Agriculture

There are many uncertainties

It is very difficult to predict how crops will react to changing climate because there are many unpredictable influences:

• At what critical points in the growing season heat waves and rain will occur
• How much more carbon dioxide will we will produce
• How much of human-generated CO₂ stays in the atmosphere
• How plants will react to increased CO₂

"When you're dealing with climate change predictions, the uncertainty is large," said University of Illinois plant biology professor Carl Bernacchi. "It's not quite as simple as temperature and precipitation."

The growing season will lengthen

The Illinois State Water Survey reports that the growing season in Illinois ranges from 160-190 days. Meteorologist Jim Angel notes that the average last freeze date, normally occurring between April 7 and April 28, seems to have shifted five to ten days earlier over the last few decades.

The Union of Concerned Scientists predicts that the growing season may lengthen by three to six weeks by the end of the century.

Crop prices will fall dramatically, then increase

The IPCC predicts that worldwide agricultural prices will change dramatically as our climate changes.

• Increases of up to 3.6 degrees Fahrenheit will mean a 10-30% drop in agriculture prices.
• Temperature change of 3.6 to 5.4 degrees mean that agriculture prices could fall as much as 10% or rise as much as 20%.
• A 5.4- to 9-degree change could raise crop and livestock prices by 10-40%.

Corn yields will increase, then decrease

Many conflicting ideas exist about what will happen to various crops. The general consensus is that corn will initially benefit from small degrees of warming, but will suffer at higher temperatures. Illinois temperatures are below the maximum temperature range for growing corn, but corn is very sensitive to drought and heat waves during a phase called tasseling, when the corn ears blossom.

Various thoughts about the effects of heat on corn include:

• University of Illinois professor Donald Ort predicts that corn will tolerate climate change much better than soy.
• University of Illinois Carl Bernacchi also predicts that corn yields will increase with warming, but cautions that a dry spell during tasseling can be fatal. Corn already requires more water than falls during the growing season, he explained.
• Bernacchi also explained that researchers are working very hard to make corn more resistant during its tasseling period.
• David Lobell and Gregory Asner conducted a study in 2003 that showed that every 1.8 degree Fahrenheit temperature increase would decrease both corn and soy yields by 8.3%.
• The optimum temperature range for corn to reproduce is 64 to 72 degrees; crops begin to fail at 95-degree temperatures, but we don't know how long they need to be exposed before failure.

The IPCC estimates the effects of specifc temperatures for corn production at mid- and high-lattitudes, such as Illinois.

• A 1.8 degree Fahrenheit increase will boost yields by 10%.
• A 3.6-degree change would negate the positive effects and we would see no change in crop yields.
• A 5.4-degree increase would reduce yields by about 5%.
• 7.2 degrees of change would mean about an 8% reduction in production.
• The effects begin to level off after this: We see a 9% decrease for a 9-degree change, and a 10% decrease for a 10.8-degree increase.

Soybean yields are unpredictable

Despite the uncertainties surrounding the effects for corn, our knowledge of what might happen to soybean crops in a changing climate is even more uncertain.

What we can say about soybean crops:

• Soy can withstand higher temperatures than corn.
• Their optimum reproduction temperature is 72 to 75 degrees; reproduction fails at 102 degrees.
• University of Illinois professor Lisa Ainsworth explains that soy undergoes a process called C3 photosynthesis, which will benefit from increased carbion dioxide and may lead to yield increases with increased CO₂ emissions. (Corn undergoes C4 photosynthesis, which does not benefit from increased CO₂.)
• However, the negative effects of increased ozone in the air may negate the positive effects of increased CO₂.
• Professor Carl Bernacchi says that soybean response to climate change is very unpredictable.
• David Lobell and Gregory Asner undertook a study in 2003 which suggested that every 1.8-degree temperature increase could hurt soybean yields by 8.3%.
• Soy may see a 2.5% increase in temperature changes of up to 2.2 degrees and a 17% increase with a 3.6-degree change, but temperatures higher than this will likely begin to show decreases.

The University of Illinois is currently conducting a major research venture called SoyFACE (Soybean Free Air Concentration Enrichment) to examine the effects of both carbon dioxide (CO₂) and ozone (O₃) for corn and soy crops.

Hardest hit: small farms, specialty crops, southern Illinois

Smaller farms, less able to absorb losses and more vulnerable to yearly variations, will be more prone to suffer from the negative impacts of climate change.

The southern part of the state, which is closer to the maximum temperature range for many crops, will also be disadvantaged. "We're at a place where we can grow crops at higher temperatures than we do," said Lisa Ainsworth, professor of genomic biology at the University of Illinois. These thresholds will breached last in the northern parts of the state.

Smaller yields and less financial incentive to adapt methods to a new climate will put small, specialty crops more at risk. In addition, many fruit crops such as apples, pears, plums, and peaches rely on bees and other pollinators to reproduce. However, changing temperatures may cause pollinators to move, causing a disconnect between these plants and the pollinators they rely on.

Livestock: few initial effects, then declines

Temperature changes of up to 3.6 degrees Fahrenheit may have little effect, or positive effects, on livestock yields. However, increases between 3.6 and 5.4 degrees are predicted to cause moderate losses in swine and cattle.

But maybe we can adapt

Many scientists believe that growers will adapt to changing conditions before climate change becomes a problem.

"Whenever we're faced with a problem in agriculture, someone tries to solve it," said plant biology proefssor Carl Bernacchi. He explained that the farming industry is so important that people are willing to dedicate significant time and energy to ensure its success.

Some scientists believe that growers will use genetic modification to help their crops adapt; this process may be so successful that current predictions for the future of crops will become irrelevant. "Technical advances and trends in markets will moderate the influence of climate change on both crops and livestock," reported the Union of Concerned Scientists.

However, Don Wuebbles, atmospheric sciences professor at the University of Illinois, contends that the picture may not be so simple, nor the problems so easily mitigated. Wuebbles explains that uncertainty regarding the amount of climate change may make adaptation difficult. "There has been increasing recognition that the overall response may be more complex (than originally thought)," explained Wuebbles.

The quick gauge

• We are faced with many uncertainties.
• Corn yields will likely increase, then decrease.
• We are more unsure about soy.
• The growing season will probably lengthen significantly.
• Crop prices will likely fluctuate with time.

Agricultural production in the Midwest is critically dependent on the weather."

- Don Wuebbles, professor of atmospheric sciences at the University of Illinois

"Technical advances and trends in markets will moderate the influence of climate change on both crops and livestock."

• The Union of Concerned Scientists