Tropics and subtropics will bear the brunt of global warming, warns a new report. But the temperate regions are not going to escape unscathed either, economically or environmentally.
Rapidly warming climate is likely to seriously alter crop yields in the tropics and subtropics by the end of this century and, without adaptation, will leave half the world's population facing serious food shortages, according to a study to be published on Friday in Science Magazine.
The population of this equatorial belt is among the poorest on Earth and is growing faster than anywhere else, the study said.
"The stresses on global food production from temperature alone are going to be huge, and that doesn't take into account water supplies stressed by the higher temperatures," David Battisti, lead author of the study, said.
Battisti, also a professor at the University of Washington, collaborated with Rosamond Naylor, director of Stanford University's Program on Food Security and the Environment, to examine the impact of climate change on the world's food security.
By combining direct observations with data from 23 global climate models drawn by the Intergovernmental Panel on Climate Change (IPCC), co-winner of the 2007 Nobel prize, Battisti and Naylor determined that there is greater than a 90 percent probability that by 2100 the lowest growing-season temperatures in the tropics and subtropics will be higher than any temperatures recorded there to date.
The IPCC estimates that for degree Celsius the average growing season temperatures rise, grain harvests will fall by between 2.5 and 16 percent.
The food crisis of 2008, when growing grain demands and fears of drought caused rice prices to spike by 50% in two weeks in March, made graphically clear the precariously interconnected nature of global agriculture. Some countries cut rice exports, driving prices even higher; others outlawed private hoarding of food; and riots broke out in 33 countries.
A decades-long drought finally ended in the Sahel region of Africa, but was followed by rising temperatures. Farming has been crippled, perhaps permanently. An estimated 275,000 children die there each year from malnutrition.
But the serious climate issues will not be limited to the tropics, the scientists conclude. During Western Europe's record heat wave of 2003, maize production fell by 30% in Italy and France, with wheat and fruit harvests declining by one-quarter. Three decades earlier, record heat in the Soviet Union disrupted the wheat harvest, causing a worldwide tripling of wheat prices an early foreshadowing of how local problems can ripple through a globalized agricultural economy.
"When all the signs point in the same direction, and in this case it's a bad direction, you pretty much know what's going to happen," Battisti said.
Per Pinstrup-Andersen, a Cornell University agricultural economist and World Food Prize laureate told Brandon Keim of the Wired, "As policymakers, as people, we tend not to deal with problems until they are very severe. As a society we must begin to take this seriously and that means a lot more adaptation."
Scientists must develop crops suited to Earth's new climate, Naylor and Battisti argue. Better techniques, such as highly efficient irrigation systems and spoilage-reducing harvesting methods, are also required. So are alternatives to fossil fuel-intensive fertilizers and pesticides.
But investment in agricultural research has waned in recent decades, they write, at precisely a time when modern food output is "insufficient to meet near-term food needs in the world's poorest countries, to say nothing of longer-term needs in the face of climate change."
Pinstrup-Andersen echoed their analysis. "Right now, the countries that should be investing in agricultural research are investing very little," he said. "This research will take a considerable amount of time to complete. We have time but we have to start investing now."
Those proscriptions are basic and relatively attainable. More controversial and complicated is reform to the global agricultural system.
"Two-thirds of all developing countries are net food importers," said Steve Suppan, a senior policy analyst at the nonprofit Institute for Agriculture and Trade Policy. In these countries, said Suppan, formerly agrarian economies were reorganized around service and manufacturing but promised riches failed to materialize, leaving nations both impoverished and unable to feed themselves.
Pinstrup-Andersen disagreed with Suppan's recommendation, saying that national food self-sufficiency would be expensive and disruptive, throwing isolated nations at the mercy of regional weather shifts. Instead, Pinstrup-Andersen recommended even more globalization, and harsh punishments for countries that turn protectionist.
The fates of these countries are uncertain unlike, said Naylor, the changing climate.
"With the temperature projections, there's no disputing where we're heading," she said. "We have to face reality."