Famines affecting a billion people will threaten global food security during the 21st century, according to a leading US scientist.

Nina Fedoroff, the US State Department chief scientist, is convinced that food shortages will be the biggest challenge facing the world as temperatures and population levels rise. Food security in the coming years, she said, is “a huge problem” that has been met with little more than complacency. “We are asleep at the switch,” she said.

Her warning echoes comments by John Beddington, Britain’s chief scientist, last week in which he forecast a “perfect storm” of food, water and energy shortages by 2030.

Dr Fedoroff, who advises Hillary Clinton, said famines that strike a billion people are quite possible in a world where climate change has damaged food production and the human population has risen to nine billion.

Population levels have already exceeded six billion and are expected to rise to nine billion by the middle of the century unless action is taken.

Temperatures, which are rising as a result of climate change, are expected to cause savage reductions in productivity in vast areas of the world’s most fertile lands.

During the 2003 European heatwave, she said, crop yields fell by 20 to 25 per cent in France and this is a pattern likely to be repeated on a much wider scale in the future.

Some years will see worldwide heatwaves which will put a great strain on food supplies and, if they take place two years in a row, they could damage crop yields so drastically that they leave a billion people in danger of starvation.

Even wealthy countries like Britain and the United States, said Dr Fedoroff, will struggle to feed many of their citizens, with the poorest in society likely to suffer the most. “I think that’s what we are facing,” she told The Times on a brief visit to London before heading to a OECD conference in Paris later this week, where she will call on governments to do more to guard against food shortages in the coming decades.

“Everybody knows the summer 2003 heatwave killed 30,000 to 50,000 people but do you know it decreased crop productions by 20 to 25 per cent? That’s huge. That summer was an anomoly but the projections are that’s going to be a typical summer. It could be by the mid century, it could be by the end of the century.”

Crop production has already been affected by an increase in drought frequency in parts of Africa but temperature rises forecast as a result of climate change mean that large areas of Europe, the US and central America, Australia and Asia are likely to be similarly affected in the future.

Like Professor Beddington and Bob Watson, the chief scientist at the Department for Environment Food and Rural Affairs, Dr Fedoroff believes genetic engineering must be expanded if the world is going to be able to feed itself.

Genetic modification, she said, can have strong environmental benefits, such as significant reductions in pesticide use, while improving crop yields. Of crucial important will be the ability of scientists to identify genes which enable plants to survive in hot and dry zones so that they can be used to help the most productive crop strains survive and thrive as global warming intensifies.

She said it was important that both GM technologies and conventional crop development were encouraged now because the process of bringing new strains from the laboratory to the field took years.

While addressing crop yields, Dr Fedoroff will tell her audience in Paris this week, scientists must consider other technologies that could help to reduce water shortages.

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