气候变化威胁世界粮食生产

Higher temperatures and changing rainfall patterns resulting from global climate change will threaten food production in many parts of the world - especially regions in the tropics already struggling with food security, according to a new report.

How climate change affects you depends on more than just how it affects your local weather. It also depends on how much the weather matters to your livelihood, and how well you can cope with the changes.

Identifying food insecurity hotspots

Philip Thornton, with the International Livestock Research Institute, is one of the authors of the new report, a joint effort by a group of international agricultural research centers. Thornton and his colleagues wanted to find what they called “hotspots” of future food insecurity: places with the greatest exposure to climate change, highest sensitivity to its impacts, and the least ability to cope with them.

Other studies have looked at the effect of climate change on growing conditions in certain regions. But Thornton says figuring out how that interacts with other factors affecting food security is a challenge.

"It's very difficult to look directly at things like sensitivity of the food systems to climate change impacts, or even the coping capacity of populations to address the impacts. And so we used proxies."

They used a region's cropland area as a proxy for sensitivity to climate change because changes in the weather would have bigger impacts on areas with more farmland. To examine coping capacity, they looked at national data on the prevalence of children stunted by malnutrition.

They combined this data with climate change models that predict the impacts on temperature and rainfall by 2050 to come up with maps of the most vulnerable areas of the tropics.

'Double whammy'

For example, higher temperatures are expected to shorten growing seasons in the tropics. The report looks at areas expected to lose more than 5 percent of the growing season and finds about 370 million people highly vulnerable to this impact.

That area includes much of South Asia, especially India; Nigeria, Niger, Mali and other parts of West Africa; and parts of Sudan, Ethiopia, Uganda, Zambia and other areas of East and Southern Africa.

These are regions, Thornton notes, where hunger is already a problem. "It's almost like a double-whammy, if you like."

Other criteria give smaller impacts. But the basic outlines are the same.

Kansas State University professor Chuck Rice was a member of the 2007 U.N. Intergovernmental Panel on Climate Change. He notes that some of the countries most sensitive to climate change and least able to cope with it, also have among the highest rates of population growth, which puts yet another strain on their food security.

"I think that really pushes the need for increasing funding, not only for research but for outreach efforts to develop mitigation, but also adaptation strategies."

Experts say those strategies include switching to more drought- and heat-tolerant crops, better water management techniques and insurance for crops and livestock to help farmers cope with the climate changes expected during the coming decades.