Prairie
Temperate grassland ecosystem shaped by fire, grazing, and deep-rooted grasses.
Prairies are ecosystems classified within the temperate grasslands, savannas, and shrublands biome, defined by their temperate climate, moderate rainfall, and a landscape dominated by grasses, herbs, and shrubs rather than trees. The term itself is a French loan word for "meadow," ultimately derived from the Latin *pratum*. In North America, "prairie" refers specifically to the lower and mid-latitude regions of the Interior Plains, spanning Canada, the United States, and Mexico. This area includes the entirety of the Great Plains and extends eastward into wetter, more hilly terrain. From west to east, the environment transitions from the dry shortgrass prairie through mixed-grass prairie to the richer, wetter tallgrass prairie. Geographically, the U.S. prairies cover most or all of North Dakota, South Dakota, Nebraska, Kansas, and Oklahoma, along with large portions of Montana, Wyoming, Colorado, New Mexico, Texas, and states to the east such as Minnesota, Wisconsin, Iowa, Missouri, Illinois, and Indiana. The Palouse of Washington and California’s Central Valley are also prairies, while the Canadian Prairies occupy vast areas of Manitoba, Saskatchewan, and Alberta.
The formation of these prairies began with the uplift of the Rocky Mountains, which created a rain shadow reducing precipitation downwind. The parent material for most prairie soil was deposited by glaciers advancing about 110,000 years ago, which scraped and leveled the terrain, then left behind till as they retreated roughly 10,000 years ago. Wind-deposited loess also contributed. Tallgrass prairie evolved over tens of thousands of years through disturbances like grazing and fire. Native ungulates—bison, elk, and white-tailed deer—roamed these lands before European colonization. For 10,000 to 20,000 years, Indigenous peoples used fire annually as a tool for hunting, transportation, and safety, with human activity being the overwhelming ignition source compared to lightning. Fire removed trees, cleared dead plant matter, and altered soil nutrients, while prairie species, with up to 75% of their biomass underground and roots reaching 20 feet deep, readily regrew. Without such disturbance, trees would encroach and shade out the understory. Prairies are divided into tallgrass (over 30 inches of rain yearly), shortgrass (about 12 inches), and mixed-grass types, with wet, mesic, and dry variations fo
- type
- Ecosystem
- biome
- Temperate grasslands, savannas, and shrublands
- location
- North America (Interior Plains of Canada, United States, Mexico; also Palouse of Washington and Central Valley of California)
- key_subtypes
- Tallgrass prairie, mixed-grass prairie, shortgrass prairie
- dominant_vegetation
- Grasses (40–60 species), herbs, shrubs; over 300 species of flowering plants
- key_animal_species
- Bison, elk, white-tailed deer
- rainfall_range
- 12 inches (shortgrass) to over 30 inches (tallgrass) per year
Lore & Background
The formation of the Canadian Prairies started with the uplift of the Rocky Mountains, which cast a rain shadow that lowered precipitation downwind. The parent material for most prairie soil came from the last glacial advance, beginning about 110,000 years ago, when glaciers scraped the landscape and later deposited till as they retreated around 10,000 years ago. Wind-borne loess also contributed to the soil. Tallgrass prairie developed over tens of thousands of years through the disturbances of grazing and fire. Before European colonization, native ungulates such as bison, elk, and white-tailed deer roamed these grasslands. For 10,000 to 20,000 years, Indigenous peoples used fire annually to assist with hunting, transportation, and safety; human-caused fires were overwhelmingly more common than lightning ignitions. Fire removes trees, clears dead plant matter, and alters soil nutrients via ash. Up to 75% of a prairie plant’s biomass is below ground, allowing it to regrow from deep roots (up to 20 feet) after fire. Without disturbance, trees encroach and shade out the understory. Prairie and widely spaced oak trees coexisted in the oak savanna ecosystem.
Reader's Guide
Prairies are ecosystems within the temperate grasslands, savannas, and shrublands biome, characterized by temperate climates, moderate rainfall, and a dominance of grasses, herbs, and shrubs over trees. In North America, the term refers to the Interior Plains, encompassing the Great Plains and wetter, hillier lands to the east, ranging from the drier shortgrass prairie in the west to the richer tallgrass prairie in the east. The parent material of prairie soils was deposited by glaciers and wind-based loess during the last glacial advance, which ended about 10,000 years ago. Tallgrass prairie evolved over tens of thousands of years with disturbances from grazing and fire. Native ungulates such as bison, elk, and white-tailed deer roamed these grasslands before European colonization. For 10,000–20,000 years, Native people used fire annually as a tool, with human ignition sources being overwhelmingly more common than lightning. Fire removes trees, clears dead plant matter, and alters soil nutrients; up to 75% of prairie plant biomass is below ground, allowing regrowth from deep roots. Without disturbance, trees encroach and shade out the understory. Prairie ecosystems are divided into tallgrass (over 30 inches of rainfall yearly), shortgrass (about 12 inches), and mixed-grass prairies. Dominant grasses include Indian grass, big bluestem, side-oats grama, Canada wildrye, and switchgrass. Bison are crucial, as their grazing, trampling, and wallowing shape the environment and increase plant diversity by eating more grass than flowering plants. The Konza Tallgrass Prairie in Kansas hosts 250 native plant species and provides habitat for 208 birds, 27 mammals, 25 reptiles, and over 3,000 insects.
Did You Know?
- The word 'prairie' is a French loan word meaning 'meadow,' ultimately from the Latin 'pratum.'
- Tallgrass prairie evolved over tens of thousands of years with disturbances from grazing and fire, and evidence shows that human-caused fires were overwhelmingly more common than lightning ignitions.
- Bison dung supports over 1,000 insect species, including specialist dung beetles that cannot subsist on the feces of any other animal.
Frequently Asked Questions
What is a prairie?
A prairie is a temperate grassland ecosystem where grasses, flowering herbs, and scattered shrubs dominate the landscape instead of trees. It falls under the broader biome of temperate grasslands, savannas, and shrublands, and thrives in regions with moderate rainfall and seasonal temperature swings.
Where can you find prairies?
Prairies stretch across the Interior Plains of North America, spanning parts of Canada, the United States, and Mexico. Smaller prairie-like areas also exist in the Palouse region of Washington state and California's Central Valley.
What are the main subtypes of prairie?
Prairies are typically divided into three categories based on grass height and moisture: tallgrass, mixed-grass, and shortgrass. Tallgrass prairies support the greatest species diversity, while shortgrass prairies occupy the drier, western reaches of the range.
Why is fire considered essential to prairie ecosystems?
Fire acts as a natural reset mechanism that prevents woody plants from encroaching and keeps the grassland open. Historically, both grazing animals and Indigenous burning practices maintained this cycle, and without periodic fire, prairies would gradually transition into forest.
What makes prairie soil so notable from a geological standpoint?
Prairie soils are exceptionally deep and rich in organic matter, built over millennia by the dense root systems of grasses that penetrate far below the surface. This combination of depth and fertility has made prairie regions some of the most productive agricultural land on Earth, though that same productivity has also driven widespread conversion from native grassland to cropland.
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