Alex McKiernan and Chloe Diegel have plenty of reasons to keep their more than 800 acres near the Nebraska-Kansas border from turning into shrubland and woods.
The land consists of two increasingly rare kinds of landscape — tallgrass prairie and oak savanna, a kind of grassland dotted with centuries-old bur oaks.
It's a place where the ranching family can graze cattle alongside native wildlife, and that matters to them.
"Our job as humans is to figure out how to live productively with what's surrounding us," McKiernan said while driving across the ranch on a four-wheeler. A place like this is "chock full of wildlife and diversity … plants, animals, fungi, everything."
But in many parts of the Midwest and Great Plains, shrubs and trees are taking over age-old grasslands, with repercussions for the ranchers and the wildlife alike.
This family and their ranch manager have tried for years to fight back with the typical tools: burning the grassland, cutting down trees, using herbicide. It's not doing the trick.
"Look across this landscape," McKiernan said. "It's not like one or two trees. There are thousands of trees in front of us and thousands of little woody shrubs."
In 2024, they decided to set aside the herbicide and try another strategy: hungry goats. They hope to hold onto grassland by controlling the woody plants — which the goats are only too happy to eat.
The approach shows promise, and it's also helped boost profits. The cattle ranch, which was operating on thin margins since the family bought it in 2020, has seen revenue double in the first year of having two kinds of livestock instead of one.
Meanwhile, scientists are voicing similar ideas: They say it's possible some grasslands cannot revert to vast, treeless vistas. And they encourage landowners to tailor their approach to what is achievable given the state of their own land and resources.
"In areas that have transitioned into a shrubland or a woodland," said Jesse Nippert, a grassland ecologist at Kansas State University, "you're probably never going to get it back to this idealized pre-colonial landscape painting."
Nippert is lead author on a recent paper in the journal BioScience that calls for protecting intact grasslands where they still exist — but also rethinking goals wherever the transformation is too far advanced for landowners to handle.
"Let's broaden our perspectives about what a healthy ecosystem might look like," he said.
Why are shrublands and woodlands beating out prairies?
McKiernan and his ranch manager, Matt Pirog, have put long hours into targeting woody plants. Often they "hack and squirt," cutting open the trunks to spray in herbicide.
But many resprout, suggesting to them that the labor and chemicals go to waste. McKiernan pointed to glossy green foliage emerging at the foot of a 6-foot-tall Osage-orange tree.
"New basal sprouts," he said. "That tree has been dead for years and it's coming back."
Nearby, a thicket of dogwood bore big clusters of white blooms, apparently thriving despite not one, but two attempts to kill it with herbicide.
Since the plants keep spreading, McKiernan said, the next step would be to fly a plane or drone overhead and coat the whole area with chemicals, which he won't do.
"It'll kill the legumes, it'll kill the native forbs (wildflowers). It will kill every plant that isn't grass," he said. "Why would we spend that money and create this environmental impact that we don't even know the extent of?"
And based on his experience, the woody plants would simply return a few years later.
To understand why the shrubs and trees are so persistent, it's helpful to back up in time.
Before humans reached North America, prairies were scattered pockets of grassland surrounded by forest.
Then humans arrived, possibly during the last ice age. Eventually Indigenous peoples began opening the landscape with intentional fires for many reasons — including to attract bison herds that ate the extra nutritious grasses that regrew afterward.
This helped grow North American grasslands into vast expanses 12,000 to 8,000 years ago. By the 1800s, grasslands covered one-third of North America.
Then human influence changed dramatically, this time tipping the scales in favor of trees and shrubs.
Forced removal of Native Americans ended traditional Indigenous use of fire across most of the continent's grasslands and replaced it with a European culture that largely favored fire suppression.
Industrialization increased the carbon dioxide in the atmosphere by half, which helps woody plants grow faster and survive in drier places. It also triggered climate change, bringing wetter winters and heavier rains that give woody plants a leg up.
A broad range of other factors contribute, too. These range from past overhunting of elk (which eat woody plants) to widespread tree planting and the challenges of carrying out controlled burns now that so many buildings dot the countryside.
All of this opened the door for trees and shrubs to win back space from grasslands, and the process is well underway.
At Oklahoma State University, scientists devised the nickname "the Green Glacier" to describe the layer of woodiness gradually unfurling across the Plains.
At the University of Nebraska-Lincoln, scientists calculated that the Flint Hills — an iconic tallgrass prairie region in Kansas — now has so many woody plants that it grows 1 billion fewer pounds of grass in a year compared to the 1990s.
Similar stories are playing out across the globe, said Nippert, from Kansas State. On every vegetated continent, trees and shrubs are reclaiming space from grasslands.
"We would all love to return to a grassland that we were told it looked like 200 years ago," he said. "But the baseline conditions have changed."
The problem goes beyond losing North America's prairies
As grasslands transition, in many places the new landscapes aren't very diverse.
Often just a relatively small number of woody plant species manages to muscle out a bigger variety of grasses and wildflowers. These areas then lose the complexity that makes them such great habitat, prairie ecologist Marissa Ahlering said.
" When you simplify your plant community, that simplifies all of the other things that depend on it," said Ahlering, who co-authored the research study and serves as the director of science for The Nature Conservancy in Minnesota, North Dakota and South Dakota. "You reduce your bird community, reduce your insect community."
Different woody species are taking over the prairies in different regions. Dense stands of eastern red cedars have become a common sight from Oklahoma to South Dakota — with barely anything growing beneath them.
Kansas and Nebraska ranchers face dogwood and sumac. Their peers in Texas struggle with honey mesquite. In North Dakota, it's aspens and snowberry.
"The problem is, if you get really dense snowberry," Ahlering said, "the only thing that grows underneath it is, like, Kentucky bluegrass."
There's less forage for cattle, too, and it's hard for them to reach with shrubs in the way.
Grasslands typically excel at feeding cattle and bison. It's why the top states for cattle production — Texas, Kansas and Nebraska — are in the middle of the country.
Prairies are also valuable because they support pollinators, protect drinking water from pollution and are home to grassland birds in steep decline. Also, once trees and shrubs move in, tick populations shoot up and wildfires can become more intense.
The scientists who wrote the research paper note that it's possible to develop land management techniques that shape shrubby and woody grasslands into richly diverse places that still support a complex food web and herds of livestock.
Yet doing that will take expanding the conversation beyond a decades-long laser-focus on saving wide-open prairies – a topic that even the study authors admit is difficult to broach.
" I am a prairie lover to my core," Ahlering said. "Having a conversation about 'What does it look like to accept shrubs in a grassland?' kind of feels scary."
A game plan for grasslands that are no longer intact
In areas with lots of trees and shrubs, the authors of the new paper encourage land managers to consider how the ecosystem could still be healthy if reverting to open prairie is not practicable.
"The end goal may start to look different," Ahlering said. "How do we manage this for the diversity that we can (achieve) in this place?"
Where prairie has turned into dense stands of eastern red cedars, for instance, landowners could think about how to nudge it toward open canopy woods, where the trees are diverse and spaced farther apart. This would also create room for more grasses and wildflowers, which would increase livestock forage and habitat complexity.
Having more diversity helps ecosystems stay resilient to climate swings, pathogens and invasive species.
The stakes are also high for protecting water. When woody plants come to dominate grassland on the Great Plains, the streams shrink and the soil gets drier.
" The single biggest threat to our ability to continue to live in Kansas is availability to water," Nippert said. "It's a serious threat to sustainability."
Some parts of the Flint Hills, Sandhills and other regions do still have big stretches of intact grassland, and scientists say those could last long term.
But this will only happen with vigilant land management — particularly controlled fires. That's because the biggest threats to these regions are shrubs that form large colonies via underground runners, including wild plum, sumac and snowberry.
These shrubs can be kept at bay with fire, but if land goes unburned for too long, woody plants get a foothold and shade out grasses. This keeps flames away from them during controlled burns, so that the fires don't kill them.
Historically, burning every three to five years would have been enough to keep out these shrubs. But since they now get a boost from extra carbon dioxide in the atmosphere, burning needs to happen no less than every other year, Kansas State researchers have found. Yet even landowners who are accustomed to carrying out fires could struggle to do that, because burning has gotten harder, more expensive and riskier.
Woody plants as food, not foe
The McKiernan-Diegel ranch is now home to hundreds of goats belonging to two sturdy breeds well-suited to life on the range.
They nibble deftly around the oversized thorns of honey locusts, stripping the leaves without skewering themselves. They denude entire colonies of sumac.
Of course, the plants still resprout.
But with goats on the land, that's now a plus, not a minus. The ranch can sell goat meat year after year.
" We could not pay this mortgage without goats," McKiernan said. And, "if we can learn to match the stocking rate to the woody species, then we can keep the woody species in check."
That could help keep the landscape diverse and grassy enough to graze cattle.
Achieving this will take learning and fine-tuning. They're rotating the goats around the property, observing their impact on the mix of grasses, flowers, bushes and trees.
It's early days, but McKiernan feels far better about this approach.
He never liked using herbicide — case in point, the family's other business is an organic vegetable farm near Lincoln.
So when he and his wife bought the Steinauer ranch, they'd hoped all that "hack and squirt" was a temporary measure to knock back trees and shrubs enough for the grassland system to regain its footing.
Instead, McKiernan found himself trying to kill the same trees and shrubs over and over without beating them. The work was expensive and paid for in large part with public funding.
By switching to goats, he's now free of all this.
"I'm not spending any taxpayer dollars," he said, "and I'm actually generating more revenue for this community and for my family."
Celia Llopis-Jepsen is an environment reporter for Harvest Public Media and host of the environmental podcast Up From Dust. You can follow her on Bluesky or email her at celia (at) kcur (dot) org.
Harvest Public Media is a collaboration of public media newsrooms in the Midwest and Great Plains. It reports on food systems, agriculture and rural issues.
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