Greater Yellowstone Ecosystem

Yellowstone National Park forms the core of the Greater Yellowstone Ecosystem (map). At 34,375 square miles, it is one of the largest nearly intact temperate-zone ecosystems on Earth. Greater Yellowstone’s diversity and natural wealth includes the hydrothermal features, wildlife, vegetation, lakes, and geologic wonders like the Grand Canyon of the Yellowstone River.

Heart of an Ecosystem

Yellowstone National Park was established in 1872 primarily to protect geothermal areas that contain about half the world’s active geysers. At that time, the natural state of the park was largely taken for granted. As development throughout the West increased, the park’s 2.2 million acres of habitat became an important sanctuary for the largest concentration of wildlife in the lower 48 states and the Greater Yellowstone Ecosystem.

The abundance and distribution of these animal species depend on their interactions with each other and on the quality of their habitat, which in turn is the result of thousands of years of volcanic activity, forest fires, changes in climate, and more recent natural and human influences. Most of the park is above 7,500 feet (2,286 m) in elevation and underlain by volcanic bedrock. The terrain is covered with snow for much of the year and supports forests dominated by lodgepole pine and interspersed with alpine meadows. Sagebrush steppe and grasslands on the park’s lower-elevation northern range provide essential winter forage for elk, bison, and bighorn sheep.

Water cascades over a cliff into a canyon

Influence of Geology

Geological characteristics form the foundation of an ecosystem.

Two hikers cross a footbridge across a creak near a wetland


Yellowstone waters provide essential moisture to much of the West. They provide recreational opportunities, habitat, and scenery.

Cow elk on a sagebrush-covered hill with large boulders

Cycles and Processes

Cycles and processes are essential connections within an ecosystem. The ecosystem is constantly changing and evolving.

Fall leaves color a valley bounded by mountains

Scenic Photos

Fall colors, winter scenics

A pika with leafy matter hanging out of mouth

Climate Change

Yellowstone's climate is changing. A continued rise in temperature will fundamentally alter the ecosystem.

Bison walk single-file on a path through snow

Winter Ecology

Though the wildlife and plants of Greater Yellowstone are adapted to its cold, snowy winters, surviving the winter season can be a struggle.

Night view of Milky Way and Castle Geyser

Dark Skies

Learn about dark skies, and the importance of darkness to humans and wildlife.

A smoke plume rises into a blue sky across a wide landscape

Air Quality

Yellowstone National Park is a Class I airshed. The largest source of particulate matter in Greater Yellowstone is smoke from wildland fire.

A bull elk bugles in front of a building


The Greater Yellowstone Ecosystem has many sounds with important ecological functions for reproduction and survival. They form a soundscape.

A wide valley with a distant river and mountains


More than 2 million acres of Yellowstone are recommended for federal designation as wilderness. The land is managed as wilderness.

Last updated: September 19, 2017

Contact the Park

Mailing Address:

P.O. Box 168
Yellowstone National Park, WY 82190-0168


(307) 344-7381

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