Not in Kansas anymore? EPA’s pessimistic wheat forecasts

Published October 1, 2000

From time to time, we’ve looked at some of EPA’s new “State and Local Climate Change Outreach Kits,” released this year as a public service. In fact, these kits seem to do the public a pronounced disservice, painting a misleadingly bleak picture of our CO2-enhanced future.

In its Kansas materials, EPA tells us that during the next century, “Wheat yields could rise by 15 percent or fall by 15 percent, depending on how climate changes and the extent to which the temperature tolerance levels of the crop are exceeded.”

For a state that produced a record 492.2 million bushels of wheat in 1997, enough to make 35.9 billion loaves of bread, that drop might be a tough row to hoe. But our survey of the literature on rising CO2’s effect on plants suggests wheat in Kansas (and elsewhere) should a) grow larger and healthier, b) produce more yield, and c) become more water-use efficient and tolerant to drought.

Yet another article comes to us from Australia, where Masle grew wheat in well-ventilated greenhouses matched for temperature and humidity but varying atmospheric CO2 concentrations. One greenhouse had a natural CO2 level during the day and 420 ppm at night; the other, 900 ppm day and night.

“Elevated [CO2] has profound effects on cell division and expansion in developing wheat,” the authors reported. Indeed, it produced a 52 percent to 93 percent increase in total dry weight and a 39 percent to 82 percent increase in leaf area. Increased CO2 led to a greater number of tillers, an increase in the sugar content of the leaves, and an increase in the growth rates of individual leaves with accelerated cell division rates.

If all that is not good enough, the additional CO2 also led to an increase in water-use efficiency. Masle concludes: “The data presented here demonstrate that elevated [CO2] has profound effects on leaf development, expansive growth, and anatomy in wheat.” Amen!

In a second recent article, Pinter and colleagues remind us that sometimes the equipment used in elevated CO2 experiments can alter microclimate in ways that lead to an underestimation of the effects of CO2 on wheat yields.

Blowers that inject CO2 into plots create an artificial breeze at night that disrupts the near-surface stability, drawing in warmer air from above. That decreases dew that could be made available to the plants and increases the transpiration rates.

Pinter originally found a 10 percent increase in wheat yield for wheat exposed to 550 ppm atmospheric CO2, compared with wheat at natural levels. “We now believe that this figure was probably an underestimate of the true CO2 effect that might have been observed during the first two seasons.” Corrected yields showed a 15 percent increase for the 200 ppm rise in CO2.

With such a bountiful harvest in store, farmers in the sunflower state may find themselves echoing Dorothy’s prophetic words: “I don’t think we’re in Kansas anymore.” As for EPA, its materials should reflect optimism rather than equivocation.

Robert C. Balling Jr., Ph.D. is director of the Laboratory of Climatology at Arizona State University and coauthor of The Satanic Gases.


Masle, J. 2000, The effects of elevated CO2 concentrations on cell division rates, growth patterns, and blade anatomy in young wheat plants are modulated by factors related to leaf position, vernalization, and genotype. Plant Physiology, 122, 1399-1415.

Pinter, P.J., Jr., et al., 2000. Free-air CO2 enrichment (FACE): Blower effects on wheat canopy microclimate and plant development. Agricultural and Forest Meteorology, 103, 319-333.