Ecosystem Map from the Morton Arboretum

Looking at the ecosystem map, you will notice that most wooded areas are east of the river and most prairies are west. This trend relates to the critical role of the river in preventing wildfires from spreading. Prairie fires started from lightening strikes or by deliberate fires set by Native Americans. The fires then spread east with prevailing winds. When fires reached the river, they died out. Forest plants and trees, such as maples, willows, and basswood, were able to survive.

Courtesy of Jeanette McBride–Morton Arboretum.

Nature's Mosaic

The Chicago River watershed sits on an ecological transition zone between western prairies and eastern forests. This zone was once a mosaic of tallgrass prairies, wooded areas, and wetlands. The driving force behind this diverse ecosystem was wildfires. The intensity and frequency of the fires depended on the amount of soil moisture, which in turn determined what vegetation would develop and thrive.

Three hundred and fifty years ago, the vegetation was diverse, and the area teemed with wildlife. Many factors, such as population growth, habitat loss, fire suppression, and invasive species, have vastly changed this landscape.

Ecosystem Map from the Morton Arboretum

Nature's Mosaic