilian Conseration Corps workers built this trailside shelter during the Great Depression. The marvelous view from this hilltop includes three marshes. Each was partially drained before the District bought the land. With the assistance of its partners, the District plans to restore the historical water levels. The brushy areas to the south of the largest marshes will be restored to prairie.

4. Walking north from the shelter, you pass from the open groves into a much denser woodland of red oak and hickory. Non-native exotic species have been removed, but many shrubs remain. These shrubs are mainly native hawthorns and hazels. Both provide food and shelter for wildlife. Note the tall, narrow crowns of the big trees. This shows us that the area was already a dense woodland when these trees began to grow.

Turn right at the trail junction. After you walk another few hundred feet, you will see a wide gravel lane leading to the left. This lane leads to the toboggan lsides. As you walk the lane you will see the transition from oak woods to maple forest.

5. Note the deep ravines harboring shade tolerant, fire sensitive trees such as sugar maple and basswood. The restoration of Swallow Cliff Woods is restoring the dynamic interface between all these many communities and provides visitors with a glimpse of the past.

Swallow Cliff Woods is an 800 acre Forest Preserve located at the southwest corner of Route 83 and U.S. 45, Palos Park. The parking lot and trailhead are off U.S. 45 near 119th Street. For more information about Swallow Cliff Woods or other Cook County Forest Preserves, please call 1-800-870-3666.

Swallow Cliff Woods Ecosystem Restoration Demonstration Project

a joint project of

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