As she surveys her small, bare plot in Zimbabwe's capital, farmer Janet Vambe knows something serious is happening, even if she has never heard of climate change.
"Long ago, I could set my calendar with the date the rains started," the 72-year-old said. Nowadays, "we have to gamble with the rains. If you plant early you might lose and if you plant late you might win. We are at a loss of what to do."
Paramu Mafongoya, a University of Zimbabwe agronomist, says Vambe's worries and those of millions of other poor farmers _ most of them women _ across Africa are a clear sign of the impact of climate change on a continent already struggling to feed itself. Changes have been noted in the timing and the distribution of rainfall on the continent. Zimbabweans say the rainy season has become shorter and more unpredictable, Mafongoya said.
Climate change "is a serious threat to human life," Mafongoya said. "It affects agriculture and food security everywhere."
International climate change negotiators meet in the South African coastal city of Durban starting Monday. Their agenda includes how to get African and other developing countries the technology and knowledge to ensure that people like Vambe can keep feeding their families without looking for emergency food aid.
A Green Climate Fund that would give $100 billion a year by 2020 to developing countries to help them fight climate change and its effects was agreed on at last year's climate talks in Cancun, Mexico. Durban negotiators hope to make progress on addressing questions such as where the money will come from and how will it be managed.
Climate change specialist Rashmi Mistry said her anti-hunger group Oxfam will be in Durban lobbying to ensure that women have a voice in managing the Green Fund, and that their needs are addressed when its money is spent. Most small-scale farmers in Africa are women, and they also are the ones shopping for the family's food. But tradition often keeps them out of policymaking roles.
Mistry said when yields are low and market prices are high, women are the first to suffer.
"She's the one usually who will feed her husband first and feed her children first, and she will go hungry," Mistry said.
Across Africa, said Andrew Steer, the World Bank's special envoy on climate change, farmers need to triple production by 2050 to meet growing needs.
"At the same time, you've got climate change lowering average yields by what's expected to be 28 percent," Steer said. He called for more investment in such areas as agricultural research and water management.
Experts already are working on solutions. For example, Africa Harvest, a think tank that uses science and technology to address poverty and improve livelihoods among some of the poorest people in Africa, is working with farmers in an arid stretch in eastern Kenya who were finding it harder and harder to grow their usual crops of corn and beans. Africa Harvest got farmers to switch to sorghum. They have seen bumper harvests as a result because they are focusing on the right crop and the right practices for the climate, said Moctar Toure, chairman of Africa Harvest, who will be in Durban for the talks.
"The way we do agricultural development has to change," Toure told The Associated Press. "We need to balance the need to increase farm productivity with environmental conservation. We will also work towards broad policy changes in our target countries in order to address endemic problems (affecting women) such as land right security, access to credit and knowledge."
Experts worry that one consequence of resources becoming scarcer will be more frequent conflict. Already, Zimbabwe has seen aid used as a political weapon. Those who can prove their loyalty to longtime President Robert Mugabe's party have been seen to be favored when it comes time to hand out seeds or food.
Modern techniques of growing drought-resistant crops like sorghum and millet, staggering planting programs, irrigation and harvesting rain and river water in dams help minimize the risk to farmers. But Zimbabwe's modern agricultural infrastructure has been disrupted by a decade of political and economic turmoil.
Acute food shortages eased after Zimbabwe adopted the U.S. dollar to end world-record inflation in 2009, but local farm production continues to decline. This month, the U.N. food agency said more than 1 million Zimbabweans needed food aid and poor families, especially households with orphans and vulnerable children, can't afford much of the food that is available. Most of that food is imported.
Climate change, like the political problems linked to poverty in Zimbabwe, is manmade, though over a longer term.
Scientists say the accumulation of carbon dioxide traps the Earth's heat, and is causing dramatic changes in weather patterns, agricultural conditions and heightened risks of devastating sea-level rise. Industrialized nations bear the bulk of the blame, since they have been pumping carbon dioxide into the atmosphere for 200 years.
Africa emits only about 3 percent of the total greenhouse gases per year, but its fragile systems and impoverished people are hardest hit by the consequences.
Weather experts say Zimbabwe's average rainfall has decreased over the decade and October temperatures this year soared to above 40 Celsius (104 Fahrenheit), the highest since 1962.
Harare meteorologist Jephias Mugumbate said rains in January and February _ crucial for the ripening of crops _ can no longer be relied on.
It was often said drought in southern Africa recurred every 10 years.
"But now it has become more frequent and intensified. Temperatures show an upward trend and instead of being cooler our nights are becoming hotter," Mugumbate said
Like Vambe, tens of millions of Africans rely on rain-fed agriculture.
Vambe's corn crop has supported her family for more than five decades. But her yields have been steadily falling.
She walks at daybreak to her nearly bare field 10 miles (15 kilometers) from her home in the impoverished western Harare township of Highfield. She has finished planting her seed with the help of her two grandchildren. The dusty brown soil beckons for rain.
Maize, the nation's staple food, needs 60 days of moisture to reach maturity.
"The rains have become erratic. We can no longer rely on the seasons," Vambe said.
She has had to replant on several occasions because of a "false start" to the rainy season.
"This is what has been affecting our yields since 2000. We are no longer getting good yields because the rain comes and goes away," she said.
In the past, the growing season ended in March and harvests were gathered through April.
"Today, nothing is definite. You get rain in April then our maize rots in the fields," Vambe said. "If we are not respecting our spirits and if they are angry, there will be no rain."
Associated Press Writer Donna Bryson in Johannesburg contributed to this report.