Urbanization and commercial development have taken their toll on the plant and animal resources of Illinois. Northern and central Illinois once supported typical prairie flora, but nearly all the land has been given over to crops, roads, and suburban lawns. About 90% of the oak and hickory forests that once were common in the north have been cut down for fuel and lumber. In the forests that do remain, mostly in the south, typical trees are black oak, sugar maple, box elder, slippery elm, beech, shagbark hickory, white ash, sycamore, black walnut, sweet gum, cottonwood, black willow, and jack pine. Characteristic wildflowers are the Chase aster, French's shooting star, lupine, primrose violet, purple trillium, small fringed gentian, and yellow fringed orchid. The leafy prairie-clover was listed as endangered in 2003; small-whorled pogonia, lakeside daisy, prairie bush-clover, and eastern prairie fringed orchid are among seven threatened plant species that year.
Before 1800, wildlife was abundant on the prairies, but the bison, elk, bear, and wolves that once roamed freely have long since vanished. The white-tailed deer (the state animal) disappeared in 1910 but was successfully reintroduced in 1933 by the Department of Conservation. Among the state's fur-bearing mammals are opossum, raccoon, mink, red and gray foxes, and muskrat. More than 350 birds have been identified, with such game birds as ruffed grouse, wild turkey, and bobwhite quail especially prized. Other indigenous birds are the cardinal (the state bird), horned lark, blue jay, purple martin, black-capped chickadee, tufted titmouse, bluebird, cedar waxwing, great crested flycatcher, and yellow-shafted flicker. Mallard and black ducks are common, and several subspecies of Canada goose are also found. The state claims 17 types of native turtle, 46 kinds of snake, 19 varieties of salamander, and 21 types of frog and toad. Heavy industrial and sewage pollution have eliminated most native fish, except for the durable carp and catfish. Coho salmon were introduced into Lake Michigan in the 1960s, thus reviving sport fishing.
In 1973, the Department of Conservation established an endangered and threatened species protection program. In 2003, the US Fish and Wildlife Service listed 19 Illinois animal species as endangered or threatened. Included among threatened animals are the bald eagle and gray wolf. Endangered species include the piping plover, pallid sturgeon, Hine's emerald dragonfly, Higgins' eye pearly mussel, and the least tern.