Eminent domain anyone living on the border
The problem is the land that gets stranded behind the fence.
They will pay the landowner for the land that they need to build the fence and the road, but they won't pay for the land that is stranded behind the fence.
The next to last paragraph in the article identifies it:
Private property which could be a house on a lot or farmland. Natural habitats and preserves like a wildlife management area. Cemeteries. State parks and Birding Centers. Bird watching is big business in south Texas. People come from all over the US and world.