BILLINGS, Mont. - When a couple of academics from New Jersey suggested 18 years ago that the future of the Great Plains might lie in returning to a less developed past, a roar of protest was heard from Texas to Montana.

The concept of "Buffalo Commons" by Frank and Deborah Popper could stir an argument in the West as quickly as water rights in a drought year. Most Montanans dismissed the Poppers as clueless outsiders.

"When we started writing, people were saying 'This is preposterous,'" Deborah Popper said recently in a telephone interview. "But some of it is happening, piece by piece."

Deborah Popper teaches geography at City University of New York's College of Staten Island. Her husband, Frank, teaches land-use planning at Rutgers University in New Jersey. Together they authored "The Great Plains: From Dust to Dust," in the December 1987 issue of Planning magazine, which made them almost as popular on the Plains as an invasion of Mormon crickets.

Even Westerners aren't as apt to scoff these days as population throughout the Great Plains continues to decline, just as they predicted.

"I think on the whole, it went from a completely crazy, Martian idea to a respectable minority opinion," Frank Popper said.

Looking for an alternative to the boom-bust cycle of agriculture on the Plains, the Poppers suggested that parts of the Great Plains that could not environmentally or economically maintain agriculture revert to more sustainable, more natural uses. Natural grasslands with native species, such as bison, might provide more stability than traditional agriculture, they suggested.

"The Buffalo Commons suggests ecologically and economically restorative possibilities for large stretches of the Plains," the Poppers wrote in a 2004 publication. "We foresaw a Plains with new land uses that fell somewhere between traditional agriculture and pure wilderness. Environmental protection and ecotourism would supplement existing agriculture and resource extraction methods. Buffalo and other native animals and grasses would in some places replace cattle, a nonnative species. The shift from corn-fed cattle to grass-fed buffalo would diminish the overall environmental pressures on Plains agricultural land."

The Poppers expected that the federal government would be the catalyst for the Buffalo Commons. When economic ruin of the Great Depression swept away homesteads established two decades earlier, the government intervened and bought back millions of acres. The Poppers reasoned that if farms went under in the '80s bust cycle, in which many farm families left the land, the government would step in again.

It didn't exactly happen that way. Unlike the '30s, the land wasn't abandoned; big farms just swallowed up smaller ones. Land prices continue to rise, even in eastern Montana, and the government doesn't have a bunch of abandoned farms on its hands.

"We actually thought there would be less agricultural production by now, but that hasn't happened," Frank Popper said. They hadn't foreseen the success of very large farm operations.

While the federal government's role didn't measure up to their expectation, the Poppers say that states and nonprofit organization have made moves, at least indirectly, in the Buffalo Commons direction. Some states have established educational programs, he said. Organizations like the National Bison Association and the Montana Bison Association have formed to help producers and promote the business.

And conservation groups, including the Sierra Club, the Nature Conservancy and the American Prairie Foundation, are buying land and easements or lobbying with government agencies to protect the natural landscape, he said.

Adding lands owned by the nonprofit conservation groups, wilderness and wilderness study areas, and Areas of Critical Environmental Concern - a special designation for some federal lands - about 435,000 acres of eastern Montana prairie country have some level of protection.

It's a drop in the bucket considering the tens of millions of acres that make up eastern Montana, but the conservation efforts are a new player on the landscape.

And the Poppers say that some of what they foresaw has occurred at an even faster pace than they expected, especially the continuing decline in population in rural areas across the Great Plains.

"Absent a major shift in technology, the numbers are looking down," Frank Popper said.

Counties with Indian reservations will continue to grow and their populations could spill over into neighboring counties, Deborah Popper said. She's also seen some evidence in Colorado that people are moving away from the mountains. It's more a sprawl outward than a jump from the mountains to the eastern border. But she said it could happen in Montana, too.

Deborah Popper said that before communities start trying to grow in population, they need to understand and appreciate the limits of the land. In the homestead era, everyone assumed there would be enough water to go around.

"There wasn't," she said.