Toll Of Climate Change On World Food Supply Could Be Worse Than Thought

ScienceDaily (Dec. 4, 2007) — Global agriculture, already predicted to be stressed by climate change in coming decades, could go into steep, unanticipated declines in some regions due to complications that scientists have so far inadequately considered, say three new scientific reports. The authors say that progressive changes predicted to stem from 1- to 5-degree C temperature rises in coming decades fail to account for seasonal extremes of heat, drought or rain, multiplier effects of spreading diseases or weeds, and other ecological upsets. All are believed more likely in the future. Coauthored by leading researchers from Europe, North America and Australia, they appear in a recent issue of the Proceedings of the National Academy of Sciences (PNAS).

“Many people assume that we will never have a problem with food production on a global scale. But there is a strong potential for negative surprises,” said Francesco Tubiello, a physicist and agricultural expert at the NASA/Goddard Institute of Space Studies who coauthored all three papers. Goddard is a member of Columbia University’s Earth Institute.

In order to keep pace with population growth, current production of grain–from which humans derive two-thirds of their protein–will probably have to double, to 4 billion tons a years before 2100. Studies in the past 10 years suggest that mounting levels of carbon dioxide in the air–believed to be the basis of human-caused climate change–may initially bolster the photosynthetic rate of many plants, and, along with new farming techniques, possibly add to some crop yields.

Between now and mid-century, higher temperatures in northerly latitudes will probably also expand lands available for farming, and bring longer growing seasons. However, these gains likely will be canceled by agricultural declines in the tropics, where even modest 1- to 2-degree rises are expected to evaporate rainfall and push staple crops over their survival thresholds. Existing research estimates that developing countries may lose 135 million hectares (334 million acres) of prime farm land in the next 50 years. After mid-century, continuing temperature rises–5 degrees C or more by then–are expected to start adversely affecting northern crops as well, tipping the whole world into a danger zone.

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