Decades of drought in the Sahel desert and its vast mineral reserves, have forced nomads to defend their pastures from both farmers and foreign investors. Land disputes have erupted into violent conflicts in parts of the Sahel, stretching from Senegal to Sudan, in recent years. This month, violence has escalated in Niger and Mali, involving nomad Tuareg fighters. As nomads are drawn into violence, analysts say it will become even harder for governments to end nomads' isolation and marginalization. Phuong Tran files from N'Djamena, Chad.

Chad's roaming communities, like this one in Mani Kossam, do not show up in population counts. Governments have a hard time tracking clusters of families who periodically move their herds from one rain-fed pasture to the next.

Officials estimate there are about 450,000 nomads and semi-nomads in Chad, roughly five percent of the population.

They say the people of this group are among the country's poorest and least educated, because they typically live in remote areas with little access to health care or schools.

Yousseuf Abdel Kerim, himself a child of Arab nomads, oversees a renewed government effort to enroll children from nomadic families into one of 60 stationary schools recently set up, around the country, for them.

Kerim says past efforts to educate nomads have failed. Officials tried setting up mobile schools that followed migrants during their seasonal treks, but there were not enough teachers. He says the government then tried to build stationary schools along well-traveled routes, but nomads constantly change their routes, based on where it rains.

Kerim says the new strategy is to ask families to leave half their children behind, during seasonal migrations, so the children can attend school.

More than 10,000 children have enrolled, about two percent of the estimated nomadic population.

Senegalese sociologist Djiby Diakhate says, despite efforts to integrate nomads with the rest of the population, there is still a long way to go.

He says there is a historical conflict between nomads and non-nomads. The sociologist says many people persecute nomads as savage outsiders.

Diakhate says this tension can erupt when there are land disputes.

In western Sudan, years of drought have made it harder for Arab camel-herding nomads and non-Arab farmers to share land.

In 2003, the tension exploded in Darfur into interethnic violence. The United Nations says fighting has displaced more than two million people, left hundreds of thousands dead and spread into neighboring Chad and Central African Republic.

British anthropologist and Saharan expert Jeremy Keenan says a shortage of fertile land is also a problem for Tuareg nomads in Niger and Mali.

In the 1990's, they took up arms against their governments, demanding more autonomy and complaining that foreign companies were taking their land to mine uranium.

Earlier this year, some Niger Tuaregs re-launched attacks, saying their government has failed to honor its promises from a 1995 peace deal, which included sharing more uranium wealth.

Niger government officials say most Tuareg demands from the 1990's have been met.

However, anthropologist Keenan says the Niger government is still overlooking how important land in northeast Niger, home to uranium mines, is to nomads.

"You have got possibly one of the most important pastoral zones in the entire Sahelian belt which traditionally has been an area highly valued by many different nomads, not just Tuaregs," said Kenaan.

Niger Tuareg leaders have vowed continued violence until the government stops dismissing them as "drug smugglers" and "bandits," and starts recognizing their demands as legitimate.

Defense officials in Mali have accused Mali-based Tuareg nomads of kidnapping almost 40 government soldiers this week, a tactic also used by Niger's nomad tribes in their seven-month uprising.

No one has claimed responsibility for the kidnappings.

Far from Tuareg territory disputes is Marseique, a Mauritanian desert village.

In this eastern part of the country, near the Malian border, about 70 percent of the population is made up of non-Arab nomads.

Moulkhere, a mother of four, sits on a stone seat by the fire to prepare her family's evening meal.

She says she used to live in the city, but moved her family back to the desert because she prefers the silence and solitude of desert life.

Here, she can raise her girls like she wants.

Moulhkhere says no one bothers them, out here.