Tens of millions of bison once migrated across the United States in enormous herds; tribal oral histories speak of it taking days for an entire herd to pass by. These herds shaped the landscape and performed many ecosystem functions. By the 1890s, the bison population had plummeted to fewer than 1,000 individuals. Since then, dedicated conservation efforts – establishing protected areas and breeding programs – have led to the recovery of the species. There are now about 400,000 bison, mostly existing in small, privately owned herds.
Yellowstone National Park is home to the last significant migratory bison herd. Yellowstone was established as a national park in 1872 providing scientists with a unique opportunity to study how large grazing herbivores affect the landscape. More than 5,000 bison live in the 3,500 square miles of the park.
A 7-year study by researchers examined how bison change the soil and vegetation along their migratory route. What looked like overgrazing turns out to allow plants to keep growing. The bison graze and move on, increasing the density of microbes and nitrogen in the soil and significantly improving the nutrition for other herbivores.
The research validated what Indigenous peoples have known for many generations: that bison helped shape this continent and having large numbers of them improve ecosystems for other animals as well. Native American tribes would like to restore bison to their lands. Whether some of the park fences might be removed to permit migration beyond official borders is under consideration.
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In Yellowstone, Migratory Bison Reawaken a Landscape
Photo, posted August 17, 2017, courtesy of Jacob W. Frank / NPS via Flickr.
Earth Wise is a production of WAMC Northeast Public Radio
