Study Shows Crucial Role for Iconic Species in Prairie Ecosystems
The iconic North American buffalo, which fell to near-extinction levels in the 1880s, is now flourishing, thanks to concerted conservation efforts.
While bison have long been known as a sustainable food and income source, they are now being shown to be an essential part of a prairie ecosystem.
In fact, reintroducing bison to a Great Plains tallgrass prairie ecosystem in the US nearly doubled plant diversity there, says a new study led by Kansas State University (KSU) researchers. The researchers examined the impact of bison on the abundance of native species in prairie landscapes, basing their findings on thirty years of data collected by the 3,487-hectare Konza Prairie Biological Station (KPBS) in Kansas.
KPBS is jointly owned by The Nature Conservancy and KSU.
Building Back the Buffalo Biome
American bison herds once numbered 60 million animals, but they barely survived the massive hunting and disease threats of the 1800s. Herds dwindled to hundreds or even dozens of animals.
Preservation efforts began in earnest by the early 1900s and have never stopped.
“The American bison today is a conservation success story, which has gone from less than 1,000 animals left in the world to approximately 500,000 in North America today,” says National Bison Association Executive Director Jim Matheson.
Bison remain under threat from anthropogenic stressors. Consequently, they are receiving attention from scientists and other stakeholders who hope to see them thrive. Understanding how humans can help bison regenerate prairie ecosystems and maintain healthy bison populations is crucial to species abundance.
The favorable status of bison today is the result of a unique, ongoing collaboration of conservation, agriculture, and public interest in restoring the species, says Matheson.
In North America, bison can currently be found in all fifty US states and every Canadian province. This area represents the animal’s native range. While many of these bison are on private land, the species remains undomesticated. Ranchers and producers use this to their advantage, seeking to develop a robust and regenerative tool to maintain soil health and sequester carbon in bison grazing lands.
Previous studies indicate that bison grazing encourages plant and species diversity. This includes changing the ground cover or patch structure across tallgrass environments.
Bison also tend to “wallow” or vigorously roll around in the dirt. This intense behavior, which helps the animals shed their old coats, relieve insect bites, and add a fresh layer of protective dirt to their hides, leaves behind large, bowl-sized depressions. These “bison wallows” disturb the soil—permitting new vegetation to grow—and create spaces that collect rainwater; these things greatly benefit the ecosystem, researchers have found.
In contrast, another study highlighted how humans in some areas of the world are removing bison grazers, thus decreasing grass and wildflower richness, evenness, and diversity over time.
Contributions to Ecosystem Health
“In high-productivity grasslands, like tallgrass prairie, we see that bison increase the number of plant species and the makeup of the plant community,” says Zak Ratajczak, assistant professor of biology and lead researcher of the KSU study. Areas with bison have less dominant tall grasses, more short grasses typical of drier grasslands, and a much higher abundance of wildflowers, such as goldenrod.
The presence of bison in these grasslands has cascading effects on other parts of the ecosystem. For example, in places where bison graze, grasshopper, bee and other pollinator populations grow.
“We’re now exploring whether bison affect the abundance of woody plants,” says Ratajczak. “The preliminary results are nuanced and suggest that bison might increase woody plants in some places and decrease them in others,” he adds.
Concerns for Climate Extremes
A major concern is that periods of severe heat or drought could become more frequent and intense in the foreseeable future.
“These events can really test the resilience of species and ecosystems,” says Ratajczak.
Based on their current study, the researchers found that plant communities created by bison were resilient to extreme heat in 2011 and extreme drought in 2022. The researchers suspect that the plant species the bison promoted have traits that help them cope with drought. These include new drought-resistant grasses; small, annual plants that reproduce early in the growing season before drought usually sets in; and some wildflowers with very deep roots. (Deep soil is less likely to be depleted during summer droughts).
“I think it is really important to realize that the droughts we could face will be more intense and last longer, which could really test these communities,” Ratajczak adds.
Researchers found that plant communities took between two to four years to recover after a drought. “What we don’t know is whether the plant community would be resilient if another drought occurred before the plant community had time to recover,” says Ratajczak.
Restoration Efforts Require Broad Support
Conservation groups are working to expand bison herds on public and private land across the North American continent. NGOs, the federal governments of Canada and the US, conservation groups, Indigenous communities, and private citizens are involved in bison restoration. “Bison farmers and ranchers are expanding herds to meet growing consumer demand for its clean, delicious, and supremely nutritious meat,” adds Matheson.
A 2022 study on bison as a potential food source said that the “restoration of bison on tribal lands can, under appropriate vision and planning…[provide] a sustainable protein source to communities with some of the greatest food insecurity in the United States.”
This would restore a significant cultural aspect to Indigenous people, adds Matheson.
Progress in Protecting Prairie Health
Bison are now recognized as a keystone species that impacts the overall health in the prairie ecosystem. The National Bison Association in the US has found that when bison flourish, they attract drought-resistant plants, other native flora and fauna, and birds to newly created habitats.
“The future for bison restoration is very bright,” says Matheson. “Efforts on all bison fronts are expanding and have the public’s support across the board,” he adds.
In 2016, the United States enacted the National Bison Legacy Act, which was supported by the National Bison Association, Intertribal Buffalo Council, and the Wildlife Conservation Society. Hailed as a “historic bill,” the National Bison Legacy Act officially names the North American bison as the US national mammal and honors its cultural, historical, and ecological significance.
Sentiment is now firmly focused on the lessons learned from the near-demise of bison and how to manage this legendary species correctly. Along with the “love and dedication the animal has earned from us,” these factors “will ensure its continued return to its native landscape in North America,” says Matheson.
*Natasha Spencer-Jolliffe is a freelance journalist and editor. Over the past 10 years, Natasha has reported for a host of publications, exploring the wider world and industries from environmental, scientific, business, legal, and sociological perspectives. Natasha has also been interviewed as an insight provider for research institutes and conferences.
Interview with Jim Matheson, Executive Director, National Bison Association
Interview with Zak Ratajczak, assistant professor of biology, Kansas State University, and lead researcher