Ranging from Mississippi through southern Illinois, this ecoregion includes the incredibly diverse Tunica Hills region of Louisiana and Mississippi.
The soil, wind-deposited silt called loess, is up to 200 feet deep. The silt and underlying soils are easily eroded by wind or rain, leaving sculpted ridges and slopes. The cool ravines of the Tunica Hills have produced a micro-climate, home to plants and animals typically found in northerly regions such as the Ozarks and Appalachian Mountains. The forests in the area are the most species-rich of all southern forests.
Despite extensive ridge-top clearing in the early- to mid-1800s, it is believed that nearly all the plant and animal species originally found in the area still exist. Following the Civil War, many of the area's plantations were abandoned, and natural succession allowed the area to recover from previous disturbances.
The Tunica Hills support the threatened Louisiana black bear, the only known Louisiana location of wild ginseng, and Canada wild ginger. Uncommon animals such as timber rattlesnakes and migratory birds such as the yellow-billed cuckoo, wood thrush and great-crested flycatcher exist in significant numbers in the Tunica Hills while their numbers are decreasing elsewhere.