American Bison | The Nature Conservancy

How does TNC work with bison to manage grasslands in the Great Plains?

The Nature Conservancy owns and manages herds of bison at 12 preserves across North America. At TNC we consider bison to be important conservation partners in maintaining the health of native prairies and grasslands. Recognizing that most of our native grasslands in North America evolved under the influence of important forces—climate, fire and grazing—we employ bison as conservation partners to restore and maintain grasslands through the important and much-needed soil disturbance that bison (and many domesticated cattle) provide for these unique landscapes.

What does TNC bring to the table?

TNC has long been in the business of protecting and restoring land. Across the Great Plains and beyond, we protect and continue to steward some of the highest quality grassland habitat left in North America. It’s a little-known fact that native grasslands are some of the most endangered and least protected habitat types on Earth. These grasslands are also dependent on periodic disturbance, like fire and grazing, to remain healthy and productive. We work with conservation partners like the National Park Service and the Intertribal Buffalo Council to transfer bison from areas that can become overcrowded, like Wind Cave National Park, to areas that will allow them more room to roam, like Nachusa Grasslands. Additionally, our bison herd managers use the best science available to carefully consider genetic fitness of bison relative to each program’s conservation objectives. By working with bison as conservation partners in this way, The Nature Conservancy is able to make a significant positive impact on native ecology whether on a protected or restored prairie.

What do fragmented grasslands mean for bison?

Prior to colonization and white settlement in North America, bison roamed freely across the vast Great Plains landscape undeterred by obstacles commonly found today like roads, buildings and cities full of people. Since that time, a lot has changed and the native grasslands that once blanketed much of central North America have dwindled to just a small fraction of their former range. What this means for bison is that they no longer have the physical space needed to sustain herd sizes of the past and therefore are not able to roam freely as wild animals like they once did. At TNC preserves, we manage bison to maintain herd sizes within a range that provides them with adequate food, water and social structure, yet does not permanently damage grassland resources. This careful balancing act is done to ensure both bison and grasslands can thrive as conditions around us change.

How does returning bison to native grasslands affect the ecology of these landscapes?

Bison help maintain grassland ecosystems in many ways. These massive animals would travel around 1,000 miles per year, often grazing in the same areas seasonally. Bison would graze in an area and provide the much-needed disturbance healthy grasslands depend on. Then, after this grazing period, the herd would move on to another area for fresh forage dense with nutrients. The cycles of disturbance and rest are essential for working the soil and allowing new forbs and grasses to make their way to the surface. And while the grasslands of pre-colonial times were the result of hundreds of years of these cycles, we know we’re making a positive impact on what remains thanks to the unique impact of this keystone species.