Testing food production in face of global warming

Crops grown in environment designed to mimic future conditions have serious deficiencies of nutrients.

From afar, the three young men tramping through a corn field at Savoy, Illinois, looked like Midwestern farm boys checking their crop. And a fine crop it seemed to be, with plump ears hanging off vibrant green stalks. But as they edged deeper into the field, the men — actually young scientists, not farmers — pointed to streaked, yellowing leaves on some of the corn plants. “You’re definitely seeing some damage,” said Tiago Tomaz, a biochemist from Australia.

The injured leaves signaled trouble down the road, and not just for a single plot of corn a few miles from the main campus of the University of Illinois. By design, the scientists were studying the type of damage that could put a serious dent in the food supply on a warming planet.

The fields here are among a handful of places in the world where researchers are trying to mimic the growing conditions expected to arise decades in the future as the air fills with heat-trapping gases and other pollutants from human activity. A network of pipes sprays extra carbon dioxide and a corrosive pollutant, ozone, into the air. Lamps and other equipment mimic future droughts and heat waves.

The work has been going on in some form for nearly a decade, and the answers so far have been worrisome. Earlier this year, for instance, researchers at Harvard and elsewhere pooled data from the Illinois project with findings from scientists in three other countries. In a high-profile paper, the experts reported that crops grown in environments designed to mimic future conditions have serious deficiencies of certain nutrients, compared with crops of today.

The Illinois researchers are trying to move past just documenting the potential trouble, though. The bigger question is: What can be done to make crops more resilient? That has lately become an urgent topic. For decades, many climate experts were relatively sanguine on the issue, thinking that warming in frigid northern countries would benefit crops, helping to offset likely production losses in the tropics. Moreover, some research suggested potentially huge crop gains from a sort of counterintuitive ace in the hole: the very increase in carbon dioxide that is causing the planet to warm.

Plants pull carbon dioxide out of the air and use sunlight to turn it into energy-dense sugars, and research done in the 1980s and 1990s suggested that higher carbon dioxide levels in the future might give crops a major boost. But that work was done under artificial conditions, such as in greenhouses. Researchers in various places, including at the University of Illinois, saw a need for tests under more real-world conditions.

They can do only so much, using their best guesses as to what future climate conditions and pollution levels will be. “We know it’s not a perfect simulation of the future, but we believe it’s letting us get a jump start on creating solutions,” said Andrew D.B. Leakey, one of the University of Illinois scientists leading the work.

The tests so far have confirmed the beneficial “CO2 fertilisation effect,” as it is known. But in field conditions, the boon to the crops was not as great as in earlier greenhouse experiments, and probably not enough to offset the heat and other stresses of a warmer planet. “It’s there, it’s real, but the question is, how much is it going to help?” Leakey said.

Other research in recent years suggested that rising temperatures in some of the world’s most important growing regions were already cutting into potential grain production, compared with what the yields would likely be in the absence of global warming. That problem may well have contributed to an upward spiral in grain prices a few years ago that led to food riots and destabilised the governments of some poor countries.

Urgent warnings

The accumulating evidence of risk prompted a sharp warning earlier this year from the Intergovernmental Panel on Climate Change, a United Nations body, which said that a reliable food supply could no longer be taken for granted on a hotter planet. “Negative impacts of climate trends have been more common than positive ones,” the panel declared in a report released in Berlin in April.

At the same time, the panel pointed out the enormous potential for agriculture to adapt to climatic change, with shifts in farming practices and with improved crop varieties. The Illinois scientists aim to test that potential.

Led by Leakey and Elizabeth A Ainsworth, a scientist with the United States Agriculture Department, the researchers have created an unusual blend of climate science, agriculture and modern genetics to study possible routes to a more resilient food supply.

One recent day, as the summer sun beat down,  Leakey led a tour through 80 acres of corn, soybeans and millet. Pipes, hoses and electrical cables snaked through the plots, and high-technology equipment hummed inside garden sheds. The hoses were spraying gases into the air — carbon dioxide over the soybeans, to see how they would respond to the concentrations expected in the future, and ozone over some of the plots of corn.

High in the atmosphere, ozone shields the planet from some of the sun’s damaging radiation. But at ground level it is a pollutant, forming from chemical reactions involving certain emissions from cars and power stations. It is a corrosive form of oxygen that attacks both plants and people’s lungs, and many experts fear ground-level ozone will increase as the world gets hotter and more polluted.

In recent years, leading scientists have called for a much more intense focus on ozone, noting that it seems to be cutting world food production already compared with what would otherwise be possible. Moreover, it may be an easier pollutant to control than carbon dioxide.

“We could actually increase the food supply quite significantly if we paid attention to this,” said Denise L Mauzerall, a researcher at Princeton University who has studied the issue.The Obama administration is under court order to by late this year come up with a potentially costly plan for reducing ozone, mostly to benefit human health, but with likely benefits for crop production, too. However, reducing ozone is not the only possible strategy for helping crops. Developing plants resistant to its effects would be another approach, and that is a major focus at the University of Illinois.

The preliminary findings suggest a strategy for securing the food supply. If the researchers can figure out the fundamental genetic reasons that some plants do better than others in difficult conditions, those insights could become crucial for plant breeders. “Plant breeding is the art of picking winners and avoiding losers, so you have to know what to look for,”  Ainsworth said.

The ultimate hope is to develop crop varieties able to stand up to all the stresses global warming is likely to bring. Given the problems already occurring in the global food system from climatic disruption, Ainsworth added, “building resiliency in agriculture is a topic that’s on everybody’s mind.”

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