A thousand years ago a succession of prehistoric peoples found an ideal habitat in the Illinois River valley below Peoria. Five miles wide in places, the valley was the site of a series of town centers scattered up and down its 100 miles. Remnants of this extensive and long-lived occupation are everywhere. By 1980 archaeologists had found evidence in Fulton County alone of roughly 3,000 village and burial sites, representing all the known eras of Native American culture in Illinois.
Later Illinoisans also found the river a rich resource. From 1905 to 1915, more freshwater fish wereharvested from the Illinois River than from any other such river in the U.S., except for the Columbia River in Washington state. In 1908 alone, nearly 25 million pounds of fish were harvested. In 1950, flocks of migrating mallards and lesser scaup ducks numbered two million along the Illinois, making it a hunter's paradise. Just after the turn of the present century, the Illinois briefly sustained a fleet of 2,600 boats harvesting mussels for the booming pearl button industry.
Today's hunters and commercial fishermen cannot match those historic harvests. The long-term sustainability of the river's biological harvest was hampered by a succession of ecological injuries. They include:
* Drainage of wetlands and the channelization of tributaries that began in the late 1800s. These changes sped up the rate at which water entered the Illinois River, enhancing its ability to carry off topsoil and pollutants from the land into the river.
* Diversion of Chicago sewage and factory
pollution into the river beginning in 1900. Extra flows raised water levels, killing less tolerant trees in the floodplain; excessive nutrients degraded water quality.
* Draining wetlands and leveeing of half the floodplain from 1903 to 1926. Undertaken mainly for agriculture, these projects eliminated the most productive habitat and reduced the system's ability to hold and store water.
* Construction and maintenance of a nine-foot minimum navigation channel. Finished in the 1930s, the dam system permanently inundated parts of the floodplain accustomed to seasonal wetting and drying; year-round sedimentation is primarily responsible for the reduction of floodplain lakes to shallow, featureless "deserts" of soft mud.
*More intensive, chemical-reliant farming, especially since the late 1940s. Industrial-style farming increased soil loss and contamination by farm chemicals, especially fertilizers.
There are signs of improvement in the Illinois' chemical water quality, although long-lived pollutants such as heavy metals still linger in bottom sediments. The physical changes, however, are responsible for doing the most enduring damage to the Illinois River's once-fabled abundance. For example, boat traffic--made possible by the deeper channel--generates bank-eroding waves and keeps sediments suspended, clouding river water. Such changes risk sacrificing this once-diverse resource to a single-function stream that serves primarily to transport bulk cargoes by barge.
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