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Hottest hit hardest - Africa's maize vulnerable to warming climate

By Martin Leggett - 14 Mar 2011 15:16:0 GMT
Hottest hit hardest - Africa's maize vulnerable to warming climate

Sometimes it's looking at old numbers in a new light which provides a fresh insight. That's the case with research published in the first issue of Nature Climate Change (launched this week) into the heat tolerance of corn, or maize. Maize is an important staple grain in parts of the tropics, such as sub-Saharan Africa. It was long thought to be pretty resilient under heat stress, but Stanford scientists working with the International Maize and Wheat Improvement Center have pored through 20,000 maize field trials, and teased out a very different picture.

Although there have been many studies of the effects of a varying climate on maize, in temperate climes as as the US, relatively little focused-research has been conducted into the hottest parts of the planet - the tropics. That omission has now been filled with some clever cross-referencing by Stanford University scientist David Lobell. He took the small-scale field trial records from sub-Saharan African countries, and combined them with local weather-station data across the region. ''It was like sending two friends on a blind date - we weren't sure how it would go, but they really hit it off,'' Lobell said.

The results showed a distinct drop off in yield for maize above 86 F (30 C), - with a greater yield loss the longer and higher that temperature exposure occurs. A temperature rise of a single degree resulted in yield losses in two-thirds of the current maize-growing region. But if drought coincided with the temperature rise, then losses happened in all regions, with three-quarters losing 20% or more of their crop.

Co-author of the study, Marianne Banziger, was concerned ''The pronounced effect of heat on maize was surprising because we assumed maize to be among the more heat-tolerant crops.. The effect is even larger if drought and heat come together, which is expected to happen more frequently with climate change in Africa, Asia or Central America, and will pose an added challenge to meeting the increasing demand for staple crops on our planet.''

A similar research approach is now being investigated for other developing world countries, such as India, China and Brazil. But whilst the research technique offers a promising new tool for assessing climate effects on food crops, it also goes to show the unbalanced focus of resources. Those areas most susceptible to the stress, caused by climate change, are likely to be those without the means to adopt expensive adaptation schemes. Surely it is there that most research efforts should be targeted, especially in the area of food security.