grain

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Climate change may dramatically reduce wheat production, study shows

Vara Prasad, professor of crop ecophysiology and director of the USAID Feed the Future Sustainable Intensification Innovation Lab at Kansas State University, is part of a collaborative team that found wheat yields are projected to decrease by 6 percent for each degree Celsius the temperature rises if no measures to adapt to extreme weather fluctuations are taken.

Based on the 2012-2013 wheat harvest of 701 million tons worldwide, the resulting temperature increase would result in 42 million tons less produced wheat — or a loss of nearly one-quarter of the current wheat production.

“It’s pretty severe,” Prasad said. “The projected effect of climate change on wheat is more than what has been forecast. That’s challenging because the world will have to at least double our food supply in the next 30 years if we’re going to feed 9.6 billion people.”

Prasad and colleagues published their study, “Rising temperatures reduce global wheat production,” in a recent issue of the scientific journal Nature Climate Change. The study was supported through the Kansas Wheat Commission and the Kansas Wheat Alliance, two organizations seeking ways to increase wheat yield.

For the study, researchers systematically tested 30 wheat crop models against field experiments from around the world that were conducted in areas where the average temperature of the growing season ranged from 15 to 32 degrees Celsius. The models accounted for planting dates, planting rates, temperatures and other crop management factors.

With the models, researchers were able to look at the effects of temperature stresses on wheat and predict future changes based on temperature changes.

Researchers found that the effects from climate change and its increasing temperatures on wheat will be more severe than once projected and are happening sooner than expected. While Prasad said increases in the average temperature are problematic, a bigger challenge is the extreme temperatures that are resulting from climate change.

“Extreme temperature doesn’t only mean heat; it also means cold,” Prasad said. “Simply looking at the average temperature doesn’t really show us anything because it’s the extremities that are more detrimental to crops. Plants can handle gradual changes because they have time to adapt, but an extreme heat wave or cold snap can kill a plant because that adjustment period is often nonexistent.”

Researchers also found that increasing temperatures are shortening the time frame that wheat plants have to mature and produce full heads for harvest, resulting in less grain produced from each plant.

“It’s like having one minute to fill a tall glass with water. Under optimal conditions, we can fill that glass pretty well,” Prasad said. “But now we’re factoring in extreme temperatures that are affecting the growing window and the grain size. So it becomes like trying to fill that same glass, but now we only have 40 seconds to do it and the faucet is running slower.”

Currently, Prasad and colleagues at Kansas State University, in collaboration with the university’s Wheat Genetics Resource Center, are using growth chambers and heats tents to quantify the effects of temperature. The data will help in refining the crop models so that they can be more accurate in predicting wheat responses.

Their work will help scientists develop more robust models that can help farmers globally select more weather-tolerant and resilient wheat varieties based on their location. Additionally, farmers can determine the optimal planting date to avoid stress and minimize possible exposure to extreme weather events, such as heat and cold snaps, during the growing season. More

 

Grain Harvest Fact Sheet

With grain providing much of the calories that sustain humanity, the status of the world grain harvest is a good indicator of the adequacy of the food supply.

Lester Brown

More than 2 billion tons of grain are produced each year worldwide, nearly half of it in just three countries: China, the United States, and India.

Corn, wheat, and rice account for most of the world’s grain harvest. Whereas rice and most wheat are consumed directly as food, corn is largely used for livestock and poultry feed, and for industrial purposes.

Global grain consumption has exceeded production in 8 of the last 14 years, leading to a drawdown in reserves.

Population growth is the oldest source of increasing grain demand. In recent years, the annual growth in grain use has doubled, largely a result of increased use for fuel ethanol and livestock and poultry feed.

In 2013, the United States harvested more than 400 million tons of grain. Of this, 129 million tons (30 percent) went to ethanol distilleries.

Rising yields are the key to expanding the grain harvest as there is little unused cropland. Since 1950, over 93 percent of world grain harvest growth has come from raising yields.

The global grain area planted per person has shrunk from about half an acre (0.2 hectares) in 1950 to a quarter acre (0.1 hectares) in 2013.

At 10 tons per hectare, U.S. corn yields are the highest of any major grain anywhere. In Iowa, some counties harvest up to 13 tons per hectare.

Global average grain yields more than tripled from 1.1 tons per hectare in 1950 to 3.5 tons per hectare in 2013. However, yield growth has slowed from 2.2 percent a year between 1950 and 1990 to 1.4 percent in the years since.

In France, Germany, and the United Kingdom, wheat yields have been flat for more than a decade. The story is similar for rice in Japan and South Korea.

World fertilizer use climbed from 14 million tons in 1950 to 181 million tons in 2013. But in many countries, fertilizer use has reached diminishing returns.

Since 2007, the world has experienced three major grain price spikes. The U.N. Food Price Index indicates that grain in 2014 was twice as expensive as in 2002–04.

Rising global temperatures threaten the world’s major food crops; the “rule of thumb” is that each 1-degree-Celsius rise in temperature (1.8 degrees Fahrenheit) above the growing season optimum can cut productivity by at least 10 percent. More