The human depopulation of West Texas (and most of the rest of the Great Plains) may perhaps be having some impact on the populations of various animals. However, hogs seem to be increasing in population even where human population is booming.

I don't think that there's any question that there is a correlation of the high point of rural human population on the plains, about the 1940's, with the low point in most animal populations in the same areas. But modern game management, enforcement of game laws, and more game-friendly land use like CRP have probably had more to do with increased game populations than the decrease in pressure from human predators.