Climate

Heat Waves And Drought Are Already Having A Devastating Impact On Important Crops

CREDIT: AP Photo/Nati Harnik

A dry field of corn during the 2012 drought in the United States.

For all the wrong reasons, the summer of 2012 was a historic one for the American Midwest. Plagued by the worst drought the region had seen in decades, as well as weeks of high temperatures, one of the country’s most productive agricultural regions faced massive shortages in its annual corn crop, driving corn prices to a record high.

A new study, published Wednesday in Nature, argues that the American Midwest isn’t the only place to see staple crops like corn suffer in the face of extreme weather events. The paper, written by a team of geographers from the University of British Columbia, analyzed the effects that extreme temperatures, floods, and droughts have had on the last five decades of crop harvests. What they found was that both droughts and heat waves had a marked impact on a country’s crop production, cutting into cereal crops like wheat, rice, and maize by 10 percent and 9 percent respectively. Floods and cold spells, the study found, had no impact on crop production.

Perhaps surprisingly, the study also found that the damages to crops were greater in developed countries than developing ones, running counter to the idea that developed countries can afford technological fixes to buffer crops against things like drought and extreme heat. Cereals in North America, Europe, and Australia, for instance, suffered 19.9 percent decreases in production during droughts, compared to a 12.1 percent decrease in Asia and a 9.2 percent decrease in Africa.

The study’s authors hazarded a few reasons for this distinction, starting with the fact that in developing countries, farmers often tend to rely on smaller, more diverse farm plots, compared to the larger monocropping systems common in developed countries. On a farm with only one main crop — maize, for instance — drought has a uniform impact, whereas on farms with a more diverse menu of crops, drought might impact some crops while leaving others unaffected. Small-holder farmers in developing countries also tend to already employ risk-minimizing strategies on their farms, a practice that makes them more resilient to potential shifts in weather and climate.

Global warming is expected to increase the likelihood of heat waves around the world, and could also contribute to more droughts in some regions. Those changes will occur as the world’s population continues to grow — likely reaching 9 billion by 2050 and placing more stress on farmers to provide food under increasingly variable conditions.

“We don’t think about it much, but rice, wheat, and maize alone provide more than 50 percent of global calories,” Navin Ramankutty, an author of the study, told the New York Times. “When these grain baskets are hit, it results in food price shocks, which leads to increasing hunger.”

Farmers have already seen an uptick in the damage to crops caused by extreme weather events in recent decades — according to the study, the effect of drought on crop production has worsened since 1985, something the authors speculate could be due to a combination of more intense droughts, increased vulnerability to droughts, and changes in drought and loss reporting. Overall, between 1964 to 2007, the study estimates that a total of three billion tons of cereal crops were lost due to drought and heat waves.

In the United States, cereal crops occupy a huge amount of farm acreage, with corn and wheat registering as the first and third most common field crop in the country, respectively. The majority of the country’s corn crop is grown throughout the Midwest, which, according to the 2014 National Climate Assessment, is expected to experience more heatwaves, droughts, and floods in the future due to climate change. The United States’ wheat crop is primarily grown in the country’s northern states — North Dakota, South Dakota, and Montana — as well as throughout the Great Plains. Like the Midwest, the United States’ Great Plains are expected to become dramatically hotter as the climate changes.