Under the dust A young Samburu warrior scoops water for cattle from a hole dug into a dry riverbed Photograph by Dominic Nahr for TIME

Head north from nairobi toward Mount Kenya and almost invariably you’ll hit weather. Fog, rain, hail, even snow, all unusual for the equator but a blessing for Mount Kenya’s farmers, who export coffee, roses, green beans and peas to Europe. Once you pass the mountain and descend onto the dusty Samburu plain, however, the weather evaporates. The first town you reach is Archer’s Post, a collection of dusty shacks around a truck stop. From there, says elder Leadisimo Lehgalee, 69, the Samburu are forced to watch the daily deluge over Mount Kenya while enduring a drought on their land that began in 1997. Inevitably, jealousy and desperation turn to enmity. “We rob them,” says Lehgalee. “And they rob us back. We raid each other’s cattle, and we fight, we kill, and we die. That’s the Samburu life.”

The urge to appropriate what’s on the other side of the fence rules much of the Sahel, the belt of scrub and semidesert that runs across Africa between the Sahara to the north and the plains to the south. The wars in Darfur and Somalia and between northern and southern Sudan all have roots in tribal competition for land and livestock. In northern Kenya, scores die every year in clashes over watering holes and cattle. And if all that weren’t enough, lately the Sahara and the Sahel have attracted a new fearsome breed of outsiders, such as al-Qaeda and South America’s cocaine cartels, who use the lawless wastes as sanctuaries and smuggling routes.

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