The population of Bison bison was estimated to be around 30-60 million prior to the arrival of Europeans in North America. However, due to overhunting, habitat loss, and disease, their population was decimated to only a few hundred individuals by the late 1800s.
Conservation efforts were then initiated, and the population of Bison bison has since increased, but it is still significantly lower than it once was.According to the International Union for Conservation of Nature (IUCN), as of 2021, the total population of plains bison (Bison bison bison) is estimated to be around 31,000 individuals in North America. The population of wood bison (Bison bison athabascae) is estimated to be around 10,000 individuals in Canada and Alaska.
While the populations of both subspecies have increased from their historic lows, their numbers are still significantly lower than they were prior to European colonization. Therefore, the species Bison bison is classified as near threatened by the IUCN.