White River Badlands 43i. Keya Paha Tablelands 43j. Moreau Prairie 43k. It is a semiarid rolling plain of shale, siltstone, and sandstone punctuated by occasional buttes and badlands. Native grasslands persist in areas of steep or broken topography, but they have been largely replaced by spring wheat and alfalfa over most of the ecoregion.
Agriculture is limited by erratic precipitation patterns and limited opportunities for irrigation.
Rolling fields, native range, and rural hamlets characterize the Northwestern Great Plains. T he River Breaks form broken terraces and uplands that descend to the Missouri River and its major tributaries. They have formed particularly in soft, easily erodible strata, such as Pierre shale. The dissected topography, wooded draws, and uncultivated areas provide a haven for wildlife. Riparian gallery forests of cottonwood and green ash persist along major tributaries such as the Moreau and Cheyenne rivers, but they have largely been eliminated along the Missouri River by impoundments.