DADAAB, KENYA — For centuries, Adam Abdi Ibrahim's ancestors herded cattle and goats across an unforgiving landscape in southern Somalia where few others were hardy enough to survive.
This year, Ibrahim became the first in his clan to throw in the towel, abandoning his land and walking for a week to bring his family to this overcrowded refugee camp in Kenya.
He's not fleeing warlords, Islamist insurgents or Somalia's 18-year civil war. He's fleeing the weather.
"I give up," said the father of five as he stood in line recently to register at the camp. After enduring four years of drought and the death of his last 20 animals, Ibrahim, 28, said he has no plans to return.
Asked how he proposed to live, Ibrahim shrugged. "I want to be a refugee."
Africa is already home to one-third of the 42 million people worldwide uprooted by ethnic slaughter, despots and war. But experts say climate change is quietly driving Africa's displacement crisis to new heights. Ibrahim is one of an estimated 10 million people worldwide who have been driven out of their homes by rising seas, failing rain, desertification or other climate-driven factors.
Norman Myers, an Oxford University professor and one of the first scholars to draw attention to the unfolding problem, estimated that by 2050 there will be more than 25 million refugees attributable to climate change, which will replace war and persecution as the leading cause of global displacement.
"The numbers could go off the charts," he said.
Africa would be heaviest hit because so many people's livelihoods are dependent on farming and livestock. Many Africans use less water in a day than the average American uses to flush the toilet, so any further declines that might occur because of climate change could be life-threatening.
"Climate change is going to set back development and food production in sub-Saharan Africa at least a decade and perhaps two or three," he said.
It's a reminder that behind the science, statistics and debate over global warming, climate change is already having a deep impact on Africa's poverty, security and culture. And a serious global discussion about climate refugees has barely begun, in part over concerns about who will pick up the tab, some experts say.
So far, there's no comprehensive strategy for coping with climate refugees, who are not yet legally recognized and receive no direct funding. As a result, those fleeing drought, flood and other weather changes usually end up in slums or refugee camps that were set up and funded for other purposes.
"If we were a corporation, climate change is what you might call a 'growth area,' " said Andy Needham, spokesman for the Office of the U.N. High Commissioner for Refugees in Dadaab.
The crisis is apparent at this refugee camp near the Kenya-Somalia border, which was built for 90,000 people and now houses three times as many.
In some cramped corners of the camp, 20 people live in an area not much bigger than a U.S. living room. With no room to expand, graves are being dug up to make space for new huts and much-needed latrines.
Most here are Somalis who have been fleeing insecurity since the 1991 collapse of the Siad Barre dictatorship.
But United Nations officials estimate that as many as 10% of Dadaab's residents are climate refugees. For newcomers, the percentage may be even higher.
"Lately, the majority we see coming here are because of the drought," said Bile Mohamed Ahmed, a refugee who serves as an elected camp leader.
Rukiya Ali Abdirahman, 35, and her husband lived in a southern Somalia region that was largely untouched by clan warfare. The couple tended a small farm, growing food for themselves and selling the excess.
But three years ago, the rainfall began to decrease. Crops failed. So they abandoned their home and came to Dadaab, where he works on odd construction jobs and she makes mud bricks.
"I would have been happy to stay on the farm and die there," she said. "We could have coped with the insecurity. But we couldn't cope with not having anything to eat. That's when we left."
Even some Kenyan farmers and herders have been driven into the camp by drought, though technically Kenyans are not supposed to register because they are not Somalis and not fleeing violence.
The Kenyan government estimates that about 4,600 of its citizens are living in Dadaab. Officials are forcing them to either renounce their citizenship or leave the camp.
Kenyans in the camp say it's unfair to make them choose, because they are just as needy as those fleeing violence.
"The border has never meant anything to us," said one Kenyan herdsman, whose name was withheld for his protection. He lost 250 animals over the last three years. "There was no place else for me to go," he said.