A prairie is a temperate grassland of North America: open land covered by grasses and wildflowers with few trees, kept open by dry summers, fire and grazing.

Why is the Lamar Valley called America's Serengeti?

Because, like the Serengeti, it is an open grassland where large herds of grazing animals, such as bison and elk, live alongside predators like wolves and bears, and they are easy to see.

When were wolves reintroduced to Yellowstone?

Grey wolves from Canada were released in Yellowstone in 1995 and 1996, about 70 years after the last wolves there were killed.

How many bison live in Yellowstone?

The population varies from year to year, typically between about 4,000 and 6,000 animals in recent decades.

Why have most prairies disappeared?

Their deep, fertile soils made them ideal for farming, so most were ploughed for crops or turned into pasture during the 1800s and 1900s.

Bison, wolves and an open sea of grass in Yellowstone's Lamar Valley

Prairie and grassland

3D landscape · Lamar Valley, Yellowstone, USA

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Grasslands once covered much of the interior of North America, from the tallgrass prairies of the east to the shortgrass plains and sagebrush steppe of the west. Similar grasslands are the steppes of Eurasia, the pampas of South America and the veld of South Africa. In this app you can land in the Lamar Valley in the northeast of Yellowstone National Park and explore it in interactive 3D: a broad glacial valley of bunchgrass, sagebrush and summer wildflowers, a winding river, groves of quaking aspen and cottonwood, and lodgepole pines on the hills.

Herds of American bison graze the valley floor, elk move along the edges, pronghorn race across the flats, a wolf pack patrols at a distance, and bald eagles and ravens wait for scraps. It is one of the few places in the world where a large grassland still has nearly its full set of native grazing animals and predators.

Key facts

Model setting: Lamar Valley, Yellowstone, USAA wide river valley in the northeast of the park, around 2,000 m above sea level
Yellowstone: First national park, 1872Mostly in Wyoming, reaching into Montana and Idaho; a UNESCO World Heritage Site
Bison: About 4,000–6,000 in the parkYellowstone's herd has lived there continuously since prehistoric times
Wolves returned: 1995–1996Grey wolves from Canada were reintroduced after being eliminated from the park by the 1920s
Pronghorn: Up to about 90 km/hThe fastest land animal in the Americas, though not a true antelope
Tallgrass prairie left: Under about 5% of its original areaMost was ploughed for farmland in the 1800s and 1900s
Grass roots: Can reach 2–3 m deepMost of a prairie's living matter is underground
Typical plants: Bunchgrasses, sagebrush, wildflowersWith aspen and cottonwood along streams and pines on the hills

Where temperate grasslands are

Temperate grasslands grow in the interiors of continents, where there is too little rain for forest but enough for a thick cover of grass. They include the Great Plains of North America, the steppes stretching from Ukraine to Mongolia, the pampas of Argentina and Uruguay, and the veld of South Africa. Summers are warm, winters cold, and rain falls mostly in spring and early summer.

Yellowstone sits on a high volcanic plateau in the Rocky Mountains. The Lamar Valley was shaped by glaciers during the last ice age, which left a broad, gentle valley floor with scattered boulders, ponds and gravel terraces. Today it is a mix of sagebrush grassland, river meadows and forested slopes.

Why grass wins

Grasses grow from the base of their leaves rather than the tips, so they can be grazed, burned or trampled and quickly grow back. Most of a grassland's living material lies underground in dense, deep roots that survive drought and fire. Trees, in contrast, struggle with dry summers and are killed by frequent fires, so they are confined to river banks, hills and sheltered slopes.

Fire, grazing and drought have shaped grasslands for millions of years. Lightning fires and, for thousands of years, fires set by Native American peoples kept the prairies open. Grazing by bison removes old growth, fertilises the soil and creates a patchwork of short and tall grass that many other animals depend on.

Rich soils

The deep roots of prairie grasses built some of the most fertile soils on Earth, called mollisols. This is why most prairies were turned into farmland, and why the American Midwest is a major grain-growing region today.

Bison, elk, pronghorn and wolves

American bison are the largest land animals in North America, with bulls weighing up to around 900 kg. Tens of millions once roamed the plains before hunting in the 1800s reduced them to a few hundred. Yellowstone is the only place in the United States where bison have lived continuously since prehistoric times. Bison wallow in dust, graze in large herds and are faster and more dangerous than they look.

Elk (wapiti) gather in large herds in autumn, when bulls bugle and spar. Pronghorn are built for speed and endurance, outrunning everything on the plains. Coyotes, grizzly and black bears, bald and golden eagles, ravens and magpies all share the valley.

The return of the wolves

Grey wolves were hunted and poisoned until they disappeared from Yellowstone by the 1920s. In 1995 and 1996, 31 wolves from Canada were released in the park, many of them in the Lamar Valley. Several packs now live in Yellowstone, and the valley is one of the best places in the world to watch wild wolves.

The wolves changed elk behaviour and numbers, provided carcasses for scavengers such as ravens, eagles and bears, and may have helped willows and aspens recover in some places. How large these knock-on effects are is still debated by scientists, but the return of the wolves is one of the best-studied predator restorations anywhere.

Seasons in the valley

Winters are long and cold, often below −20 °C at night, and bison sweep snow aside with their heads to reach the grass beneath. Spring brings calves, green grass and migrating birds. In summer the valley turns green and gold, dotted with wildflowers like lupine, arrowleaf balsamroot and Indian paintbrush. In autumn the aspens turn yellow, elk bugle and the bison rut is in late summer.

Grasslands under pressure

Temperate grasslands are among the most altered biomes on Earth. Most prairie has been ploughed, fenced or developed, and much of what remains is fragmented. Grasslands store a great deal of carbon in their soils, and when they are ploughed much of that carbon is released.

In Yellowstone, management of bison that leave the park in winter, disease concerns from cattle ranching, and the pressures of climate change on snow, drought and fire are continuing issues.

Surprising facts about Prairie and grassland

Most of a prairie is underground: roots of some prairie plants grow two to three metres deep.
Yellowstone's bison are the only herd in the United States that has lived in the same place continuously since prehistoric times.
Pronghorn can run faster than any predator now living in North America; their speed may be a leftover from the extinct American cheetah-like cats.
Only a small fraction of North America's original tallgrass prairie survives; the rest became farmland.
Grass grows from the base of its leaves, which is why it survives grazing and mowing far better than most plants.
Wolves were absent from Yellowstone for about 70 years before they were brought back in 1995.

Frequently asked questions

What is a prairie?: A prairie is a temperate grassland of North America: open land covered by grasses and wildflowers with few trees, kept open by dry summers, fire and grazing.
Why is the Lamar Valley called America's Serengeti?: Because, like the Serengeti, it is an open grassland where large herds of grazing animals, such as bison and elk, live alongside predators like wolves and bears, and they are easy to see.
When were wolves reintroduced to Yellowstone?: Grey wolves from Canada were released in Yellowstone in 1995 and 1996, about 70 years after the last wolves there were killed.
How many bison live in Yellowstone?: The population varies from year to year, typically between about 4,000 and 6,000 animals in recent decades.
Why have most prairies disappeared?: Their deep, fertile soils made them ideal for farming, so most were ploughed for crops or turned into pasture during the 1800s and 1900s.

Keep exploring

The landscapes in Ember’s Universe are procedural 3D scenes modelled on real places. The landforms, plants and light follow the real thing, but the details are generated, not mapped.

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