As one devastating drought follows another, the future is bleak for millions in east Africa. John Vidal reports from Moyale, Kenya

We met Isaac and Abdi, Alima and Muslima last week in the bone-dry, stony land close to the Ethiopia-Kenya border. They were with five nomad families who have watched all their animals die of star vation this year in a deep drought, and who have now decided their days of herding cattle are over.

After three years of disastrous rains, the families from the Borana tribe, who by custom travel thousands of miles a year in search of water and pasture, have unanimously decided to settle down. Back in April, they packed up their pots, pans and meagre belongings, deserted their mud and thatch homes at Bute and set off on their last trek, to Yaeblo, a village of near-destitute charcoal makers that has sprung up on the side of a dirt road near Moyale. Now they live in temporary "benders" – shelters made from branches covered with plastic sheeting. They look like survivors from an earthquake or a flood, but in fact these are some of the world'