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When you picture Colorado, you likely imagine majestic, towering mountains. Although the mountains are abundant, a large portion of Colorado’s land is high plains. Expanses of prairie grasslands take up 40 percent of the state.

For millennia, vast herds of plains bison (Bison bison) roamed throughout Colorado. Although bison were most abundantly found inhabiting the plains, they ventured into valleys, forests, and even above timberline at times. Throughout the years, the bison population significantly declined due to overhunting by European Americans. By 1889, only 20 of these undomesticated wild bison remained in Colorado. In 1897, the last of these bison were killed.

Grasslands need bison – now read that backwards

The health of Colorado’s grasslands has significantly declined due to the near extinction of bison. Bison are considered a keystone species, which means that their existence plays a vital role in the functioning and health of the ecosystem as a whole.

Ninety percent of bison’s diet consists of the grasses and sedges found growing in grasslands. As bison graze, they trample and wallow (roll around in dirt and mud), which aerates the soil and aids in the dispersal and planting of native seeds.

Bison grazing creates patterns across the landscape, resulting in areas with different heights of grasses and shrubs, and provides multiple habitat options for different species of grassland birds and native plants. Seed dispersal, variety of grass and shrub heights, and thus suitable habitats have diminished without bison. As a result, we have experienced changes in species biodiversity and abundance. Our state’s grasslands need bison.

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Indigenous significance

Aside from their ecological importance, bison have been especially important to the Western Great Plains Indigenous peoples for thousands of years. Nations such as the Arapaho, Cheyenne, and Nuche (Ute) rely on bison as a source of food and materials for various tools and clothing, and would often offer these goods to establish trade amongst Indigenous groups and nations as well as Euro-American nations. They also view bison as spiritual counterparts that provide a vital connection to their land in various ways.

Reintroduction efforts in Colorado

In 1908, there were only 18 bison in Colorado, located at the Denver Zoo. In 1914, the city received more bison from Yellowstone National Park and moved the herd to a 165-acre enclosure at Genesee Park, located in Jefferson County. By 1938, the herd had outgrown its vicinity, so 20 bison were moved to Daniels Park, located in Douglas County.

Over the years, these two herds have continued to expand and are still being managed by humans today. There are at least four herds of bison being managed across the state, such as a conservation herd of 180 bison at Rocky Mountain Arsenal National Wildlife Refuge in Adams County.

Having bison back on the land has had important ecological benefits, such as the renewal of topsoil impacted by overuse and erosion, land renewal via the carrying of seeds in their fur and important microbes in their scat, and restoration of plant species, just to name a few.

There are also indigenous conservation efforts in progress. In 1980, a herd was reintroduced in La Plata County and is still currently being managed by the Southern Ute Tribe. They help in distributing bison meat for tribal members and events, as well as providing education about the role of bison in their culture.

Although the bison that live in Colorado today are classified as livestock rather than wildlife, their reintroduction has aided in the restoration of both our grassland ecosystems and cultural connections to Indigenous groups. These restorations will only continue as herds continue to flourish and grow here in their native landscape, benefiting current and future generations alike.

Callie Pehl is a naturalist at Walking Mountains whose favorite animal is the bison.