We're not advocating backing up a van of cheetahs and letting them go near Tucson.

Obviously, gaining public acceptance is going to be a huge issue, especially when you talk about reintroducing predators. There are going to have to be some major attitude shifts. That includes realizing predation is a natural role, and that people are going to have to take precautions.

Humans will continue to change ecosystems, cause extinctions, and affect the very future of evolution -- either by default or design. The default scenario will surely include ever more pests and weed-dominated landscapes and the extinction of most large vertebrates.

Lions eat people. There has to be a pretty serious attitude shift on how you view predators.

We are not saying this is going to be easy. There are huge and substantial risks and obstacles.

There's always the story of the moving van backing up to the back of the hotel in the middle of the night and cleaning out a room. It doesn't happen often, but it has happened.