Location: Yuma County, at Bonny Lake State ParkSize: 50 acres.Designated: November, 1988Landowner: Bureau of Reclamation; leased by Colorado State Parks & Division of Wildlife
Bonny Prairie Natural Area supports a remnant of the loess prairie community, an ecosystem that may once have covered millions of acres in the central United States. Loess, the key element of this prairie, is a fine rock powder that results from the grinding of rocks beneath glaciers. When the ice sheet that covered much of North America eighteen thousand years ago melted, billions of tons of loess were exposed. Wind carried the loess to distant areas and, along with water, shaped the soft deposits into bluffs and rolling hills.
Loess deposits themselves are not rare; however, deep deposits and undisturbed areas with native vegetation are unusual. Because loess soils are fertile and easily tilled, this land was eagerly sought and cultivated as the midwest was settled. Extensive areas in Nebraska, Kansas and Iowa which formerly supported this community type are now devoted to the cultivation of corn and wheat. It is estimated that the little bluestem loess prairie community represented at Bonny Prairie now covers only about 35% or less of its former range. Although the community probably was once common in southeast Yuma and northeast Kit Carson counties, the prairie at Bonny Prairie Natural Area is one of the few fragments of remaining intact loess prairie known in Colorado today.
Upland loess prairies are typically dominated by warm-season grasses of medium height, especially little bluestem (Schizachyrium scoparium) and sideoats grama (Bouteloua curtipendula). The relatively lush and tall little bluestem prairie at Bonny stands in contrast to the sparse, sandy shortgrass prairie that dominates much of eastern Colorado.
Bonny Prairie was designated as a Colorado Natural Area in order to recognize and protect this unusual biological community and to provide a critical ecological baseline area for the loess region of the Great Plains. The site also supports one of Colorado's rarest plants, the prairie moonwort (Botrychium campestre).