By Mark Doyle
BBC News world affairs correspondent
With attention on food shortages in Niger, aid agencies say a vast "hunger belt" is stretching across Africa.
Images of malnourished children prompted global appeals
People across Africa are affected, from Niger in central Africa to Somalia on the Indian Ocean seaboard.
Latest reports from the Famine Early Warning Systems Network say over 20m people are at risk from food shortages.
The broad cross-section of international aid agencies says that urgent action is required in seven countries across Africa.
The dramatic TV pictures from Niger may have pricked the conscience of some donor countries, but a broader look at the continent shows much wider need.
The Famine Early Warning network, made up of a variety of aid agencies including the aid arm of the US government, USAid, says no fewer than seven African states are facing food emergencies.
These are mostly on the fringes of the Sahara desert and stretch from Niger, through Chad and Sudan, to Ethiopia, Eritrea and Somalia.
One factor unites most of the people at risk across Africa.
They rely overwhelmingly on rain-fed or flood-plain agriculture rather than having access to irrigated fields.
When rains are erratic or fail it is a disaster.
It is also no co-incidence that most of the worst affected countries are on the edge of the Sahara.
The desert is advancing and soils across the region are being eroded.
The only long term answer to this situation, aid workers say, is massive investment including the productive harnessing of rivers like the Niger and the Nile.
This massive investment, they say, will need to be guaranteed over many years.
The picture is mixed within the countries affected.
The largest number of people at risk in a single state, for example, is in Ethiopia, where some 10m people are said to be facing food shortages.
But in some parts of Ethiopia an ambitious government plan to provide a safety net for poor people is beginning to bear fruit.
War and peace
Within Sudan, it is the south of the country that is most at risk.
The end of the war in the south has paradoxically made the situation more difficult, with refugees returning home putting land under pressure.
The seventh country facing a food emergency, according to the Famine Early Warning network, is Zimbabwe, where the situation is more complex than the water shortages and lack of irrigation that characterise the other affected states.
Zimbabwe's staple crops, like maize, once fed the entire country
Aid workers say the recent clearances of urban dwellers have created pressure on rural land as townspeople are forced to settle elsewhere.
The slum clearances came on top of the problems caused by President Robert Mugabe's land reforms.
And these illustrate another side of the complex agricultural problems facing Africa.
Giving mechanised, irrigated farms to subsistence farmers will not necessarily improve food security, because they, too, are dependent on rainfall if the farmers who have taken them over do not have the money to maintain the irrigation systems.