The 1 ton animal has the potential to help save an entire ecosystem.

Out on the range, the buffalo are roaming once again.

After a nearly 200-year absence, a small herd of bison have been reintroduced to the Nachusa Grasslands in north-central Illinois, two hours outside of Chicago. This marks the first time since the 1830s that the shaggy beasts have set their hooves east of the Mississippi River. The bison were trucked in last October to graze, spread seeds and churn the soil — all essential to restore Illinois’s tallgrass prairies.

“The word that keeps coming up is surreal,” says Jeff Walk, director of science for The Nature Conservancy’s Illinois chapter, which is heading up the Nachusa preservation efforts. Walk rode with the animals during their eight-hour truck ride from Sioux City, Iowa, and stuck around late into the night to see them unloaded from their trailers.

It was a moment The Nature Conservatory staff had been anticipating for a quarter-century.

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Although it’s known as the Prairie State, Illinois alone has lost more than 99 percent of its grasslands — from 22 million acres to just 2,500 acres, according to the Illinois Department of Natural Resources. Starting in 1986, The Nature Conservancy, considered the country’s largest environmental nonprofit, began buying up neighboring farms in an effort to return a portion of the land to its original state. Today, it now owns or has conservation easements for 3,500 acres. Over an estimated 450,000 hours, volunteers and employees have been weeding out invasive species, regenerating the preserved land through controlled burns and sowing and harvesting seeds for wild petunias, hazelnuts and hawthorne berries. But the bison’s return — at a price of $6 million — is the final stage in the landscape’s restoration.

“We can go around and do the small prairie restorations, but a true native prairie ecosystem has to have bison in it,” Brook McDonald, president of the Conservation Foundation, a nonprofit preserving untouched land in northeast Illinois, tells the Tribune. “Bison were such a significant part of the prairie that whole ecosystems depended on them. Without them, those species go too.”

Aside from a roundup every fall when they are vaccinated, the bison run wild on 500 acres of land hemmed in by a wire fence. (This year, the project will expand to another 1,000 acres.) Standing six feet tall at their shoulders and weighing close to 1 ton, the animals chomp down grasses and avoid flowering plants, increasing biodiversity by creating more light and root space. “The other thing is poop,” Kirk Hallowell, a volunteer steward, tells onEarth, the magazine of the Natural Resources Defense Council. The manure fertilizes the soil and attracts insects, which in turn will hopefully bring back the prairie’s native birds, including the upland sandpiper.

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Like the grassland itself, the bison struggle to reemerge from the devastation that came with settling the West. When the first colonists arrived, up to 60 million roamed the continent; by the beginning of the 20th century, however, excessive hunting had decimated the population and only a few hundred remained, the Wildlife Conservation Society says. In tandem, two symbols of the American pastoral are slowly being restored.

“We know that bison will be good for the prairie,” Walk says. “This is a unique opportunity to understand exactly how they influence the natural habitat. It’s a chance to study and learn, and from there, we can share those results with grassland restoration projects around the world.”

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