But what is undeniable is that the 654 miles of walls and fences already on the US-Mexico border have made a mess out of the environment there. They’ve cut off, isolated, and reduced populations of some of the rarest and most amazing animals in North America, like the jaguar and ocelot. They’ve led to the creation of miles of roads through pristine wilderness areas. They’ve even exacerbated flooding, becoming dams when rivers have overflowed.

http://www.vox.com/energy-and-environment/2017/4/10/14471304/trump-border-wall-animals

BROWNSVILLE, Texas — The promise of a "big, beautiful wall" along America's southern border was a cornerstone of President Donald Trump's campaign. From the moment he announced it during his candidacy kickoff address in June 2015, the proposal was hit with charges of racism and questions of effectiveness.

But during almost two years of heated debate over the wall, there has been an often overlooked issue — the potentially "catastrophic" environmental toll the wall could have on the hundreds of species that span the frontier, activists say.

http://www.nbcnews.com/science/environment/trump-s-border-wall-catastrophic-environment-endangered-species-activists-n748446