This story about the U.S.-Mexico border wall appeared in the September 2017 issue of National Geographic magazine. National Geographic republished this article on January 14, 2019.

I have been working in the American Southwest for nearly 40 years. In 2004 I came across something I hadn’t seen before: a blue barrel with a plain blue flag on a pole, with “agua” written on the side and several gallons of water inside. I photographed it because it was so unexpected, and it haunted me.

View Images The humanitarian group Water Station put out this barrel of water—one of 160 containers placed throughout the desert regions of the California-Mexico border, where it can reach 120°F or higher. Volunteers of all political stripes monitor these spots every two weeks from spring to fall, checking for activity and refilling the water.

In 2009—as I became aware of an increase in the building of walls and surveillance towers and other government activities along the 1,954-mile-long U.S. border with Mexico—I began photographing in earnest. That’s also when I discovered that the original barrel was a water station placed by a humanitarian group to help prevent the dehydration and death of migrants crossing the border.

The way I have always worked is by focusing on the landscape. Rarely do my images represent people, yet their passage is always felt. The presence of absence.

View Images I assumed this fence near Los Indios, Texas, wasn’t finished when I photographed it, but two years later nothing had changed. Today it functions more like a sculpture than a barrier.

For this project I’d usually fly to a city and rent a four-by-four so I could explore the more remote regions of the border. Sometimes I’d set off a ground sensor, which brought out U.S. Border Patrol agents. Some were terrific—one even came out to protect me because she was worried that cartel activity was nearby—but others could be hostile.

People who don’t live near the border may not realize that there’s already a lot of wall in place—roughly 700 miles. It’s expensive and laborious. You have to design it, fabricate it, pay eminent domain to landowners, then install it. One mile of wall has cost anywhere from $4 million to $12 million.

View Images In remote areas—like this stretch near Ocotillo, California—vehicle deterrents are made of railroad ties. They’re often called Normandy barriers because they look like some of the blockades used during World War II. Border walls that are meant to keep out pedestrians are designed differently—solid or thinly slatted, standing 12 to 16 feet tall.

But how much good does it do? People can climb over it, tunnel under it, and—when it abruptly ends—walk around it.

Functionally speaking, a border wall attempts to do two things. One is to stem migration—people coming into this country for greater opportunity. But only when we stop hiring will they stop coming.

The other is to keep out drugs—but Americans are the ones creating the demand. Until we address the problem successfully on our end, the cartels will find ways to get through. A wall doesn’t stop the reasons that this is happening.

It has been argued that the idea of national sovereignty—that the nation-state has impermeable borders—has already been broken, by everything from the Internet to global capitalism to viruses. Borders are collapsing on an existential level. To me the building of walls seems more symbolic than anything, a desperate gesture.

These images exist where politics, culture, and nature intersect. Although I don’t have answers to these complex problems, I hope my work generates serious contemplation of the issues at hand.

View Images In the Tijuana Estuary south of San Diego, California, a border wall plunges into the Pacific Ocean. That makes it relatively easy for a boat or a Jet Ski—or even a decent swimmer—to bypass.

View Images Older walls are often crude, made from barbed wire or steel panels. But some built in the past decade have been aesthetically conceived. This one—east of Nogales, Arizona—could be mistaken for a Richard Serra sculpture or Jeanne-Claude and Christo’s “Running Fence.”

Richard Misrach’s book Border Cantos , a collaboration with composer Guillermo Galindo, was published in 2016 by Aperture.