The vegetation types of Marion County, Illinois prior to European settlement, which were derived from soil association surveys, were compared to a satellite map of current vegetation types to quantify their change over time. GIS analysis indicates that 10% of presettlement prairie is currently grassland, 2% of presettlement prairie has been converted to forest, 32% of original prairie has been converted to agriculture and urban use, 17% of presettlement forest remains intact, grassland comprises 18% of presettlement forest while 21% of presettlement forest has been converted to agricultural and urban use.
Unger, Daniel, "Comparison of Presettlement and Present Vegetation Cover of Marion County, Illinois using a Geographic Information System" (1998). Faculty Presentations. Paper 23.