Decades of drought helped trigger Darfur's violence as rival groups fought over scarce water and arable land.
Now, experts fear the war and its refugee crisis are making the environment even worse, leaving the land increasingly uninhabitable and intensifying tensions with no end to the drought in sight.
Darfur's tragedy could be repeated in much of North Africa and the Middle East, experts fear, because growing populations are straining a very limited water supply. Data show rainfall steadily declining in the region, possibly because of weather changes linked to global warming.
"The consciousness of the world on the issue of climate change has to change fast," said Muawia Shaddad of the Sudan Environment Conservation Society. "Darfur is just an early warning."
Darfur's ethnic African farmers and tribes of mostly Arab nomads had long been competing for the region's meager water and land resources, experts say. But the severe droughts of the 1980s and meager rainfall since then sharpened the conflict between the two populations.
When African tribes took up arms against Sudan's Arab-dominated government in 2003, the Arabs in Darfur were willing allies of the government because they already were competing with the farmers for water.
U.N. Secretary-General Ban Ki-moon wrote in a Washington Post editorial earlier this month that the world must learn from the Darfur conflict, including the effects that global warming have on hopes for peace.
Darfur is usually discussed "in a convenient military and political shorthand — an ethnic conflict pitting Arab militias against black rebels and farmers," Ban wrote. "Look to its roots, though, and you discover a more complex dynamic."
Rainfall halved, fueling tension
"In Darfur, we really saw it coming," Shaddad said, pointing to a chart measuring annual rainfall in El Fasher, capital of North Darfur.
The chart shows average annual rainfall has dropped by nearly half since figures were first collected in 1917.
In 2003, when the large-scale conflict began, 7.48 inches of rain fell on El Fasher. Meanwhile, Darfur's population has increased sixfold over the past four decades, to 6.5 million.
That created a strain on resources beyond the capability of the tribes to manage.
As the desert closed in, Arab nomads drifted farther south, bringing their herds of cattle toward lands that African villagers were farming.
Those herds destroyed fields and worsened soil erosion. With land being made unfit for farming, the Africans rebelled when the central government in Khartoum seemed indifferent to their plight.
On a recent morning in southern Darfur, camels grazed aimlessly on what used to be fertile fields. Village after village in the area lay destroyed and abandoned, with houses plundered and water pumps knocked down along the dirt track road winding across the arid landscape.
Nomads have cut down many of the trees in the war zone. Trees are crucial to farmers, because they help stabilize the soil and provide shade for crops. Without them, it will be even harder for farmers now in refugee camps to return to their villages.
In such a fragile environment, even steps designed to reduce human suffering are causing environmental problems.
With an estimated 200,000 people killed and 2.5 million left homeless by the conflict, international relief organizations set up vast camps to care for and protect those at risk.
Aid groups dug bore holes to provide water. Darfur's land is largely hard rock, so most of the scant rain that does fall during the June-September rainy season washes away, and the underground reserves are the only reliable water source. But the wells are depleting that water.
The problem has become so severe that some refugee camps in neighboring Chad may have to be moved soon. In El Fasher's Abu Shouk camp, seven bore holes have already dried up, according to a report by the British aid group Tearfund obtained by The Associated Press.
Furthermore, refugees are rapidly destroying forests around the camps by cutting trees for firewood. Refugees also use wood to reinforce the mud walls of their homes.
Many in the camps also earn money by producing mud bricks, which requires lots of water along with still more wood to fire the kilns. It takes the equivalent of 35 trees to bake bricks in just one kiln, the Tearfund report said.
In Abu Shouk, whole families — including children who don't go to school — could be seen digging hundreds of small holes in the sweltering heat in search of clay for bricks.
Behind them stood a large, barren sand dune that aid workers and conservationists said was covered by a trees only three years ago.
Once the war is over, families who attempt to return to their villages will require more scarce wood to rebuild their homes. A traditional family compound requires the wood from 30 to 40 trees, Tearfund says. That means 12 million to 16 million trees for the 2.5 million refugees, the report said.
With resources so depleted, U.N. and private aid groups are struggling to devise a "do no harm" policy.
In the Es Sallam camp next to El Fasher, a U.S. aid group, International Lifeline, has introduced a redesigned stove that uses up to 80 percent less wood. Nearly three-quarters of the camp's families now use the stoves, said Wahid Jahangiri, an Iranian who spent weeks in Es Sallam teaching women how to operate them.
"We started this as an environmental project and we're only beginning to realize the whole social and cultural impact it's having," said David Welf, the aid group's director.
In southern Darfur, where the damage is less than in the north, aid groups and U.N. agencies are seeking to reconcile farmers and nomads to protect what has not yet been destroyed.
Near the nomad encampment of Damrat Surmi, Arab chiefs have agreed to revive a "peace committee" to manage resources in common with local leaders of the African tribes.
"There used to be forests here, antelopes, even sometimes elephants," said Abdelnumin Adam, an African leader on the peace committee, pointing at the barren landscape.
Abdallah Durru, an Arab representative on the committee, said the Arabs agreed to pay for damage done to crops by their cattle because they realize they must live in harmony with the African farmers.
"We know that when the war ends, the government will leave us on our own," Durru said. "If we can't share this land with our black neighbors, no one can live."
For its part, Sudan's government says it has plans for a pilot project to spend $10 million to replant trees and build dams.
Conceding that amount is "peanuts," Ismail al-Gizouli of the government's High Council for Environment and Natural Resources, said, "We need the richer countries to realize desertification is the emergency and help us."