the Red Sea trade gateway. Despite international court rulings, the countries consider the border dispute unresolved – and their presidents often rally support by threatening to resume the fight.

Kenya Many indigenous tribes lost rights to traditional lands when the British privatized land holdings. When Joseph Kenyatta, the first postcolonial president, sought land redistribution, he gave the most fertile to his Kikuyu tribe. In a later backlash, many Kikuyu were pushed off their pastures. This created ethnic land grievances that have inspired violence during Kenya's elections since the 1990s, most recently after President Mwai Kabaki, a Kikuyu, was accused of stuffing ballot boxes in 2007.

Rwanda The 1994 genocide may have been catalyzed as much by land scarcity as by ethnic tension. Africa's most densely populated country found itself nearlywithout enough land to make farmers trust that they and their children could support themselves. Though the slaughter of minority Tutsis was also ethnically motivated, land fears played no small part in the violence.

Zimbabwe Land grievances helped fuel the 12-year war that led to independence in 1979. But recent violence stems from land reform efforts. In the name of economic fairness, President Robert Mugabe seized white farms and turned them over to blacks, primarily government officials who knew little about farming. As a result, agricultural production plummeted, food became scarce, and inflation spiked. Mugabe held power in a 2008 election only with violent intimidation of Zimbabweans.

Combustible land disputes that could erupt in conflict

Burundi The past decade brought the return of more than a half-million refugees who'd fled violence