The South Ranch is located north of the Fort Peck Lake in northeast Montana. The C.M. Russell National Wildlife Refuge spans both sides of the lake, a distance of more than 100 miles. The ranch covers more than 230 square miles.

A conservation group said today (Aug. 21) it has bought a 150,000-acre Montana ranch in a major step toward its vision of a national park-caliber prairie wildlife preserve that has stoked fears of change in the heart of cattle country, The Associated Press reported.

Steve Page with Page Whitham Land and Cattle confirmed that the family-owned South Ranch near Glasgow had been sold for an undisclosed sum to the American Prairie Reserve. The Bozeman-based group aims to create a multi-million-acre grasslands wildlife complex around northeast Montana’s C.M. Russell National Wildlife Refuge.

Scientists familiar with the reserve describe it as an unprecedented initiative to restore an often-overlooked ecosystem that supports hundreds of species of birds, mammals, plants and insects. The South Ranch purchase more than doubles the amount of land under the reserve’s control. It includes both private land and public land with long-term leases.

Yet some local ranchers see the group’s plans as an assault on their way of life as families that stuck with the cattle business through generations of blizzard and drought are bought out.

Those critics lump the reserve’s goals with a contentious federal proposal to convert a vast swath of eastern Montana into a new national monument — an idea that continues to reverberate more than two years after U.S. Interior Sec. Ken Salazar repudiated it.

The sprawling South Ranch traces its history to a pair of Civil War veterans and professional bison hunters who moved into ranching after bison were wiped out from the area. But Page said restrictions on public grazing and higher government fees — combined with the prospects of a national monument — made ranching on the land no longer viable.

“We have concluded that traditional ranching operations in south Valley and south Phillips counties are in jeopardy of becoming history in the not so distant future,” Page said. “We are not suggesting this to be the correct decision for others, but consider it to be right for us.”

Page said that little will change immediately on the ranch. The terms of the deal give Page Whitham a 12-year lease to continue running cattle on the property.

Yet the ranch is now on path for dramatic alterations over the long term.

American Prairie envisions a herd of up to 10,000 bison roaming its holdings and adjacent federal and state lands. It already has started pulling fences on other properties it has acquired in the area.

“When the reserve is built out, we hope to have a prairie-based, fully-functioning ecosystem which includes the free flow of wildlife across the landscape,” said Scott Laird, American Prairie’s director of land acquisitions. “That is the end-game, but to get there is a coordinated process. There are other people we have to work with — the Bureau of Land Management, the state of Montana and neighbors.”

To date the group has raised $48 million through contributions and pledges. It plans to spend approximately $500 million to build up its land base over the next 20 to 30 years, a figure that includes maintenance costs, said spokeswoman Alison Fox.

The group had total assets of $33 million at the end of 2010, according to its 2010 tax return, the most recent available.

Major donors have included John and Adrienne Mars, candy industry billionaires who have given at least $5 million. Brother Forrest Mars Jr. gave at least $500,000. The chairman of the reserve’s board of directors, Gib Myers, is a California venture capitalist who donated with his wife, Susan, at least $2.5 million.

Donald Kennedy, president emeritus of Stanford University and chairman of the reserve’s scientific advisory council, said most of North America’s grasslands have been drastically altered by grazing, the introduction of non-native plants and other pressures.

The proposed scale of the American Prairie Reserve offers visitors the chance to see those grasslands as they once were, he said.

“They’re getting up to a level on which an awful lot of Americans can visit and develop an idea of what the environment was really like at a time before human occupancy changed it,” Kennedy said.

But for those who still work the land, that prospect puts the fate of the community in doubt.

“They keep saying they’re saving it. But it already looks beautiful. They’re not saving anything,” said Vicki Olson, a reserve opponent and third generation Phillips County rancher. “If they get their way, they’re going to sell it back to the government and they’re going to take it off the tax rolls. It’s going to kill the community economically.”

Reserve representatives said even if their long-term goal is realized, the amount of land involved comprises only a small corner of Montana.