BANFF - Wild bison that once numbered in the tens of millions in North America before being hunted almost to extinction are once again thriving in a pocket of western Canada.
Appearing from a distance as specks against the backdrop of the Rocky Mountains, these animals are also restoring balance at the top of a fragile ecosystem.
North America's largest land mammal -- growing to 900kg and 1.8m high at the shoulders -- suffered a dramatic decline in late 19th century due to hunting and habitat loss as settlers pushed westward.
They were reintroduced to what is now Banff National Park in 2017.
"The moment the bison set foot on that landscape, it felt to me that I brought them home," says Wes Olson, who accompanied the first 16 bison to be released there.
Transferred by helicopter from a biosphere reserve near Edmonton, Alberta, the population has exploded and new births are expected to push their numbers to 100 by year's end.
A Parks Canada report published this week concluded that the reintroduction was a success, and it suggested that due to their robust growth rate, this bison subpopulation -- one of only five that occupy a mere 0.5 percent of their original range in North America -- may no longer be considered endangered within a decade.
As soon as they arrived, Olson says, the ancient ecosystem was suddenly reactivated and the bison appeared to feel right at home, while other forest creatures quickly and "intrinsically" reestablished a symbiotic relationship.
A "keystone species" of the Great Plains, a broad expanse of flatlands that stretch across 13 Canadian provinces and US states, from Alberta to Texas, wild bison, by way of their grazing, have shaped this environment.
These "landscape engineers" are on the move as they graze rather than focus on the same patch of land, with their role somewhat like that of elephants in Africa, explains Marie-Eve Marchand of the International Buffalo Relations Institute.
And with herds mobile like that, grasslands are able to regenerate and better store carbon and water, according to a study by the University of Alberta. Other studies also found that the presence of bison makes them more resilient to drought.
Between 30 and 60 million bison once roamed North America. At the end of the 19th century, there were only a few hundred left.
Their decline had a devastating impact also on Indigenous tribes that relied on the animals for food, as well as clothing, shelter and religious worship.
Their return to Banff, an ancestral gathering place of local tribes, has helped revive "parts of our language, culture and deep, deep spirituality that the first peoples of this place had with the land," says Marchand.