One popular definition of sustainability, based on the U.N.-commissioned Brundtland Report (1987), goes like this: "meeting the needs of the present without compromising the ability of future generations to meet their needs." This oversimplifies the report and ignores its intent—to highlight the connections between natural resources, economic disparity, and social justice. Here's a full quotation: "Sustainable development requires meeting the basic needs of all and extending to all the opportunity to fulfill their aspirations for a better life."

The income gap along the U.S.-Mexico border is among the worst anywhere. Yet how are we addressing it? By building a wall: 700 disjointed miles of a 12-to-15-foot-tall barrier spanning parts of Texas, New Mexico, Arizona, and California. At $1.2 billion, it costs nearly $2 million per mile. A ragtag jumble of concrete, steel, and scraps, the completed segments look more like a detention camp than the entrance to a great nation. A far cry from the Statue of Liberty welcoming "huddled masses yearning to breathe free."

Peter Arkle

Worse, the barrier disrupts human communities. Nogales straddles the border between Arizona and Mexico, and for 125 years the only thing marking the line was a four-cable cattle fence. But now the wall cuts the city in half and isolates families and friends on opposite sides. At a hearing in Brownsville, Texas, that included U.S. congressmen as well as state and local officials, a resident pleaded, "It isn't really a border to most of us who live down here."

And by reshaping long stretches of wilderness, the wall could also have enormous ecological consequences. Parts cut through sensitive wildlife refuges and fracture the habitat and migratory routes of jaguars, pygmy owls, and many reptiles. But the Department of Homeland Security exempted the project from normally required environmental reviews141245in order to speed up the process.

Reportedly, 60 percent of U.S. voters have a tolerant attitude toward immigration, favoring greater opportunity for citizenship. Still, if you prefer tighter borders, the fence doesn't work. Even children and seniors can scale it easily, and those who can't simply funnel through the gaps, rerouting rather than preventing the flow of traffic. Increasing the number of guards won't help; the Berlin Wall was manned by soldiers firing live rounds, yet thousands of people still managed to cross it. If the boundary doesn't function, costs a lot, looks terrible, upsets communities, and damages ecosystems, why are we building it?