Corridors for Tomorrow


The first European settlers to arrive in Illinois encountered a fabulous natural landscape. The northern part of the state was a mosaic of many prairies types, wetlands, forests, and savannahs. Along the magnificent natural shoreline of Lake Michigan were beaches, sand dunes, swales, and cliffs dissected by wooded ravines. The central part of Illinois was primarily tall grass prairie, spectacular at all seasons, dotted with isolated woods known as prairie groves. Towards the west and south the prairies gave way to mature forests and tall cliffs of sandstone and limestone. Occurring at the extreme southern part of the state were swamps filled with giant bald cypress and tupelo trees, reminiscent of a much farther south and lacking only Spanish moss and alligators. What a sight this original and wild Illinois must have been!

The ecological diversity of Illinois is reflected in the large number of native species of plants and animals. A recent compilation by Sue Post of the Illinois Natural History Survey estimates there are over 54,000 species of organisms native to Illinois, including 2,574 plants, 20,000 fungi, 28,000 insects and relatives, 374 mollusks, 187 fishes, 39 amphibians, 59 reptiles, 297 birds, and 67 mammals.

The rapid settlement and subsequent economic development of Illinois has dramatically effected the biology of Illinois. Most of this development has been based on the conversion of original native habitat to agricultural fields and areas for industry and urban development. Logging, mining, and pollution have degraded the remaining natural habitats. Regrettably, only a tiny fraction of the original prairies, forests, savannahs, and wetlands have survived. In this regard we rank 49th among states (Iowa is 50th).

This loss of habitat has been responsible not only for the extinction of some species, but also for a drastic reduction in the abundance of most native species. Currently, there are 497 species listed as endangered, mostly plants and conspicuous animals, and it is estimated that at least 115 species have been lost from the state.

With funding from the Illinois Environmental Protection Fund Commission, the Natural History Survey is investigating ways that the extensive Illinois highway corridor system can provide habit for the species that comprise the rich native biodiversity of Illinois. This project is entitled Corridors for Tomorrow. The Illinois Interstate highway system is the third largest in the nation, with about 1,900 miles of corridors, 370 interchanges, and 31 open or proposed rest areas. Associated with this system is about 135,000 acres of land. These corridors are in state ownership and are subject to far less pressure from economic and ownership changes than most land in the state.

Following traditional highway management practices, most right-of-way is currently planted with species not native to Illinois or even the United States. Management practices have also emphasized cyclic patterns of disturbance, such as herbicide use and mowing. As economic restrictions have recently limited this management, and to reflect the public's growing awareness with the environment, we must reevaluate approaches to roadside design. One alternative is to use highway right-of-ways to provide much needed habitat for the plants, birds, mammals, and insects that are part of our state's natural heritage.

Each unit in the Interstate highway system -- corridors, interchanges, and rest areas -- have opportunities for the effective use of these native plant communities. The long expanses of corridors can be used for prairie grasses, more complete prairie reconstructions, designed interpretations of prairie, mass plantings of native shrubs, and scattered, clustered or dense stands of native trees. Interchanges present excellent opportunities for the use of native plants because of their relative isolation and large size. The extensive space at interchanges will allow better development of prairies, mixed shrubs and trees, simulated woodlands, and savannahs. These added habitats offer our native plants and animals structural cover, reproductive sites, and food resources.

Revegetation will increase the average size of our habitat fragments, and decrease habitat isolation by providing connecting corridors. The importance of highways as dispersal routes connecting habitat fragments has been demonstrated for small mammals. Prairie plantings would provide habitat for many grassland birds, wintering ground for upland gamebirds, and a seed source for migrating birds. Native trees and shrubs would also provide additional foraging habitat for breeding birds in nearby forest and important stop-over points for migrating birds. Numerous prairie plants will provide pollen, nectar and food resources for native bees, wasps, butterflies and other insects. The overall design of highway plantings needs careful consideration including species that cover the complete range of flowering period, from early spring to late fall, with a broad fruiting period. Plants are largely dependent on insects for pollination and on a wide variety of animals for seed dispersal. A phenologically complete habitat provides optimum conditions for the greatest diversity of native insects, birds, and small mammals.

As part of Corridors for Tomorrow , we developed plans to construct perches for raptor birds to place along highway corridors. During the course of this project we placed about 20 of these along selected Interstate highways in Illinois.

Native plant species hold enormous potential for landscape design. Plants form the aesthetic element observed by motorists, and they provide habitat building blocks for animals. While the ultimate goal of Corridors for Tomorrow is to recreate or at least simulate naturally occurring habitats, it will be necessary to use landscape design to adapt to the conditions found along right-of-ways. Although biologists can determine the kinds of habitats they want to recreate, they generally do not have the expertise to develop and complete landscaping plans and specifications. Collaborating with this aspect of Corridors for Tomorrow are Terence Harkness, a faculty member of the Department of Landscape Architecture of the University of Illinois, Matt Torgerson, a graduate student in Landscape Architecture, and Tom Brooks of the Survey.

Landscape designs are being developed to provide better interpretations of biodiversity to the motorist than would strict recreation of native habitats. For example, a realistic prairie restoration 30' wide is not very dramatic at 65 miles per hour. A way to help interpret prairies for the motorist is to dissect it and show the component parts on a large scale. The components could be presented in mass plantings of showy species at intervals along the corridors. This presentation would provide an attractive public educational opportunity.

Perhaps the most practical human benefit from revegetation efforts in Illinois will be the improvement of our quality of environment. We are all concerned about how human activities are modifying the very nature of our world. Climatic changes, toxic pollution, erosion, diminishing water quality, food shortage, and depletion of our non-renewable energy resources affect everyone's life. Diverse highway corridors act as buffers between agricultural and urban development and the existing native habitats of Illinois. These revegetation buffers soak up pollution, capture and store carbon dioxide, filter and dilute dust and exhaust pollution, retard erosion and loss of top soil, and prevent siltation of our stream, rivers and lakes. Reduced maintenance practices, including mowing and herbicide application, will significantly reduce our State's use of energy and toxic chemicals. Highway landscaping with native species also contributes to the scenic beauty of Illinois and leaves motorists with a favorable, if not nostalgic image. An Illinois revegetation program will help activate local interest in environmental issues and stimulate grassroot efforts for and environmentally sound Illinois.

Click here for published references consulted for this project.

Return to Ken Robertson's homepage