and is republished here by permission. Last year geographer Sam Chambers published an unusual map of the Sonoran Desert. He wasn’t interested in marking roads, mountains and cities. Instead, the University of Arizona researcher wanted to show the distance a young male can walk in various regions of the desert before the high temperature and physical exertion put him at risk of dying from heat exposure or hyperthermia. On the resulting map, red and purple correspond with cooler, mountainous terrain. Yellow and white, which dominate the image, indicate a remote, hot valley. It’s here where migrants seeking to cross between Mexico and the United States are at greatest risk of dying from the desert’s relentless sun.