TWENTY-FIVE million more children will go hungry by the middle of this century as climate change leads to food shortages and soaring prices for staples such as rice, wheat, maize and soya beans.

If global warming goes unchecked, all regions of the world will be affected, but the most vulnerable — South Asia and sub-Saharan Africa — will be hit hardest by failing crop yields, according to the report, prepared by the International Food Policy Research Institute (IFPRI) for the World Bank and Asian Development Bank.

Without an ambitious injection of funds and new technology, wheat yields could fall by more than 30 per cent in developing countries, setting off a catastrophic rise in prices. Wheat prices, with unmitigated climate change, could rise by 170 per cent — 194 per cent by the middle of this century, the report said. Rice prices are projected to rise by 121 per cent — and almost all of the increase will have to be passed on to the consumer. The children of 2050 will have fewer calories to eat than those in 2000, the report says, and the effect would be to wipe out decades of progress in reducing child malnutrition.

The grim scenario is the first to gauge the effects of climate change on the world's food supply by combining climate and agricultural models.

Spikes in grain prices last year led to rioting and unrest across the developing world, from Haiti to Thailand. Leaders at the G20 summit in Pittsburgh last week committed $2bn to food security, and the United Nations is set to hold a summit on food security in November, its second since last year's riots.

But the UN secretary general, Ban Ki-moon, is pressing the World Bank and other institutions to do more. He said the industrialised world needs to step up investment in seed research and to offer more affordable crop insurance to the small farmers in developing countries. Though prices have stabilised, the world's food system is still in crisis, he said at the weekend.

Even without global warming, rising populations meant the world was headed for food shortages and food price rises.

“The food price crisis of last year really was a wake-up call to a lot of people that we are going to have 50 per cent more people on the surface of the Earth by 2050,” said Gerald Nelson, the lead author of the report. “Meeting those demands for food coming out of population growth is going to be a huge challenge — even without climate change.”

The G20 industrialised nations last week began discussing how to invest some $20bn pledged for food security earlier this year.

Southern Asia, which made great advances in agricultural production during the 20th century, was also singled out in the IFPRI report for being particularly at risk of food shortages. Some countries, such as Canada and Russia, will experience longer growing seasons because of climate change.

The report was prepared for negotiators currently trying to reach a global deal to fight climate change at the latest round of UN talks in Bangkok.

— The Guardian, London