At the edge of an oasis almost engulfed by dunes where the rare caravan still passes is a desert landscape punctured by holes.

The salt pans of Kalala near Bilma in northeastern Niger were once an essential stop for traders with their swaying lines of camels.

Salt digging, carried on from generation to generation, was a thriving business, involving a commodity so precious that it was bought and sold across the Sahara and beyond. Over centuries, hundreds of pits have been dug by hand and then filled with water to leach salt from the local rock.

Today, in this isolated desert region plagued by armed gangs and smugglers, the diggers struggle to survive.

Standing in the black and ochre pits, Ibrahim Tagaji and a colleague were wrestling with a crowbar to harvest the bounty – a method of extraction that essentially remains unchanged over time.

A blisteringly hot day when temperatures reached 45C (113F) in the shade was coming to a close.

Barefoot in brine swimming with crystals, the two men dug out salty chunks and pounded them into grains, which were then scooped out with a gourd.

They poured the salt into moulds made from date palms, forming slabs that were then ready for sale.

It is hard work, rewarded by an income that fluctuates according to whichever buyers happen to pass through town.

“When someone with money comes, you earn a lot,” Tagaji said between shovelfuls. “Otherwise, it’s a lot of work, and the money’s poor.”

The local economy offers few alternatives, and roughly half of Bilma’s population still works in the pits, according to local officials.

“As soon as you drop out of school, you have to work here,” said Omar Kosso, a veteran of the industry.

“Every family has its own salt pan. You are with your wife, your children, you come and work.”