Growing Grain in a Warming World

As sobering as they are, Long and other experts believe that the FACE results paint a rosier picture than what we really should expect if global warming continues. “It is also important to produce realistic conditions with regard to insects, pests, fungal disease exposure, and so on, and even the FACE experiments are likely idealized in these aspects and thus optimistic,” according to Kevin Trenberth of the Boulder, Colorado-based National Center for Atmospheric Research, via e-mail.

According to Long, the significance of the FACE results is clear: a food supply crisis will come sooner than previously predicted. The earlier prediction, based on the 2001 IPCC report, is that worldwide food production will have increase five to fifteen percent by 2050, but then decline.

The IPCC’s 2001 and 2007 projections, based on complex mathematical models, concluded that over the next hundred years global surface temperatures will increase. The effects of this warming are predicted to be enormous: rising sea levels will reshape coastlines, plant and animal ranges will move toward the poles, species will go extinct, and extreme climatic events like droughts and floods will increase in frequency. While agriculture in temperate latitudes is expected to prosper, crops grown in the tropical climes are projected to decrease.

The agricultural experts who are involved in updating the IPCC impacts report disagree with Long and say that the IPCC projections for the first half of this century do not need to be revised in light of his results. Penn State’s Easterling, his colleague Cynthia Rosenzweig of Columbia University, and other IPCC contributors wrote a rebuttal of Long’s analysis.

Rosenzweig notes that most crop projections already assume that the big yield increases predicted by the greenhouse studies won’t hold up in real-world conditions. “Most [crop models] use lower values already…because we realize we are making an estimate for farmer’s fields,” she said.

Besides, factors that have nothing to do with carbon fertilization – such as fertilizer use, technology and market prices – are much more likely to influence future crop yields, according to Easterling and Rosenzweig. “The variation in environmental conditions, socioeconomic trends and market interactions will have more impact than the FACE/non-FACE difference,” said Rosenzweig.

The biggest worry, Rosenzweig said, is that farmers in the U.S. and Canada may not be able to pick up the slack if, as predicted, their counterparts in Africa are subjected to increasing droughts and lack the resources to adapt. The “global food system in trade and donation” could be dramatically affected, triggering a food supply crisis.

Future rainfall patterns – and farmers’ abilities to adapt to them – will be crucial factors in determining how severe that inevitable food crisis will be. “As climate changes there is increased risk of drought, and then heavier rains. Gentle or moderate rains are most beneficial for agriculture,” said Trenberth, the Colorado researcher.

In the U.S., Midwestern states are likely to experience more extreme climatic events – including droughts and torrential rains – than modelers previously predicted, according to a new climate model developed by researchers at Purdue University’s Climate Research Center.

The cost of growing crops is also likely to increase, since the expense of expanding irrigation systems has never been incorporated into the IPCC models, according to Anthony Fisher, an agricultural economist at the University of California at Berkeley.

“Agriculture is a human system, and there will be adaptation. Farmers will figure out the new landscape,” noted Rosenzweig. “But adaptation may not [always] be possible, complete, or cheap.”

For further information, check out these links:
Union of Concerned Scientists: summary of 2001 IPCC
Number Watch: global warming information