In the Nuba Mountains and Blue Nile, civilians in the rebel areas mostly have run out of food as Sudanese warplanes prowl the sky, driving villagers out of their homes and fields into the mountainsides and bush for protection.

During a weeklong visit to the rebel-held Nuba Mountains in April, a McClatchy correspondent witnessed children rummaging for food in treetops. Several families said they had nothing more to eat. Residents seemed resigned to widespread starvation during the summer rainy season, when road access to the area will be impassable.

“What can I say? Our life is in God’s hands,” Ibrahim Kuku Naher, 48-year old local chief, said in the mountains of Tess, where thousands had gathered under boulders. “Some will pick (food) from trees, but others will die.”

For now it seems that the only way for relief to reach the needy is a peace deal or cease-fire. The Sudanese government has cut off the rebel-held areas from aid organizations, fearing that humanitarian relief will aid the rebellions.

Ryan Boyette, an American aid worker who refused to be evacuated from the Nuba Mountains when the war broke out, said that with markets in the area now empty, up to 800,000 people were eating leaves, sap, roots and bugs to survive.

“Many of the communities in the local area now have no food at all and the other communities have reduced their food intake to try to make it through the rainy season,” Dr. Tom Catena, an American surgeon who’s running a hospital in the rebel-held Nuba Mountains, wrote in an email late last month.

There appears to be no Plan B if famine strikes. In March, Lyman told a Senate Foreign Relations committee hearing that, “if necessary, we will examine ways to provide indirect support to Sudanese humanitarian actors to reach the most vulnerable.”

Some food aid has been entering the Nuba Mountains covertly for months, but it doesn’t appear to be enough. McClatchy witnessed an unmarked truck that was carrying food entering the area from South Sudan, and civilians described having received rations that they said lasted only a few days.

Roads are now impassable due to the summer rains. U.S. officials say air delivery of food aid would require the permission of Sudan, which is unlikely. Humanitarian officials say that thousands could die.

Even after they reach South Sudan, the refugees are finding little relief from their living nightmare.

The Jamam refugee camp in northeast South Sudan sits atop a baked mud floodplain, with dangerously low amounts of fresh drinking water. Since the seasonal downpours began, that camp has overflowed, spilling toilet waste onto the bare earth where refugees sleep and raising mortality rates in the camps, Doctors Without Borders said last week in a statement.

“These people have fled terrible violence in Sudan and lost family members during their arduous journeys for safety, and now they are sitting exposed in refugee camps on a floodplain and dying from preventable diseases due to horrific living conditions,” said Tara Newell, the group’s emergency coordinator in Jamam, who called on the United Nations to find an urgent solution to the crisis.