Yes, the Poppers suggested then that landowners could voluntarily contract with the U.S. Forest Service, seed their land in grass, reintroduce bison, and eventually sell it the federal government. They did not issue a call for wholesale federal and state action.
They long ago acknowledged that a plethora of players would have to be involved in what they regarded as the inevitable decline of the region, which the government — among the many others — could ease by fostering social and market forces already at work, and that have accelerated since.
Yet the Poppers remain convenient for use as a rhetorical device.
Disclosure: I encountered some blowback to the Poppers' work in the early 1990s as an agriculture writer-editor in Texas; I studied their work and its developing legacy while working on a master's degree in history in 2001-2004; I met Frank Popper, who teaches land use planning at Rutgers and Princeton, at a program in Norman in early 2008; and he and I have been Facebook friends since December 2008 — which means mostly just that it's easy for me to get in contact with him.
So I did. Next week: his response to being called out by Texas Tech, and his critique of some of the study's findings.