U.S. Secretary of Interior Ryan Zinke rode horseback along the border wall in the Buenos Aires National Wildlife Refuge during his first official visit to the border, on March 17.

He rode alongside Tucson Sector Border Chief Patrol Agent Rodolfo Karisch to discuss border security.

“Clearly border protection is mine and the president’s priority,” Zinke said in front of the towering border wall of rust-red metal posts cutting through hills, rolling into the horizon. “Clearly we’re supportive of a wall. Clearly we’re supportive of multiple technologies. And going through what we saw today was a lot of litter, a lot of traffic, a lot of activity—at least signs of activity—and we want to make sure our border is secure.”

Zinke said border security measures should include not just a wall, but technology and sustainable policy.

“We love immigration,” he said. “Our country’s made of immigrants, so we have to have a policy that’s fair, that’s sustainable over the course of time.”

Zinke said that a border wall is important but so is protecting the environment. The Interior Department is the steward of wildlife and Zinke said he needed to ensure the department's actions don't damage that mission. He's leaving it up to the department's expert to determine how to protect wildlife from the environmental damage of a wall.

“Clearly, you want to make sure that a barrier doesn’t adversely affect wildlife, takes into consideration the floodplains,” he said.

The existing wall has already had adverse environmental effects, fragmenting habitats and wildlife corridors.

And during monsoon season, the wall has become a damn, intensifying flooding. In the summer of 2008, when debris piled up against the fence as water rose two to seven feet high, flooding the border towns of Lukeville, Arizona, and Sonoyta, Sonora, and eventually toppling the multi-million-dollar fence.

Chief Karisch, who was showing Zinke around the border, said the footprint created by the wall is less damaging than the traffic it has deterred.

“A wall is just simply another piece that helps us on the border security side,” he said. “It’s not going to solve every problem. But if you can imagine, years ago, volumes of people streaming across here—you’re not hearing that.”

More than 80 percent of the Border Patrol's Tucson Sector is public land, most of which is managed by the Department of Interior. Zinke said the biggest environmental problem he saw was litter.

“Mostly what I saw out there from environmental damage is the unconstrained illegal traffic and the trash left behind,” he said.

Leaving Buenos Aires, Zinke was headed to the Tohono O’odham Nation—whose leadership been staunchly against a border wall on their tribal lands—to talk border security.

“We need a wall. We also need, as the president said, a nice door,” Zinke said. “It’s important for me to go down and talk to the great citizens of Arizona, talk to the tribes and get a tenor of what the temperament is, where there’s an opposition to fences. Our Native Americans have a strong opposition to fence. I’m going to talk to them about that, and then go back to Washington, D.C., and talk to the president.”