A long path to providing a new home for bison to roam

Reintroduction should rebuild other species

MALTA, Mont. — Around 200 chocolate-brown bison raise their heads, following the low growl of a pickup truck slowly motoring across the sagebrush-studded prairie.

Snorting and quietly bellowing, their feral odors riding the wind, they slowly trot across the prairie hills, eager to maintain distance from the truck.

This knot of bison — colloquially referred to as buffalo, though they are not the same species — is part of a project to rebuild a vast shortgrass prairie not only to return large numbers of bison here, but also to eventually restore the complex and productive grassland ecosystem the animals once engineered with their churning hooves, waste, grazing, and even carcasses.

“When you have large numbers on the landscape, they impact everything,” Scott Heidebrink, director of bison restoration for American Prairie, a nonprofit conservation group, said “There are ways that bison were impacting the landscape that we haven’t even thought about.”

Since 2001, American Prairie has been working to create a fully functioning prairie, complete with herds of bison thundering across the landscape and playing their historical ecological role.

Experts originally thought it would take a decade or so to restore the bison-driven grassland ecosystem that would, in turn, replenish native species, including numerous grassland birds, river otters, prairie dogs, grizzly bears and wolves — all of which have been eliminated or diminished, largely by farming and livestock grazing.

However, land costs, politics, and other complications have pushed that goal well into the future. Researchers have since become more realistic, understanding that the original timetable to create such a vast grassland is just not feasible.

Between 30 million and 60 million bison once roamed parts of the United States, primarily in the Great Plains. They were a “keystone” species in a complex ecological web, creating a cascade of environmental conditions that helped other species.

Intact grasslands are productive for biodiversity. In part because of the loss of bison, intact grassland biomes are among the most endangered in the world, and the numbers of many species that depend on them have collapsed.

Agriculture has also taken a huge toll on the prairies. “It’s being plowed up fast and mismanaged for cattle,” said Curt Freese, a wildlife biologist and a founder of American Prairie.

The primary task here now, researchers and managers say, is to increase the number of bison and acres. In 2008, more than two dozen ecologists and experts produced a paper known as the Vermejo Statement, which estimated that to foster a functioning prairie ecosystem, at least 5,000 bison would need to be able to migrate freely on some 450,000 contiguous acres.

The first 16 bison were brought to American Prairie in 2005, and their numbers have grown to 774. The reserve has set a goal to settle 6,000 bison on 500,000 contiguous acres, Heidebrink said. The hardest part of the task, though, has been building up enough land.

Someday, bison on reservations, American Prairie, and nearby wildlife refuges in the United States and Canada may become one vast herd, roaming about 3 million acres. Native American communities in Montana, including the Fort Belknap Reservation and Blackfeet Nation, have their own herds.

A full-blown prairie ecosystem is decades away, and it won’t be cheap: Freese, who is writing a book about the return of wildlife to the plains, estimates it is likely to cost several hundred million dollars.

Studies have demonstrated some of the important ecological effects that bison have on grasslands. A long-term comparative study of bison and cattle on tallgrass prairie in Kansas showed that over 30 years on the land grazed by bison, the richness of native plant species doubled compared with places where cattle grazed, and the presence of bison made the prairie ecosystem more resilient to drought.

Bison act as “ecosystem engineers,” improving not just their own habitats but those of myriad other species including plants, birds and insects.

CREATORS OF HABITATS

Bison once fostered a cascade of environmental conditions that helped other species.