The Buffalo Commons is a conceptual proposal to create a vast nature preserve by returning of the drier portion of the Great Plains to native prairie, and by reintroducing the American bison ("buffalo"), that once grazed the shortgrass prairie. The proposal would affect ten states: Montana, Wyoming, Colorado, Oklahoma, New Mexico, Texas, North Dakota, South Dakota, Nebraska, and Kansas.
The proposal originated with Frank J. Popper and Deborah Popper, who argued in a 1987 essay that the current use of the drier parts of the plains is not sustainable. The authors viewed the historic European-American settlement of the Plains States as hampered by lack of understanding of the ecology and an example of the "Tragedy of the Commons". Many people in potentially affected states resisted the concept during the 1990s.
The Poppers note that periodic disasters such as the Dust Bowl and continuing significant population loss over the last 80 years show the area is not sustainable for large-scale farming. They note that the rural Plains has lost a third of its population since 1920. Several hundred thousand square miles of the Great Plains have fewer than 6 persons per square mile. This was the population density standard of settlement which historian Frederick Jackson Turner used in his "Frontier Thesis" to declare the American Frontier "closed" in 1893. Large areas have fewer than 2 persons per square mile. The Poppers demonstrated that the number of "frontier counties" increased by 14 between 1980 and 2000, mostly on the Plains, and noted that there are more than 6,000 ghost towns in the state of Kansas alone (according to Kansas historian Daniel Fitzgerald). They claim that the decline in population on the plains is accelerating.
The Poppers propose that a significant portion of the region be gradually shifted from farming and ranching use. They envision an area of native grassland, of perhaps 10 or 20 million acres (40,000 or 80,000 km2) in size.