Bill Sproul lights his ranch on fire every April. So do most of his neighbors in the Flint Hills of eastern Kansas, home to the largest remnant of tallgrass prairie in the United States. People who live in that ocean of swaying green view fire as a boon rather than a burden.
“Fire is what keeps the prairie a prairie,” says Sproul, 68. “If you take out fire, it changes everything.”
After the terrible wildfire seasons in the western United States over the past several years, there has been a renewed interest in prescribed, low-intensity burning as a way of preserving western forests from catastrophic wildfire. But ranchers in the Flint Hills have long understood that regular fires are essential for protecting what remains of the Great Plains’ grasslands from a stealthy invader: trees.
The practice of suppressing fires in the U.S., encouraged by public agencies and cultural norms for the past two centuries, has allowed trees to flourish at the expense of native grasses, which spells bad news for the world’s most endangered ecosystem.
The thriving prairie in the Flint Hills is an exception—and a lesson. Landowners here have kept trees at bay by burning an area the size of Yellowstone National Park each April. Then they turn out one million steers to graze the tender, nutritious shoots rising from the ashes. After three months, the ranchers move their cattle to feedlots to let the prairie regenerate.
Although it may seem unusual, this cycle of fire-graze-grow mimics the processes that have shaped the world’s grasslands for millennia. Indigenous communities embraced fire, burning the prairie regularly to lure in the grazing animals they hunted. But as European settlers spread west, they disrupted this cycle by promptly dousing any flames that threatened their crops or buildings.
“We’re witnessing the death of a biome,” said Dirac Twidwell, a rangeland ecologist at the University of Nebraska. While woody species like mesquite and eastern redcedar are consuming grasslands fastest in the southern and central Great Plains, trees are beginning to creep onto prairies in the northern states, too. “It’s actually pretty simple: When there’s fire, grass wins. Without fire, trees win.”
And, he said, “changing the vegetation affects the entire ecosystem: its wildlife, its profitability, its productivity, and how we live in connection with the land.”
Why grasslands need to burn
Fire is as essential as sunlight for prairie plants. Frequent burns kill tree saplings before they can mature and disperse seeds. The flames also release nutrients in the soil that nourish new grass and flower shoots, and clear out old leaf litter so sunlight can reach them. The absence of fire has shifted the scales in trees’ favor, allowing millions of them to grow tall and reproduce.
“We’ve seen a global shift in humanity's relationship with fire since the Industrial Revolution,” said Twidwell. “We've dictated that fire no longer has a role on landscapes, and that shows a lack of understanding of the fundamental importance of fire ecologically.”
Over small areas, grasslands can boast more plant diversity per square foot than rain forests. In a way they’re like upside-down forests, with deep, dense roots that cycle nutrients, hold water, store carbon, and create some of the most fertile soils in the world. Above ground, the stems and flowers provide habitat for unique wildlife.
When woody species invade, they suck up precious groundwater, change the soil chemistry, and shade out plants that pollinators, birds, and other wildlife rely on.
Many grassland-dependent species, such as the endangered lesser prairie-chicken, abandon habitat once there are more than a few trees per acre.
We’ve already lost nearly half of the world’s grasslands, mainly because most of these flat, fertile spaces have been converted into cropland. The U.S. is still losing one million acres of grasslands every year as farmers till prairie to cultivate single crops like corn, soybeans, or wheat.
But satellite data now show that trees are as big a threat as tractors. A study published in September 2020 shows that in just 20 years (1999-2018), tree cover increased across 44 million acres of the Great Plains—roughly the size of Kansas.
But Twidwell said that “the amount of contaminated grasslands is actually much bigger.” Trees like eastern red cedar, the main offender on midwestern grasslands, spread their copious seeds to sprout saplings up to two football fields away from each invading tree.
It costs at least $250 per acre to restore grasslands once the trees are already dense. Removing mature trees usually requires big machines or expensive chemicals, which doesn’t include the cost of rehabilitating the prairie that was lost beneath them.
“If you multiply 44 million acres by $250, that’s $11 billion,” said Twidwell. “And that’s just to reclaim prairie we’ve lost in the past two decades, not to mention trying to prevent rapid re-invasion as existing trees continue to reproduce.”
Luckily, it only costs about $7 per acre to burn landscapes where tree cover is still low. Plus, fire is a one-stop shop—it can kill seeds, baby seedlings, and mature trees, while also rejuvenating native prairie plants.
“In places where there’s a culture of landowners embracing fire, we still have intact grasslands,” Twidwell says. “That’s where we have hope.”
Fighting trees with fire
In the mixed-grass prairie carpeting Nebraska’s southwestern corner, landowners are fighting trees with fire. A dozen ranchers started the Loess Canyons Rangeland Alliance (LCRA) in 2002 to try to stem the incoming tide of eastern red cedars (which are actually a kind of juniper) with prescribed fire.
“Cows hate cedar trees. So do grasses,” said Scott Stout, a member of the LCRA who raises cattle with his wife and five children. Their ranch had lost nearly half of the grasses that feed their livestock as redcedars took over, translating to lost income. After burning, Stout says tree cover on the ranch fell from nearly 50 percent to 10 percent as the trees died, their seeds incinerated, and the grass returned.
“Burning has done a world of good. It just amazes me why it took us so long to figure it out,” said Stout.
Nearly two decades after its inception, the LCRA has 80 volunteer members who have worked together to safely burn nearly 85,000 acres in total. They’ve also inspired others: Nebraska now has a dozen prescribed burn associations through which landowners share equipment, time, and knowledge to help each other restore healthy grasslands.
The burning has brought back “a sense of camaraderie” among neighbors, Stout said: Everyone chips in, from grandparents to children.
“It’s a family event. We want to make sure the kids are out there to learn, so that fire is a tool that continues on through the generations,” said Stout. It’s the best way to protect the land from tree invasion—and also from catastrophic wildfire.
Shifting the cultural view on fire
Across the Great Plains, from Texas and Oklahoma to the Dakotas, more than 60 landowner-led burn groups have taken root since the 1990s as landowners realize that fire can solve more problems than it creates. It’s an about-face from the attitudes toward fire that have prevailed since settlers began migrating into the Great Plains during the 19th century, fulfilling America’s manifest destiny to colonize the continent.
Hundreds of thousands of intrepid families moved, spurred by a series of federal homestead acts that promised land for free—usually in 160-acre parcels—in exchange for living on and improving the land for five years. The settlers’ ideal of “improvement” was to mimic farming practices in eastern states, where rainfall was abundant, fire was rare, and forests were dense.
Homesteaders not only doused any natural fires, they also began planting millions of trees as windbreaks. Meanwhile, the government forced Indigenous tribes from the grasslands they’d long maintained with fire. That trifecta allowed trees and shrubs to quickly gain ground.
Before European settlement, a swath of tallgrass prairie in the eastern plains would have burned at least every three years due to lightning strikes or Indigenous people igniting blazes, while the mixed-grass prairies further west might have burned every six to 10 years. The local landowners’ groups are trying to reintroduce that historic fire frequency.
But for landowners to burn successfully and at scales that matter, they need the support of local communities, nonprofits, and government agencies. Pheasants Forever, The Nature Conservancy, state fish and game agencies, and the USDA’s Natural Resources Conservation Service (NRCS) are some of the organizations helping landowners cover the costs associated with prescribed burning.
“More than 90 percent of the Great Plains is privately owned, most of it held by agricultural producers,” said Jimmy Bramblett, deputy chief of programs with NRCS, which recently put forth a biome-scale conservation framework that includes incentives for landowners to burn grasslands. “We all benefit from those producers making good environmental stewardship decisions.”
The nitty-gritty of burning
That’s not to say that preserving grasslands is as simple as heading outside with a match. Liza Grotelueschen, a member of the Loess Canyon Rangeland Alliance, said it takes about three years, minimum, to plan and prep for a successful day-long burn. Her family has burned their grasslands twice in the past 15 years, and helps others with fires each spring.
“We have to get the permits, figure out safe exits and burn lines, and then defer grazing there for a year to make sure there’s enough fuel,” said Grotelueschen, a grandmother and retired educator who has attended U.S. Forest Service fire trainings.
First, landowners use chainsaws or other machines to cut down the big trees around the perimeter of the burn, where they keep fuel loads low to control the fire once it’s set. They pile the cut wood near the center of the burn area to fuel the fire.
When it comes time to start the blaze, about a dozen landowners work together to burn 1,500 to 3,000 acres at a time. The flames flicker for four to six hours, and mop-up lasts a few more. Everyone has a job on the burn crew, from ignition, to recording weather conditions, to driving a water truck.
Grotelueschen prefers mop-up duty. She carries a rake, shovel and some water, walking just outside the perimeter to stamp out embers or spot-fires. “We stay until the smoke is gone, and make sure it’s out cold before we leave.”
Though it may take years of careful preparation, it only takes two weeks to see a marked difference in the prairie once it’s burned.
“After our last burn, we saw elk grazing on the new grass and I heard a bobwhite quail on our property for the first time. It’s just beautiful to go out and see the tall grasses growing again and waving in the wind,” Grotelueschen said.
In the Flint Hills to the south, Sproul’s cows are now gorging on fire-enriched grass. They gain nearly three pounds per day as they munch the native plants that evolved in tandem with herds of bison and pronghorn, as well as frequent fires.
“We have a culture here where people are used to fire, where we encourage each other to burn,” said Sproul. “We understand that fire is what keeps our prairies from becoming forests.”