From afar, the three young men tramping through a corn field look like Midwestern farm boys checking their crop. And a fine crop it seems 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 - point to streaked, yellowing leaves on some of the corn plants. "You're definitely seeing some damage," says Tiago Tomaz, a biochemist from Australia.
These fields 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 bigger question is: What can be done to make crops more resilient? 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 suggests 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. 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.
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.
Gorka Erice, a plant biologist from the Basque Country of Spain, fired up a $75,000 machine he was toting on his back and started taking measurements of how fast photosynthesis was occurring in the corn leaves. Two colleagues - Chris Montes, an American, and Tomaz, the Australian - followed just behind him. They sliced neat circles of tissue from the leaves Erice had just measured, then dropped some of them into a tank of liquid nitrogen, freezing the leaves at minus 340 degrees Fahrenheit for later molecular analysis in the laboratory. The full results of this summer's labours will not be known for months. But already, it is obvious to the scientists that some varieties of corn resist ozone better than others. Similarly, they have found varieties of soybeans that grow especially well in high carbon dioxide levels. And they are starting to ask similar questions about plants like tomatoes, peas and strawberries that are consumed more directly as food.
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.
The ultimate hope is to develop crop varieties able to stand up to all the stresses global warming is likely to bring.
© 2014 The New York Times
