At the edge of the Sandhills, the world’s largest intact grassland, sits the Nebraska National Forest. On a clear and windy fall morning in October 2022, flames raged through its dense thicket after an overturned all-terrain vehicle ignited brush. That kindling grew into a blaze that quickly swallowed a youth camp, jumped a highway, and burned through 14,000 acres of private rangeland.

Since then, Greg Wright has used the Bovee Fire, as it was called, as a warning against the region’s out-of-control red cedar population. As a wildlife biologist at the nearby Bessey Ranger District, it’s his job to make sure the grasslands stay intact. And right now, he says, a manmade cancer threatens its existence.

The U.S. Forest Service planted the Nebraska National Forest amid fears of a national timber shortage in the early 1900s. Of the species introduced, Eastern red cedars thrived. Today, they make up more than 50 percent of the forest’s woody growth and have spread far beyond its bounds. Forty-four million acres of the Great Plains have converted to tree cover due to this encroachment. That’s an area roughly the size of Oklahoma.

Their proliferation has coincided with an increase in the magnitude and frequency of extreme fires throughout the region. A type of juniper, Eastern red cedars burn hotter and easier than most other coniferous trees due to oil-rich leaves and low-lying foliage. Once ignited, their dense thickets make fires even more difficult to contain. Not only are they more fire-prone themselves; they are also quick to inhabit areas disturbed by wildfire.

According to projections by the National Oceanic and Atmospheric Administration, the region encompassing the Sandhills, as well as South Dakota’s Black Hills National Forest and Badlands National Park, is expected to see more growth in large fire weeks than anywhere else in the country.

Trying to get ahead of the danger, regional fire managers like Wright have prioritized thinning existing clusters and stamping out signs of early encroachment on grasslands. And thanks to a newly applied mapping technology, managers may soon be able to accurately chart the terrain, assess where efforts should be concentrated, and most importantly, help landowners fully understand the threat.

For close to a decade, a group of researchers at Colorado State University has been using LIDAR to map the spread of red cedars in Nebraska. LIDAR, which stands for light detection and ranging, works similarly to sonar or radar, only with visible light waves. Aircraft beam lasers onto the land below and collect the data that returns; the university team then uses that data to essentially create 3-D maps of the ground, which are used to tell where trees are concentrated.

“By acting faster, we’re able to act cheaper. It’s analogous to detecting a disease as early as possible to have the best chance of survival.”

-Greg Wright

“With something like LIDAR, we can actually map red cedar cover across the entire region from zero to 100 percent and detect some of those earlier stages of encroachment,” said Steven Filippelli, one of the research associates studying innovations in mapping. By graphing the data according to density and strength of LIDAR points, researchers can identify the quantity and size of trees, even saplings. “By acting faster, we’re able to act cheaper,” said Wright. “It’s analogous to detecting a disease as early as possible to have the best chance of survival.”

The ability to pinpoint early growth would also benefit the dozen or so prescribed-burn associations operating in Nebraska. “It doesn’t take anything to kill a three- or four-inch tree,” said Tell Deatrich, a rancher and member of the Loess Canyons Rangeland Alliance. The 80-member association has collaborated on reclaiming more than 90,000 acres of grassland to date. But these volunteer-based organizations, made up of farmers and ranchers, are often strapped for resources.

So far, Filippelli and his team have created maps for Custer County, but their accuracy and readability are works in progress. For instance, the health of the grasslands depends in part on native deciduous trees, and LIDAR mapping can’t always distinguish between these and red cedars, Filippelli said. As a result, his team is testing other algorithms, a process that could take years. The fast speed at which red cedar grows can also cause challenges. “Due to the high cost of LIDAR, it’s unlikely that [new data] will be collected frequently enough for detecting red cedar expansion in real time,” said Filippelli.

Despite these limitations, Filippelli believes the large-scale applicability of mapping fire-prone species is crucial to the future of wildfire management, and not only for Nebraska. “We hope the method we develop could be used to map evergreen tree cover anywhere in the U.S.,” he said.

More than 97 percent of Nebraska is privately owned, meaning there are thousands of landowners who may or may not even be aware of the threat growing on their property. It also means that fire managers in the region need widespread buy-in from these landowners.

A powerful tool at their disposal has been the Rangeland Analysis Platform (RAP), a public geospatial mapping tool released by the USDA in 2018 to help guide land-use decisions. Using satellite-based data gathered since 1986, the platform allows the public to see how red cedars have rapidly converted open fields to woodland in just a few decades.

But RAP’s moderate-resolution satellite imagery and significant margin of error makes it ineffectual when it comes to real-time mitigation. “If the map shows zero percent tree cover, there could in fact be trees present. Or, if it shows 10 percent cover, there could in fact be no trees,” said Filippelli.

While the visual aid has helped managers and prescribed-burn associations educate landowners about the threat of encroachment, convincing them to mitigate using controlled burning is another issue. Ranchers in the Sandhills, a region north of their jurisdiction, have been more reluctant to adopt these methods out of fear that the blazes will impact their rangeland, leaving it barren of grass. “If you went right in and told them, ‘Hey, you guys got to start burning,’ that’s not a good way to get your point across,” said Wright. “It’s a good way to end a conversation.”

Armed with the specificity that LIDAR maps can provide, managers hope to show how targeted and moderate these burns can be. “This technology will be helpful for landowners to see that we can kill these with really safe f ire, and that it will be extremely effective,” said Deatrich. “The default is to do nothing, but we can’t do that in this case. We have to actively manage.”

Spend a weekend exploring the Bessey Recreation Complex of Nebraska National Forest to see firsthand the progression of red cedar encroachment in the Sandhills from east to west.

About the Author

Morgan O’Hanlon is a freelance reporter based in Austin, Texas. When she’s not in a canoe or on her bike, she writes about endurance sports, the outdoors, and politics.

Cover photo of Eastern red cedar trees growing near a river bank in Central Nebraska, courtesy of USFS Bessey Ranger District.

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