The advance of woodlands and agriculture have confined prairie communities to narrow ridges and steep hillsides. On the other hand, forests and agriculture brought with them new and varied species of wildlife. Species such as prairie chicken, prairie rattlesnake and plains pocket mouse have decreased while white-tail deer, raccoon, quail, pheasant, and wild turkey have flourished. The predominant plant communities on the forest are prairie and hardwood stands that contain species like bur oak, red oaks hickories, basswood, elms, ashes, Kentucky coffee tree, cottonwood, ironwood and red cedar. If one species was to be singled out as typical it would be bur oak due to its ability to grow on dry sites and withstand fire.
Black walnut is the most important and valuable commercial species.
The forest contains many areas of natural prairie comprised of big and little bluestem, indiangrass, sideoats grama and forbs such as yucca, pasque flower and lead plant. About 300 acres have been planted to red oak, black walnut, bur oak, green ash, white ash, poplar, shrubs and pine. The forest is named after the geological formation that reaches its fullest development only in western Iowa and in China . The Loess Hills are a unique formation and their existence and the fact that they have become vegetated with forest species in recent years played a role in the decision to develop a state forest in this area. Three of the Units, Mondamin, Pisgah and Little Sioux are named for towns in the vicinity.