Grazing bison increase the density of microbes in the soil, leading to the creation of more of the nitrogen that's essential for plant health and growth.
Jacob Frank/National Park ServiceThere were just 23 bison left in Yellowstone National Park in 1902, but today their population has recovered to roughly 5,000.
The bison population has been restored in Yellowstone National Park — and it’s reawakening the ecosystem.
Researchers have found that a herd of migratory bison leaves more nutrient-rich plants in its wake as the creatures move around the park each year. Scientists analyzed the soil and plant diversity in the herd’s migration corridor and discovered that free-roaming bison are crucial to maintaining a healthy and diverse plant community.
Conservationists have long debated whether allowing bison to roam freely could lead to overgrazing issues. However, this new research confirms traditional Indigenous ecological knowledge about the benefit of bison in North American ecosystems.
How Bison Have Helped Yellowstone’s Ecosystem
In a new study published in Science, researchers analyzed the impacts of free-roaming bison in Yellowstone National Park. Thanks to decades of conservation efforts, the park’s bison population has grown to around 5,000 from a low of just 23 in 1902.
Before they were nearly driven to extinction in the late 1800s, bison roamed North American plains, providing food and clothing to Indigenous groups across the landscape. Their population is believed to have once numbered in the tens of millions.
Chris Geremia/National Park ServiceOne of the researchers’ fixed enclosure sites to measure the biomass of grazed and ungrazed areas of the park.
After their numbers dramatically declined, both Indigenous communities and the landscape experienced the long-lasting consequences of the creatures’ absence. This latest research supports the idea that bison played a crucial role in supporting healthy ecosystems in the areas where they used to roam free.
Specifically, researchers found the animals were crucial in promoting the ecosystem’s nitrogen cycle. The migratory bison in Yellowstone increase the amount of microbes in the soil as they graze along their 50-mile route, helping to promote biodiversity along the migration corridor.
“What we’re witnessing is that as bison move across the landscape, they amplify the nutritional quality and capacity of Yellowstone,” study co-author Bill Hamilton, a biology professor at Washington and Lee University, said in a statement. “Their grazing likely has important consequences for other herbivores and for the food web as a whole, similar to the changes that occurred in the Serengeti when the wildebeest population recovered.”
Should Bison Be Allowed To Roam Free? Researchers Say Yes
Whether or not bison should be allowed to roam free has long been debated by scientists and conservationists. Some believe that the movement of bison herds should be controlled in order to prevent overgrazing and the spread of disease. However, the data from this study revealed that there was more plant diversity along the bison migration corridor.
Researchers concluded that in order for the ecosystem to receive the greatest amount of benefits from bison herds, the creatures need to be allowed to roam freely. Currently, most of the roughly 400,000 bison in North America are privately owned livestock.
Chris Geremia/National Park ServiceThe migratory bison herd in Yellowstone travels about 1,000 miles back and forth along a 50-mile route each year.
“If we value a system, we need to allow [bison] to operate as close to naturally as possible. And this was a great case in point of how that can work,” Hamilton told The New York Times. “This kind of serves as an example of how, if large numbers could get large areas of land, what it might look like for restoring bison elsewhere.”
This latest research also validates what Indigenous groups have long known about the role of bison in the ecosystem. Tony Heinert, a member of the Rosebud Sioux tribe and the chief of the branch of bison management for the Bureau of Indian Affairs, told The New York Times that the presence of bison is beneficial for all living things in the region.
“Buffalo helped shape this continent,” Heinert said. “And the more buffalo that are out there, the ecosystems are improved for all other animals as well.”
After reading about how bison have impacted Yellowstone’s ecosystem, learn about how the creatures were nearly hunted to extinction in the 1800s. Then, look through this gallery of Ansel Adams’ photos of Yellowstone and other sites across the American West.
