Before the prairies were converted to farmland, great fires sparked by lightning or by Native American hunting parties would sweep across the landscape, hindered only by the occasional river or lake. Shortly after the fires, the grasses would begin to emerge and quickly grow to heights of six feet or more. Today, the use of fire is an important management tool for maintaining the health of a native prairie. Fire stimulates the growth of many native grasses and wildflowers. Since most prairie plants grow best in warm soil, the use of fire can effectively lengthen the growing season for native warm-season plants.
Fire is very effective at controlling the invasion of woody shrubs and trees.
This significantly reduces the need to use chemical herbicides. Fire can also act as a fertilizer by releasing nitrogen from the previous year's plant matter into the soil. When used properly under the right conditions, fire is a cost effective, quick, and environmentally sound method for maintaining a healthy prairie ecosystem. In Thomas Lake Park, fire is used to assist in the removal of unwanted species and to help recycle nutrients into the soil. The Eagan Forestry Division, together with the Eagan Fire Department, conduct controlled, prescribed burns of the grasses in the spring.