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"There are prairies three, six, ten, and twenty leagues [one league is three miles] in length, and three in width, surrounded by forests of the same extent; beyond these the prairies begin again, so that there is as much of one sort of land as of the other."The tallgrass prairie ecosystem that once stretched from the Great Plains to the Midwest (western Iowa through Illinois to western Indiana) is part of the Prairie Peninsula. Illinois, Iowa and Missouri are completely included in this unique biome. This area is best known for its tallgrass prairies. This wedge shaped area has characteristics that make it unique.
-from Paul M. Angle's Prairie State
 Click on map to enlarge |
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The Prairie Peninsula is a wedge of prairie that extends from western Iowa to western Indiana. |
The Prairie Peninsula has been studied for many years. One of the questions puzzling researchers was why this region of the United States supported grasslands. Annual precipitation is high enough to support forest, but grasslands existed nevertheless. Prairie expanded across Illinois during a long, dry period.
One of the answers was found to be in prairie fires. Frequent prairie fires slowed down invasion by forest. Annual dry periods in autumn and early spring, periodic droughts, and the level shape of the land all act to promote the spread of fire. In addition, prairie vegetation becomes extremely flammable every fall, which encourages widespread fires.
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Copyright © 2000 Illinois State Museum
