Over 100 years ago, railroads first choo-chooed into the Flint Hills of Kansas. Now a large-scale track expansion is underway. Will progress spoil the United States’ largest remaining tallgrass prairie?

The Flint Hills straddle eastern Kansas and northeastern Oklahoma. They’re named for the area’s flint resources. Native Americans used the plentiful natural rocks to start fires and make tools. The rocky soil prevented early white settlers from plowing the area, so most raised cattle instead of crops.

The Flint Hills region also boasts the largest tallgrass prairie area in North America. At one time, 150 million acres of tallgrass prairie stretched from Texas to Canada. Tallgrass prairie grasses grow up to 10 feet tall. They have roots that extend up to 15 feet deep.

Today, less than 40% of that ecosystem (interacting organisms and their physical environment) survives. The prairie ecosystem prevents soil erosion. It also supports hundreds of pollinating creatures as well as threatened species like prairie chickens.

Each year, cattle ranchers conduct controlled burns. The fires help restore the prairie grasses for cattle grazing. Fires, grasses, cattle: Flint Hills folks cherish their relationship with the prairie.

On that grassy Kansas prairie, BNSF Railway is building a second main line of track. The expansion will help with transporting goods like chemicals, coal, food and beverages, grain, housing materials, and oil by rail.

However, the project involves adjusting three stream locations, building seven bridges, and extending 36 tunnels, according to the U.S. Army Corps of Engineers. That’s a lot of digging in a place proud of its untouched prairies.

No one paid much attention to BNSF’s multi-year plans—until this year, when construction began on a nearly 42-mile stretch of track running from Ellinor to El Dorado, Kansas. Parts of the railroad run right through the Flint Hills and near the Tallgrass Prairie National Preserve.

Kansan Clayton Jamison was shocked when he saw the size of the excavation. “It looked like a bomb went off,” he says. He and others wonder what will happen to their prairie ecosystem.

“We are also a big supporter of the ongoing efforts to preserve the tall grass prairie of the Flint Hills,” BNSF spokeswoman Amy Casas says. Officials insist the earthmoving is short-term. They say workers will restore the area and plant native grasses. It’s true that the company has made big donations to similar restoration projects.

Jamison doesn’t seem convinced yet. “That is a special place,” he says of the Flint Hills. “It hasn’t changed a lot.” He and others would like to keep their slice of prairie just that way.