“This region is like the greater Yellowstone ecosystem of the Chihuahuan Desert, and the last true wilderness left in the state of Texas,” says filmmaker/narrator/wildlife biologist Ben Masters. You may know the Big Bend region. You may know that the stunning landscape free from human “improvement” is itself tantamount to a border wall. Now, think about what Trump’s imaginary wall on the ecosystem’s lifeline, the Rio Grande, would do if built.