Fire has long been both destructive and essential in the tallgrass prairie, an ecosystem that over thousands of years adapted to drought and fire and came to depend on it. Prairie fires began from lightning and from American Indians using fire to hunt bison and ease travel, while later both American Indians and European settlers also used fire to keep grasses short around homes and open land for hunting and pasture. Fall burning helped plants grow earlier in spring, attracted grazing bison, slowed the spread of trees and shrubs, maintained open grassland, burned old plant litter, released nutrients, and exposed soils that warmed faster and encouraged seed germination and prairie grass growth. Prairie plants survive because much of each plant lies underground, allowing quick regrowth from undamaged roots. Although prairie wildfires could spread rapidly, shift direction without warning, and sometimes trap people and animals, fire remains an important management tool today in both remnant and restored prairies, now applied through smaller controlled burns under cooler, less windy, and less dry conditions that reduce risk to wildlife and humans. Tallgrass prairie, named for grasses that can grow more than six feet tall and sustained by root systems reaching more than fifteen feet underground, supports more than nine hundred recorded plant species, resists drought, controls erosion, filters water, enriches topsoil, and helps prevent non-native plants from taking hold. Once stretching from Saskatchewan to Mexico and from east of the Mississippi River west to the Central Great Plains, it covered one-third of Minnesota before European settlement, but only one percent of the state's original tallgrass prairie remains today.