'Climate change may super-size sweet potatoes'

Rising levels of carbon dioxide in the atmosphere may double the size of the hardy sweet potato - which is increasingly becoming a staple food in Asia and Africa, researchers say.

Researcher Hope Jahren from the University of Hawaii at Manao and colleagues grew the sweet potato at four CO2 concentrations: the current level of 390 parts per million, as well as 760, 1140 and 1520 ppm.

The Intergovernmental Panel on Climate Change (IPCC) predicts that atmospheric CO2 levels will be between 500 and 1000 ppm by the year 2100, the 'New Scientist' reported.

For the least extreme scenario at 760 ppm, the team found the sweet potato tubers - the fifth most important food crop in the developing world - grew up to 96 per cent larger.

The team is now testing the nutrient content of these tubers.

"Are these sweet potatoes any more nutritious," asks team member Ben Czeck, "or do you have to eat twice as many to get the nutrients needed?"

The previous studies, crucially, revealed the protein content in wheat, rice, barley and potatoes dropped by 15 per cent when grown under CO2 levels double those of today.

Most studies of the effects of higher atmospheric CO2 on crops have shown rising yields of rice, wheat and soy, the report said.

According to researchers at the International Potato Center, the hardy sweet potato is increasingly becoming a staple food in Africa and Asia, producing "more edible energy per hectare per day than wheat, rice or cassava".

The research findings will be presented in December at the American Geophysical Union meeting in San Francisco.

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