Greater Yellowstone
Coordinating Committee

​​Importance to the Ecosystem

​The GYE is considered to be the largest nearly intact ecosystem in the lower 48 United States, containing every major mammal and bird species that was here before the arrival of Europeans. The ecosystem supports populations of wolves, grizzly bears, and wolverines, all strong indicators of a healthy ecosystem. As a result, the GYE has long attracted an awed public and researchers who value the opportunity to conduct cutting-edge wildlife science in the context of coordinated, cross-boundary wildlife conservation efforts. The GYE supports some the greatest wildlife migrations still occurring on the North American continent, with some spanning 100+ miles across public and private land. The GYE also serves as a stopover for many bird species during their annual migrations.

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Status and Trends in Greater Yellowstone

​The GYE’s 22 million acres provide essential ecosystem services for a wide variety of species. To remain resilient, wildlife need healthy ecosystems and secure, unfragmented, and connected landscapes. The GYE provides essential habitat for sustaining a viable population of grizzly bears, whose numbers have grown from approximately 150 bears in 1975 to 965 in 2022. Wolves were extirpated then reintroduced in 1995 and are now widespread throughout the ecosystem. Yellowstone National Park is the only place in the lower 48 states to have a continuously free-ranging bison population since prehistoric times. Species listed under the Endangered Species Act include the black-footed ferret, grizzly bear, Canada lynx, Yellow-billed cuckoo, wolverine, and western glacier stonefly, and the Monarch butterfly is a candidate species.

Wildlife stressors and threats include climate change, increasing human use of the GYE, invasive species, and wildlife disease. The GYE climate is projected to change dramatically through this century, with cascading effects throughout the ecosystem. For example, by 2050 in Cody, WY, the number of days >90 °F will increase by more than 4 weeks, the number of days <32 °F will decline by 5 weeks, the growing season will increase by 5 weeks, and the annual snowpack will decrease by 42%.
As a result, we may see ecosystem shifts, such as woodlands transitioning to grasslands, with the landscape changing to conditions we have never seen before. From 1970 to 2018, the human population in the GYE doubled and housing density tripled. Both are projected to double again by 2050. Chronic wasting disease, bighorn sheep pneumonia, brucellosis, white nose syndrome, chytrid, M. bovis, and moose and wolf diseases are ongoing issues. Migration routes are increasingly threatened by land fragmentation.

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Animal Trails: Rediscovering Grand Teton Migrations, co-produced by the University of Wyoming's Wyoming Migration Initiative and Grand Teton National Park, is a new wildlife documentary chronicling the large mammal migrations of Grand Teton National Park that released online November 8, 2023, showing how the park is biologically and culturally connected to distant habitats in Idaho and Wyoming. Learn more about the film here:​​​​​​​​​​​​​​​​​​​​​