Rebuilding Natural Ecosystems

April 10, 1991

A pair of "green thumb" projects near Chicago bear lessons for restoring the environment.

One effort, by the Nature Conservancy, seeks to rebuild the savannah ecology that existed on a 90-acre tract before settlement destroyed it. Savannahs -- grassy vistas broken by scattered oaks -- differ from forests in their smaller number of trees. They differ from the prairies usually associated with the Great Plains by their distinctive plant and animal species. The conservancy group first tried to resurrect a prairie on the land after burning off non-native vegetation. This fizzled, but new neighbors moved in: thistles, cream gentians and yellow pimpernels, thriving in the partial shade of the oaks that had made it so hard for prairie plants.

The Nature Conservancy searched old records to learn what plants lived on the Illinois savannah before civilization arrived. Identifying 100 "associated" species, the group harvested seeds from surviving members in odd places such as railroad rights-of-way and old cemeteries. After replanting, the naturalists were pleased and surprised to find uncommon species of butterflies and birds, including a pair of Eastern bluebirds, moving in.

A bigger rebuilding effort, on a 1,000-acre expanse inside the 4-mile storage ring of the Fermi National Accelerator Laboratory recreated a prairie environment that supports 125 native plant species. The experiment proceeded slowly until "matrix" species, mostly tall grasses, established themselves and changed soil chemistry. Then, in stages, other species surfaced. Meadowlarks, falcons, bobolinks, coyotes and foxes have now arrived.

While theoretical ecologists still have not accepted all the expansive claims made by the preservationists, the message for those seeking to restore a natural balance badly shaken by centuries of human expansion in the Chesapeake Bay or other Eastern waterways is that experimentation is a key feature of scientific discovery.

Attempts to restore or make new wetlands or even offshore reefs, for instance, have met with limited success. Using the Illinois model, that may simply mean the right mix of "matrix" species has not yet been introduced, or that it takes longer to rebuild ecosystems than to destroy them.

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