Prairies are characterized by a lack of trees and tall shrubs and are dominated by grasses, sedges and forbs. They occur on a wide variety of topography, soil types and moisture regimes - from wet silty clay to the driest sandy soils.
Prairies are located mostly in the southern and western parts of the state and are divided into six different types. Over 400 species of native vascular plants are characteristic of Wisconsin prairies, and most are restricted to prairie and savanna community types. In addition to a varied plant community, prairies have a diverse and specialized fauna, especially among prairie invertebrates, prairie and grassland herptiles and grassland birds.
Surrogate grasslands, such as agricultural hayfields, small grains, pastures, fallow fields, and cool season grass fields provide important habitat for many birds and some reptiles, and are treated under "Anthropogenic Habitats".
Tallgrass prairies are among the most decimated and threatened natural communities in the Midwest and the world. Of the 2.1 million acres (6% of state land area) that were native prairie when Europeans arrived 150 years ago, less than 10,000 acres of varying quality (<1 % of state land area) native prairie remains today. Most native prairies found today in Wisconsin are small remnants that are less than 10 acres in size. Very few exceed 50 acres, too small to support a full complement of species that typically inhabit a native prairie ecosystem. Most of the prairies left today are either of the wet or dry types. Mesic prairie, which was the most common type in pre-settlement days, is almost gone now, with only about 100 acres known to exist today.
Historically, prairies were maintained primarily by frequent fires, either started by lightning strikes or by Native Americans who burned large areas to produce food for game or to aid in hunting and gathering activities. On most soil types and moisture regimes in Wisconsin's climate, grasslands in the absence of fire, mowing or grazing will succeed to woody species over time.