Tallgrass prairie once covered 170 million acres of North America, but within a generation, most of it had been transformed into farmland. Today less than 4% remains intact, mostly in the Kansas Flint Hills. The tallgrass prairie is an ecosystem native to central North America capable of supporting significant biodiversity. Parts of the ecoregion are among the "top ten ecoregions for reptiles, birds, butterflies, and tree species.