From The Conversation (Matthew D. Moran):
It was not always certain that bison could rebound. Once numbering in the tens of millions, they dominated the Great Plains landscape until the late 1800s, anchoring a remarkable ecosystem that contained perhaps the greatest concentration of mammals on Earth. That abundance was wiped out as settlers and the U.S. government engaged in a brutally effective campaign to eradicate the ecosystem and the native cultures that relied on it.
Bison were shot by the millions, sometimes for “sport,” sometimes for profit, and ultimately to deprive Native Americans of vital resources. By 1890 fewer than 1,000 bison were left, and the outlook for them was bleak. Two small wild populations remained, in Yellowstone National Park and northern Alberta, Canada; and a few individuals survived in zoos and on private ranches.
Remarkably, a movement developed to save the bison and ultimately became a conservation success story. Some former bison hunters, including prominent figures like William “Buffalo Bill” Cody and future President Theodore Roosevelt, gathered the few surviving animals, promoted captive breeding and eventually reintroduced them to the natural landscape.
With the establishment of additional populations on public and private lands across the Great Plains, the species was saved from immediate extinction. By 1920 it numbered about 12,000.
Bison remained out of sight and out of mind for most Americans over the next half-century, but in the 1960s diverse groups began to consider the species’ place on the landscape. Native Americans wanted bison back on their ancestral lands. Conservationists wanted to restore parts of the Plains ecosystems. And ranchers started to view bison as an alternative to cattle production.
More ranches began raising bison, and Native American tribes started their own herds. Federal, state, tribal and private organizations established new conservation areas focusing in part on bison restoration, a process that continues today in locations such as the Tallgrass Prairie National Preserve in Kansas and the Fort Peck Reservation in Montana.
By the early 2000s, the total North American population had expanded to 500,000, with about 90 percent being raised as livestock – but often in relatively natural conditions – and the rest in public parks and preserves. For scientists, this process has been an opportunity to learn how bison interact with their habitat.
Improving prairie landscapes
Bison feed almost exclusively on grasses, which, because they grow rapidly, tend to out-compete other plants. Bison’s selective grazing behavior produces higher biodiversity because it helps plants that normally are dominated by grasses to coexist.
Because they tend to graze intensively on recently burned zones and leave other areas relatively untouched, bison create a diverse mosaic of habitats. They also like to move, spreading their impacts over large areas. The variety they produce is key to the survival of imperiled species such as the greater prairie chicken (Tympanuchus cupido) that prefer to use different patches for different behaviors, such as mating and nesting.
Bison impacts don’t stop there. They often kill woody vegetation by rubbing their bodies and horns on it. And by digesting vegetation and excreting their waste across large areas, they spread nutrients over the landscape. This can produce higher-quality vegetation that benefits other animals.