Record-breaking heat is threatening wheat and the global food supply

Our world is becoming hotter. This isn’t simply a matter of sweltering summer afternoons. It’s a complex, global shift that’s altering seasonal patterns, intensifying weather extremes like severe droughts and punishing heat waves, and consequently affecting our food supply.

A freshly published study led by a dedicated team at the Friedman School of Nutrition Science and Policy at Tufts University brings these issues into sharp focus. 

The study centers on the increased likelihood of extreme temperatures that could devastate crop yields, specifically focusing on the wheat-producing regions of the U.S. and China.

“Imagine heat waves that used to happen once every hundred years in 1981,” explained study lead author Erin Coughlan de Perez. “Our data shows that these are now likely to happen once every six years in the Midwestern U.S., and once every 16 years in Northeastern China.” 

Preparing instead of reacting is the key

This forecasts a range of conditions for which we must prepare, even though we have yet to experience them. “The historical record is no longer a good representation of what we can expect for the future,” said Coughlan de Perez.

Published in the journal Climate and Atmospheric Science, the paper warns that we live in a changed climate, and people are underestimating current day possibilities for extreme events.

The research pivots on a telling fact from the Intergovernmental Panel on Climate Change: the average global surface temperature in the last decade was 1.1 degrees Celsius higher than it was between 1850 and 1900.

How the study was conducted

To examine the food simply impacts of this increase on our risk of extreme weather, Coughlan de Perez and her team have meticulously collected a massive ensemble of seasonal forecasts from the past 40 years. These were used to generate thousands of potential temperature and rainfall variations, essentially painting a picture of all the weather outcomes that could have occurred in any given year.

Their unique method, dubbed the Unprecedented Simulated Extreme Ensemble or UNSEEN approach, allowed the researchers to estimate the likely frequency of extreme temperatures that exceed critical growth thresholds for wheat.

Let’s look at winter wheat crops. They kick off their growth in the fall and get harvested the following summer. High spring temperatures, when the plant is flowering, can impact the wheat’s development. 

At temperatures over 27.8 degrees Celsius (about 82 degrees Fahrenheit), the plants start to experience heat stress. Beyond 32.8 degrees Celsius (about 91 degrees Fahrenheit), vital enzymes in the wheat start to deteriorate.

“In the Midwest, we used to witness seasons with an average of maybe four or five days exceeding this enzyme breakdown threshold – it was quite uncommon,” said Coughlan de Perez. “However, our research revealed potential alternate realities of today’s climate, showing up to 15 days above this threshold, which would likely cause substantial damage.”

Extreme heat normally coincides with extreme drought

To make matters worse, record-breaking heat often coincides with record-breaking drought. These two threats combined could drastically reduce the growing season. 

Given that the U.S. and China are substantial grain producers for the world, simultaneous crop failures or concurrent failure with other staple crops could profoundly impact global food prices and availability.

The study’s results hint that we’ve been fortunate in these regions in recent years. While weather has an element of randomness, akin to rolling a six-sided die, these areas have been consistently “rolling” low numbers, experiencing cooler weather than they could have. 

However, climate change has effectively “changed the die,” raising the highest number. Consequently, these regions have yet to experience the worst of what could occur, and may not be adequately prepared.

“My hope is to make people aware that their die has changed,” said Coughlan de Perez. “You can roll something extremely harsh. Perhaps you won’t roll an eight for some time, but it’s essential to establish plans for when that happens.”

Predicting the future by studying the atmosphere

Furthermore, the researchers pinpointed regional and global atmospheric circulation patterns that could trigger severely hot and dry events. They even highlight a worst-case scenario where both the U.S. and China’s wheat production suffer in the same season. This information could prove crucial in crafting climate adaptation plans and ensuring stakeholders are prepared for these unprecedented future events.

“I think, with climate change, we’re suffering from a failure of imagination,” said Coughlan de Perez. “If we’re not envisioning the kind of extremes that could occur, then we won’t be ready for them.” She strongly believes we don’t need to be caught off guard. “We can use tools at our disposal to try to understand what’s possible and be ready when it happens.”

More about wheat 

Wheat is one of the major food crops of the world, serving as a staple diet for more than a third of the global human population, according to the Food and Agriculture Organization. Its diverse varieties allow it to be grown in a range of geographic regions, from the plains of the U.S. Midwest to the steppes of Russia and the fields of China. 

Wheat supplies about 20% of the food calories for the world’s population. Consequently, disruptions to wheat harvests can have profound impacts on food security, availability, and prices, affecting human nutrition and potentially leading to social and economic instability.

Climate change, however, poses significant risks to the sustainability of wheat production. Rising temperatures, changing rainfall patterns, and increased frequency and intensity of extreme weather events like heatwaves and droughts are all aspects of climate change that can adversely impact wheat crops.

High temperatures, particularly during the critical flowering stage, can significantly reduce wheat yields. Heat stress during this period can lead to lower grain numbers and smaller grain sizes. 

As noted in the study led by Erin Coughlan de Perez, the temperatures at which wheat plants start to suffer from heat stress and critical enzymes begin to break down are 27.8 degrees Celsius (about 82 degrees Fahrenheit) and 32.8 degrees Celsius (about 91 degrees Fahrenheit), respectively.

Impact of climate change on wheat production

Moreover, research indicates that climate change may exacerbate the incidence of pests and diseases that affect wheat, adding to the challenges facing wheat production. Changing weather patterns can also disrupt the usual planting and harvesting cycles, causing further uncertainties for farmers.

A study published in Nature Climate Change in 2017 suggests that if global temperatures increase by 2 degrees Celsius, wheat yields could fall by 6% on average globally. This decline may not seem significant, but considering the billions of people who rely on wheat as a staple food, the impact could be substantial.

To mitigate these impacts, farmers and researchers are exploring various adaptation strategies. These include developing new, heat-resistant wheat varieties, altering planting and harvesting schedules to avoid periods of likely heat stress, and improving irrigation practices to cope with changing rainfall patterns.

Global societal action is needed

However, while these adaptations can help, they may not entirely offset the potential impacts of climate change on wheat production. As such, broader societal action to limit global warming is essential to ensure the long-term sustainability of wheat and other critical food crops. 

Moreover, policy measures are needed to support farmers in adopting sustainable practices and to provide safety nets for those affected by crop failures due to extreme weather events.

In conclusion, the challenges posed by climate change to wheat production are substantial but not insurmountable. With careful planning, scientific innovation, and global cooperation, it is possible to safeguard this vital crop for future generations.

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