After checking for snakes hidden in the dust, Mike Wilson unloads a dozen containers of water from an old pickup truck, ravaged by the passing years.

After saying a prayer, he places the water in the middle of the desert, in the form of a cross. It's for any thirsty migrant, crossing into the United States from Mexico. "Nobody deserves to die for not having a glass of water" he says. "Not here, not on our land."

Wilson is a member of the Tohono O'odham tribe – translated as "People of the Desert" – an indigenous group that has made their home in the desert valleys of southern Arizona and in the north of Sonora during the last thousand years, and in whose reservation, tucked in the heart of the Sasabe desert, have died between 400 and 800 migrants in the recent decade.

Because of its aridity, high population of rattlesnakes, and distance from any housing centers, the reservation has earned the nickname "death row." It is the most dangerous point – and the most well-known – for clandestinely crossing from Mexico into the United States, with perhaps as many as one thousand crossings per day, according to the Border Patrol's calculations.

Although 400 bodies have been found in tribal lands since the year 2000, the humanitarian organization Humane Borders estimates that dozens of migrants' bodies remain lost here, abandoned forever in areas that only members of the Tohono O'odham have permission to enter.

For whites and Hispanics, it's prohibited to cross the borders of this nation, unless they obtain special permission from the tribal government, based in the city of Sells.

"We Tohono O'odham have a moral responsibility when it comes to the migrants," Wilson points out, one of the few humanitarian activists of the indigenous nation. "We cannot allow so many people to continue dying in the desert. But the tribal government doesn't want to assume any responsibility. They prefer to ignore all of the death and suffering in the desert."