"The Land Is Ours"

On one side of the fence line, the farmed grass grows thick and trembles in the wind. On the other side, the ground is nearly bare, chewed down in places to the rocky topsoil. In between are splintered fence poles and scattered strands of electric wire that, until last month, closed off a 20,000-hectare central Kenyan commercial ranch from the communal grazing lands of Masai herdsmen.

To the Masai, most of whom make their living raising cows, sheep and goats, the landscape's stark divide is testimony to their need for grazing lands. With a population of about half...