The parched monotony of northern Kenya rolls by like a looped video reel: sand, rocks, thorns; sand, rocks, thorns. A lone figure breaks the sequence every now and then, emerging from nowhere into the withering heat of the worst drought in east Africa in at least a decade.

Ngilimo Egelan is one of them, a wispy 70-year-old driving a flock of weak-kneed camels and goats in search of water and pasture, vanishing commodities that are needed to sustain the livestock just as the animals should sustain him.