Washington, Feb 23 The impact of global warming on food prices and hunger could be significant in the next 20 years as a new study reveals that higher temperatures could reduce yields of wheat, rice and maize — dietary staple for millions of poor people who subsist on less than a $1 a day.

Stanford University researchers say that the resulting crop shortages would likely cause food prices to rise and drive many into poverty.

But even as some people are hurt, others would be helped out of poverty, says Stanford agricultural scientist David Lobell.

"Poverty impacts depend not only on food prices but also on the earnings of the poor," said Lobell, a centre fellow at Stanford's Programme on Food Security and the Environment (FSE).

"Most projections assume that if prices go up, the amount of poverty in the world also will go up, because poor people spend a lot of their money on food," adds Lobell.

"But poor people are pretty diverse. There are those who farm their own land and would actually benefit from higher crop prices, and there are rural wage labourers and people that live in cities who definitely will be hurt."

Lobell and his colleagues recently conducted the first in-depth study showing how different climate change scenarios could affect incomes of farmers and labourers in developing countries, says a Stanford release.

He presented the results last Saturday at the annual meeting of the American Association for the Advancement of Science in San Diego.