Heat is making crop harvests wildly unpredictable

Walk into a grocery store today and you may find familiar foods looking less predictable. From corn chips to tofu, climate change is quietly reshaping what fills our plates. Scientists are warning that it is not just about fewer crops, but about harvests becoming wildly unstable.

A global study led by the University of British Columbia shows that hotter and drier conditions are making food production swing more dramatically.

These shifts ripple through the economy, driving higher prices, creating financial stress for farmers, and leaving vulnerable communities facing hunger.

Heat makes crops unstable

The study, published in the journal Science Advances, tracked three major crops: corn, soybean and sorghum.

The researchers found that for every degree of warming, year-to-year yield variability jumps by 7 percent for corn, 19 percent for soybeans and 10 percent for sorghum.

Earlier studies mostly measured declining average yields. This research spotlights something equally dangerous: instability. For many farmers, that instability determines whether they survive another season or face ruin.

“Farmers and the societies they feed don’t live off of averages – they generally live off of what they harvest each year,” said Dr. Jonathan Proctor, assistant professor at UBC and lead author of the study.

“A big shock in one bad year can mean real hardship, especially in places without sufficient access to crop insurance or food storage.”

Rising disaster risk

The numbers highlight how warming multiplies risks. At two degrees hotter than today’s climate, soybean failures that used to occur once a century could strike every 25 years.

Corn failures would shift from once every hundred years to every 49, while sorghum failures would occur every 54 years.

Unchecked emissions push the timeline further. By 2100, soybean failures could arrive as often as once every eight years. The danger is greatest for farmers in Sub-Saharan Africa, Central America and South Asia, where rain-fed farming and weak financial support leave little room to absorb shocks.

Yet even wealthy regions are not immune. In 2012, a heatwave and drought in the U.S. Midwest cut corn and soybean yields by a fifth, costing billions and triggering a 10 percent spike in global food prices.

Heat and dryness worsen crops

The researchers found that it is not just heat alone but its overlap with dry soil that explains these swings. Using global harvest records along with climate data from satellites, models and weather stations, they pinpointed the twin stressors.

“A key driver of these wild swings? A double whammy of heat and dryness, increasingly arriving together,” said Dr. Proctor.

Hot weather dries the soil, which in turn amplifies heat. This vicious cycle hits plants hard, especially during sensitive phases like pollination.

“If you’re hydrated and go for a run your body will sweat to cool down, but if you’re dehydrated you can get heatstroke,” said Dr. Proctor. “The same processes make dry farms hotter than wet ones.”

Even short dry spells during high heat can devastate crops, especially soybeans and sorghum, where the overlap of heat and dryness drives much of the volatility.

Irrigation and its limits

The study shows that irrigation can reduce these risks, but only if water is available. Many of the regions most vulnerable already face water stress or lack infrastructure for large-scale irrigation.

That means the solution cannot rely on water alone, especially as water demand grows with rising populations, expanding cities, and shifting climate patterns.

In many parts of the world, aquifers are already being depleted faster than they can naturally recharge, adding another layer of uncertainty to future farming.

Even in wealthier nations, competing demands between agriculture, households, and industry often limit how much water farmers can access during droughts.

Addressing the root cause

The researchers recommend stronger safety nets to help farmers survive difficult years, alongside investment in heat- and drought-resistant crop varieties that can better withstand extreme conditions.

The experts also highlight the importance of better soil care, such as practices that improve water retention and reduce erosion, and the role of advanced forecasting systems that give farmers more time to prepare for upcoming heatwaves or dry spells.

These steps can soften the blow, but they are not enough on their own. Ultimately, the researchers emphasize that the most reliable and far-reaching solution is cutting the emissions driving global warming.

Without addressing the root cause, they warn, adaptation measures will always remain partial and temporary.

“Not everyone grows food, but everyone needs to eat,” said Dr. Proctor. “When harvests become more unstable, everyone will feel it.”

The study is published in the journal Science Advances.

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