While politicians debate border walls as a deterrent to illegal immigration, scientists and environmental activists worry that the man-made barriers could have detrimental effects on wildlife.

Deer, javelina and other animals would face man-made obstacles that impede their migration, they argue, and more roads would mean more land cleared of the plants, rocks and other resources on which Sonoran Desert wildlife rely.

Dan Millis, program coordinator for the Sierra Club's Borderlands Campaign, says his organization is working to raise awareness of this issue among elected officials and local residents.

He says the effort started in Tucson but has spread to other areas along the southern border with Mexico and the northern border with Canada, thanks to volunteers and other participants.

"Our main concern is that border policy has not been very environmentally friendly and we're trying to make it more so, " Millis says.

Millis says the group is particularly worried about recent federal bill HR 1505, which would waive more than a dozen federal environmental protection laws so that the U.S. Department of Homeland Security would not have to follow them.

He says that, although tackling illegal immigration and drug trafficking is important, adding hundreds of miles of walls and barriers is not the way to go.

"I think I would agree with those people in that we both think that our border policies are broken," Millis says. "But going about it in a way where you just throw everything out the window, throw the baby out with the bathwater, so to speak, is really the wrong way to do it."