As a recent YouTube video of two young women climbing the border wall in under 20 seconds demonstrates, the assertion that walls slow crossers by minutes is probably too generous.
Nearly 650 miles of solid border wall have already been built, at a cost of $2.6 billion, plus millions more for upkeep and repairs. Unlike the virtual fence, which was scrutinized for a year before being shut down, a recent Government Accountability Office report found that "CBP [Customs and Border Protection] has not assessed the effect of [physical] fencing on border security."
The damages that border walls cause to the environment, however, are easy to see.
Border walls have severely affected rivers, streams, and wetlands. To build walls in the Otay Mountain Wilderness Area, south of San Diego, DHS dynamited 530,000 cubic yards of rock from mountainsides and dumped the waste into the Tijuana River. In Arizona, border walls have acted as dams across washes and streams in the Organ Pipe Cactus National Monument, leading to severe erosion and flooding.