"Africa can feed itself. And it can make the transition from hungry importer to self-sufficiency in a single generation."

This is the claim of a new book that argues that the world's poorest continent could break its dependence on foreign aid and become a food exporter by realising its rich agricultural potential.

Researchers led by Harvard University professor Calestous Juma said they were challenging pessimistic views of Africa, a continent often associated with images of famine and campaigns such as Live Aid and Comic Relief.

One in three Africans is chronically hungry, according to the UN, despite $3bn (£1.9bn) spent on food aid for the continent annually and $33bn in food imports. Population growth and climate change are growing threats.

But Juma, author of The New Harvest: Agricultural Innovation in Africa, calls on politicians to put agricultural expansion at the heart of decision-making about everything from transport and communications to education and innovation.

Juma said that Africa was the only continent with arable land readily available to expand agriculture, and that southern Sudan alone could feed all Africans if it was properly developed.

"An African agricultural revolution is within reach, provided the continent can focus on supporting small-scale farmers to help meet national and regional demand for food," Juma said.

His proposal includes the modernisation of farms, with new machinery and storage and processing facilities, and the selective use of genetically modified crops. He calls for new roads, energy sources and irrigation projects.

Some African leaders have been criticised for enriching themselves or their militaries. Juma said they had to recognise that "agriculture and economy for Africa are one and the same".

He told the BBC: "It is the responsibility of an African president to modernise the economy, and that means starting with the modernisation of agriculture."

Juma said that food self-sufficiency would require big shifts in policies that have led to dependence on food aid and imports. His book calls for more direct involvement by political leaders in sectors such as water, energy, transport, communications and education.

Juma said the army might refuse if the agriculture minister asked them to build a road to distribute food. "But if the president asks, they will do it," he said. "The president is the commander in chief."

About 70% of Africans are involved in agriculture, but almost 250 million people, or a quarter of the population, are undernourished. The number has risen by 100 million since 1990.

The researchers found that, while food production has grown globally by 145% over the past 40 years, African food production has fallen by 10% since 1960. Only 4% of the continent's crop land is irrigated. Fertilisers, pesticides and high-quality seeds are prohibitively expensive and in short supply.

Juma said: "African agriculture is at the crossroads. We have come to the end of a century of policies that favoured Africa's export of raw materials and importation of food. Africa is starting to focus on agricultural innovation as its new engine for regional trade and prosperity."

The findings were presented in Tanzania today, where the presidents of Tanzania, Kenya, Uganda, Rwanda and Burundi were holding an informal summit to discuss Africa's food security and climate change.

African political and economic analysts welcomed the research. Dr Greg Mills, author of Why Africa Is Poor, said: "Agriculture is one of the areas of competitive advantage that Africa has, but in the past century we've done very badly.

"Africa can do a whole lot more. I don't think every country is going to be self-sufficient, but many countries can be. It's not just about food self-sufficiency; it's getting the balance right between domestic crops and crops for international consumption."

George Mukkath, director of programmes at the charity Farm Africa, said he was in broad agreement with Juma. "There hasn't been much reform of African agriculture. Only 10% of GDP is invested. The question is whether governments are willing to look at it as a priority."

He added: "Climate change makes the whole thing more crucial. There needs to be more investment in technology for crops. "

Fears have been expressed that "land grabbing" – in which wealthy countries buy or lease land in Africa to farm it for their own populations – could hurt Africa's potential for self-sufficiency. Mukkath added: "That needs to be regulated. There needs to be a code of conduct on how investments are made."