Soy FACE: Technology for Understanding the Impact of Climate Change on Food Supply

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For people who live far from rising seas or melting glaciers, it can be difficult to maintain a sense of the consequences as the world’s climate changes in response to human activity. But for a team of U of I researchers interested in global food supply headed by crop scientist Stephen Long, the stakes are much clearer.

At issue for Long and colleagues is how changes in the composition of the earth’s atmosphere and the associated rise in average temperatures will affect the planet’s potential for producing food crops in the next fifty to eighty years. These changes, which are in motion now and would occur even if stringent restrictions on emissions were adopted tomorrow, include a fifty percent rise in the concentration of carbon dioxide in the surface layer of the earth’s atmosphere, a twenty percent increase in surface layer ozone, and a three to four-degree F rise in temperature.

Previous research has suggested that, overall, global food supply will remain nearly constant, despite significant changes in productivity for particular regions. The rise in temperature will depress the global productivity of the major food crops, but this is predicted to be cancelled by the fertilizer effect of rising carbon dioxide. Carbon dioxide is used by plants with sunlight energy to make carbohydrates and ultimately our food.

According to Long and his colleagues, however, these projections are unrealistically optimistic. They overestimate the benefit to crops of higher carbon dioxide levels, and they have ignored the negative impact of higher ozone levels. The studies these projections are based on are also questionable because they have been conducted in greenhouses, which are well known to be poor indicators of plant responses in the open air.

To make more accurate projections about future food supplies, Long and his colleagues have developed a system for elevating carbon dioxide and ozone to levels anticipated for the year 2050 in the field called Free-Air Concentration Enrichment. This system consists of seventy-foot rings of pipe that pump out different amounts of carbon dioxide or ozone to adjust the atmosphere for the crop growing within them. A computerized control and monitoring set-up allows the system to achieve the desired concentrations of gases remarkably well over the course of the growing season.

Long and his colleagues at the University of Illinois have examined soybeans and corn. Although theirs is the first to examine the effects of ozone, experiments elsewhere have looked at the effects of elevated carbon dioxide on other crops. One in Arizona examined wheat and sorghum, and another in Japan examined rice.

Collectively, these experiments have shown benefits from higher levels of carbon dioxide that are around fifty percent lower than greenhouse studies have projected. That’s like expecting an eight percent return on an investment and realizing only four percent. At the same time, the Illinois study of soybeans has shown a twenty percent yield loss in response to a twenty percent increase in surface level ozone, about what we can expect by the year 2050.

From of a crop science perspective, the shortfalls predicted by these experiments represent a call to action, a challenge to be met by breeding plants suited to the atmosphere of the future, or figuring out ways to bring more land into agriculture. From a broader perspective, they are another reminder that the climate change humans are now producing will pose complex problems for generations to come.