Prairies are flatlands with plenty of short and tall grass. In North America, the prairies used to be populated with bison, lots of them. The bison are well suited for the prairies in several ways. The bison were hunted to almost extinction and replaced by ubiquitous cows, which eat through vegetation and causing overgrazing. Overgrazing and loss of bison harmed the health of the prairie, resulting to loss of biodiversity and loss of topsoil.