Yellowstone National Park is as wondrous as it is complex. Established primarily to protect geothermal areas that contain about half the world's active geysers, the park also forms the core of the Greater Yellowstone Ecosystem. At 28,000 square miles, it is one of the largest, nearly intact temperate-zone ecosystems on Earth. It preserves a great variety of terrestrial, aquatic, and microbial life.

Natural processes operate in an ecological context that has been less subject to human alteration than most others throughout the nation—and throughout the world. This makes the park not only an invaluable natural reserve, but a reservoir of information valuable to humanity.

View of a a high-elevation landscape with mountains in the background


Greater Yellowstone Ecosystem
The Greater Yellowstone Ecosystem consists of 12-22 million acres and 18,750-28,000 square miles. It is located in Wyoming, Montana and Idaho and encompasses state lands, two national parks, portions of five national forests, three national wildlife refuges, Bureau of Land management holdings and private and tribal lands.


Climate Change
Yellowstone's climate is changing. Climate is one of the primary drivers of the processes that make an ecosystem look and function the way it does.

Glacial erratics and mountains on a cloudy day


Yellowstone was established as the world's first national park primarily because of its extraordinary geology. Its mountains and canyons may appear to change little during our lifetime, but they are highly dynamic.

A grizzly bear stands in sage brush


Yellowstone's abundant and diverse wildlife are as famous as its geysers.

67 species of Mammals
330 species of Birds
16 species of Fish
4 species of Amphibians
6 species of Reptiles
Two purple blooms with yellow and white centers


The vegetation communities of Yellowstone include combinations of species typical of the Rocky Mountains, the Great Plains, and the region to the west.

Hydrothermal Plant Communities
Rare Plants
Trees and Shrubs
Invasive Plants
Yellowstone Herbarium

Smoke rises from flames in a forest on a mountains


Fire is key in shaping the ecology of the Greater Yellowstone Ecosystem. For the first 100 years, managers extinguished fires to preserve park resources. The 1988 fires marked a change in how the public thought about fire in ecosystems. Today, the National Park Service aims to restore fire's role as a natural process as feasible.

A colorful hot spring pool


Other Life Forms: Life in Extreme Heat
The hydrothermal features of Yellowstone are evidence of Earth's volcanic activity. They are also habitats for microscopic organisms called thermophiles—"thermo" for heat, "phile" for lover.

Two bison researchers wearing packs ski across a flat area


Science & Research
Scientists conduct research ranging from large studies of landscape-level changes affecting the local ecosystem to studies of tiny organisms that have the potential to change lives beyond the park boundaries.


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