Millions of people in southern Africa are at risk of extreme hunger because of a combination of poverty, regular bouts of drought and flooding, and the worst HIV/AIDS rates in the world.

The region has had its share of food crises, which forced many to fall back on food aid during periods of severe drought or flood.

But even in years like 2009 when crop yields are relatively high, almost all countries in the region experience pockets of food shortages. People are especially vulnerable during the hunger gap - the period between harvests when food supplies are particularly low - which usually lasts from October to April each year.

Poverty is the main cause of hunger. It means that when crops fail, farmers have to sell assets like animals and tools to make ends meet and men are forced to migrate in search of work. If harvests continue to fail, these coping mechanisms gradually run out and families have nothing to fall back on in times of hardship. A hunger crisis can develop even when markets are well stocked with food because the people who need it most cannot afford to buy it.

Poverty also makes it harder for farmers to adapt to climate change. Even in relatively wealthy South Africa, many farmers are unable to introduce new drought-resistant crops, improve irrigation and so on, because they don't have the means to raise the cash or take out loans.

AIDS has had a dramatic effect on poverty in the region - families have lost their breadwinners and farming has been severely affected. AIDS orphans have had to take over the farming, affecting crop production and the food security of entire regions. (See AIDS in Africa crisis briefing.)

Zimbabwe was once viewed as the breadbasket of the region, but controversial government land reforms, combined with drought and HIV/AIDS, have crippled the country's agriculture.

In the early 2000s, the government took over thousands of white-owned commercial farms and settled tens of thousands of black farmers on the new land. Critics say the new owners do not have the money, expertise or state support necessary to farm the land, and many were forced to turn to fishing, gold panning and sex work to feed themselves.

Meanwhile, most of the wealthy white farmers who had produced the bulk of Zimbabwe's farm exports left Zimbabwe, taking with them knowledge and capital. (See AlertNet's Zimbabwe crisis briefing.)

For more, see African hunger and Food and hunger briefings.