Yellowstone National Park is as wondrous as it is complex. Established primarily to protect hydrothermal 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 an invaluable natural reserve and reservoir of information.

Bison grazing in the grassy areas around a hot spring with snow covering part of the ground.
Greater Yellowstone Ecosystem

Yellowstone is the heart of one of the largest, nearly intact temperate-zones on Earth.

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.

A trail leads to a boulder on top of a hill with snow-capped mountains

A volcano, geysers and other thermal features, earthquakes, and glaciers shape Yellowstone's landscape.

A young bison calf with rust-red fur.

Learn about the park's abundant and diverse species—67 mammals, 285 birds, 16 fish, 5 amphibians, and 6 reptiles.

A dark blue hot spring with a white crested edge rimmed by orange water.
Life in Extreme Heat

Hydrothermal features are habitats for microscopic organisms called thermophiles: "thermo" for heat, "phile" for lover.

Elk graze across a grassy hillside while a forest grows on the mountain-side beyond.

Spring is a time for plant growth, fueling the return of many migratory species.

Red smoke rises from a fire burning a hill of pine trees

Fire is a natural process and shapes the ecosystem.



There is a lot going on in Yellowstone National Park and the Greater Yellowstone Ecosystem. Different organizations, government agencies, and National Park Service offices provide additional information about various natural resource topics within the park and the surrounding ecosystem.

A uniformed man stands in a pit using twine to measure the pit.
Yellowstone Science

Yellowstone Science shares in-depth, science-based knowledge about the Greater Yellowstone Ecosystem.

Three uniformed park employees testing telemetry gear in a meadow.
Yellowstone Center for Resources

Scientific efforts underway in Yellowstone National Park.

Bison grazing in a patch of grass with hydrothermal steam rising behind them.
Learn About the Park

Yellowstone is as wondrous as it is complex. The park is at the heart of the Greater Yellowstone Ecosystem, where nature and culture abound.

Last updated: April 24, 2023

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Contact Info

Mailing Address:

PO Box 168
Yellowstone National Park, WY 82190-0168



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