Wetlands are the most underappreciated of Illinois' ecosystems. Swamps, marshes, bogs, and other types of wetlands were long considered unattractive and a risk to human health. Many were drained to make way for farmland or urban development. The number of acres of wetlands fell from over eight million before European settlement to only 918,000 today. Of these, only 6,000 acres are of high quality and undisturbed.
In recent years, however, ecologists have touted the many benefits of wetlands, and their reputation has improved greatly. Wetlands filter and purify the water that flows through them, trapping sediments that would otherwise cloud our streams and river. Wetlands are nature's sponge, absorbing excess water from rain and snowmelt, and thus reducing the risk of flooding. Finally, wetlands slow the flow of water over land, keeping erosion in check.
Not least, wetlands are home to many of our most precious plants and animals. Fully 64% of the threatened and endangered species in Illinois as of 1993 use wetlands in some way, including 8 of the 9 threatened and endangered mammals, 30 of the 42 threatened and endangered birds, all five threatened and endangered amphibians, 9 of 13 threatened and endangered reptiles, and 12 of 30 fishes. Put differently, nearly one-fifth of all wetland species are considered threatened or endangered.