By Richard Black
Environment correspondent, BBC News
New strains of crops such as cassava will be needed in the tropics
A big push to develop agriculture in the poorest countries is needed if the world is to feed itself in future decades, a report warns.
With the world's population soaring to nine billion by mid-century, crop yields must rise, say the authors - yet climate change threatens to slash them.
Already the number of chronically hungry people is above one billion.
The report was prepared for a major conference on farming and development that opens next week in France.
The first Global Conference on Agricultural Research for Development (GCARD) will bring scientists, policymakers, aid experts, businessmen and pressure groups together in an attempt to plot a way out of the hunger crisis.
"It's a huge problem," said Sir Gordon Conway from the Centre for Environmental Policy at Imperial College London, the conference's keynote speaker.
"We have more than a billion people hungry at the moment, then on top of that we're going to have to feed a growing human population - we're looking at having to double food production by 2050."
The Green Revolution of the 1950s and 60s brought vast increases in yields of crops such as maize and rice to Asia and in South America.
But Africa remained largely untouched; and even in Asia, yields have plateaued.
Fertiliser use on Asian cereal fields has soared 40-fold in 50 years, but yields have only risen about four-fold.
"In Asia, the Green Revolution created a sense of complacency, that we had solved the problem - and that lasted until the [food price] crisis of 2007," said Uma Lele, the former senior World Bank official who co-ordinated the report.
"What we are looking at now is a much more complex 'perfect storm', because all of the 'easy fruit' has been harvested during the Green Revolution."
There was no single, simple measure, she said, that could bring about the yield increases needed in poorer countries, and make sure that the increases were sustainable.
Ensuring all farmers had access to good information about farming methods would be a good start, she noted, but would require different mechanisms in different countries.
Access to facilities also needed to be improved, said Professor Conway.
"Everywhere you go in Africa you can buy Coca-cola or Pepsi-cola, but you can't buy a packet of seeds so easily," he noted.
Aid organisations working together with business had begun to transform that picture, he said; and when African maize farmers had access to the best techniques, their yields could jump fivefold.
But western donors were still more likely to put money into health or education projects than into agriculture, he added, despite the commitment that G8 leaders made at last year's G8 summit in Italy to spend $20bn on agriculture for development.
Crop development needs the full range of technologies, the report says
Despite the burgeoning wealth in South Asia, millions of people remain in stark poverty.
Ninety-seven percent of the chronic hungry live in South Asia or in Africa.
"These two regions of the world are going to be most affected by climate change," said Dr Lele.
"And that's where the majority if the world's poor live; if we don't invest in research now, that's where the problems will be in 10 years' time because developments don't happen overnight."
Combating hunger in these regions, said Professor Conway, meant using every level of technology available, from conventional cross-breeding through to genetic engineering that could specifically give new traits to crop strains.
The much-discussed Golden Rice - enhanced with Vitamin A - was in pre-commercial trials, following years of wrangling about patent issues, he said, and Chinese scientists had developed about 30 GM varieties that were almost ready for commercial release.