'An incredible scar': the harsh toll of Trump's 400-mile wall through national parks

Samuel Gilbert visited four distinct wilderness areas near the new border wall, which is fragmenting protected habitats and threatening endangered species

In the 1980s, when Kevin Dahl first began visiting the Organ Pipe Cactus national monument in southern Arizona, the border was unmarked, save for a simple fence used to keep cattle from a ranch in the US from crossing into Mexico. In those days, park rangers would call in their lunch orders at a diner located just across the border.

Since then, a 30ft steel bollard wall has replaced the old barbed wire fence at Organ Pipe. The towering steel barrier cuts through the Unesco reserve like a rust-colored suture.