Illinois Natural History Survey - University of Illinois

The Tallgrass Prairie in Illinois


What is a Prairie?

Prairies are a type of grassland, a landscape dominated by herbaceous plants, especially grasses; trees are either absent or only widely scattered on the landscape. Grasslands occur in many regions, such as the llanos of Venezuela, the pampas of Argentina, the cerrado and campos of Brazil, the steppes of central Asia, the veldt and savannas of Africa, and the grasslands of Australia. Approximately 32 to 40% of the world's land surface is, or was, covered by grasslands. Today, grasslands are extremely important for agriculture, and approximately 70% of the food produced for humans comes from these regions.

Grasslands are the largest vegetation type in North America, covering approximately 15% of the land area. Prairies are the grasslands found in the central part of the North American continent. They form a more or less continuous, roughly triangular area that extends for about 2,400 miles (3,870 km) from Alberta, Saskatchewan, and Manitoba southward through the Great Plains to southern Texas and adjacent Mexico and approximately 1,000 miles (1,612 km) from western Indiana westward to the foothills of the Rocky Mountains, covering 1.4 million square miles. Rainfall decreases from east to west, resulting in different types of prairies, with the tallgrass prairie in the wetter eastern region, mixed-grass prairie in the central Great Plains, and shortgrass prairie towards the rain shadow of the Rockies. Today, these three prairie types largely correspond to the corn/soybean area, the wheat belt, and the western rangelands, respectively.

Illinois lies within an area called the "prairie peninsula," an eastward extension of prairies that borders deciduous forests to the north, east, and south. This is part of the tallgrass prairie region, sometimes called the true prairie, with the landscape dominated by grasses such as big bluestem and Indian grass as well as a large number of other species of grasses and wildflowers, the latter called forbs. The vegetation sometimes reaches a height of 10 feet or more.

The first European settlers moving westward from the forests of the eastern United States encountered the prairies, which seemed like a vast ocean of grass. The wind caused waves on the surface of the shimmering grasses. One type of wagon used by the pioneers was the "prairie schooner," a reference to a sailing vessel, further adding to the analogy of the prairie being a large inland sea of grasses. It was easy to get lost in the prairie, especially since there were few trees or other natural features to act as landmarks. Even when on horseback, it was often not possible to see across the prairie to the horizon.

Introduction    > Formation of Prairies

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