Warming could tank corn production — study

Source: Chelsea Harvey, E&E News reporter • Posted: Wednesday, June 13, 2018

Corn crops — and global food security — could be at risk due to climate change, new research shows.

Rising temperatures may cause significant declines in the global production of the staple food crop, according to a study published yesterday in Proceedings of the National Academy of Sciences.

It’s the latest study to suggest that climate change may threaten some of the world’s most globally important crops — a major concern for food security in nations around the world. With a world population of nearly 10 billion projected by midcentury, scientists are increasingly preoccupied with global agriculture — and whether it will be able to feed all those mouths in the future.

Just a few weeks ago, an eyebrow-raising paper in Science Advances suggested that rising carbon dioxide concentrations could cause a decline in the nutritional quality of rice — a critical food source for billions of people around the world. Corn, wheat and rice together supply at least half the world’s dietary energy, according to the U.N. Food and Agriculture Organization. Global corn losses could potentially affect billions of people.

But that’s not the only bad news. The new study also suggests that a warmer world will also cause corn yields to become more variable from one year to the next, in addition to just being lower overall. This means the probability of major corn-producing regions experiencing a bad crop year all at the same time — an event that would significantly drive up corn prices around the world — substantially increases.

The researchers, led by Michelle Tigchelaar of the University of Washington, used global data on corn production to inform models of corn yields under different future climate scenarios.

Under 2 degrees Celsius of warming — the major target outlined under the Paris climate agreement — they found that corn yields declined to some degree in most places around the world, with the exception of a few sites in Western Europe and China. Under 4 C of warming, closer to a “business as usual” climate scenario, these declines became even more severe — with losses of up to 40 percent in many places around the globe, including the United States.

Even under the milder 2 C scenario, the risk of greater variability in corn yields — and potential shocks to the global corn market — also rises substantially.

The majority of the world’s corn supply is exported by just four countries: the United States, China, Brazil and Ukraine. Currently, the risk of all four countries experiencing an unusually bad year at the same time — that is, more than a 10 percent drop in yield in any given year — is close to zero. But under just 2 C of warming, the risk rises to 7 percent. And under 4 C, it soars to 86 percent.

Such an event could produce a tremendous global ripple, driving up corn prices around the world, the researchers suggest. Low-income households, which globally may spend a greater share of their income on staple foods, would likely be disproportionately affected.

A major caveat of the findings is that they don’t account for potential changes in precipitation patterns, which vary from one location to the next and could offset or exacerbate the effects of rising temperatures. But the authors suggest that, on a global scale, the effects of higher temperatures are expected to outweigh those of precipitation changes — and in highly managed agricultural systems, such as those common in the United States, Europe and China, irrigation may help offset some of those effects, as well.

While the corn study focuses only on temperature, another paper, also out yesterday in Proceedings of the National Academy of Sciences, takes a broader look at the impact of environmental changes on agriculture. It includes a comprehensive literature review of the effects of rising temperatures, higher carbon dioxide concentrations, precipitation changes and other environmental disturbances, examining 174 studies of nonstaple crops in 40 countries around the world.

The paper focuses on nonstaple vegetables and legumes, noting that numerous studies already suggest that staple food crops — including wheat, rice and corn — are likely to suffer global losses under future climate change.

Climate change may have a somewhat nuanced effect on many nonstaple crops, the review suggests. In cooler regions of the world, a warmer climate could actually give crops a boost. In warmer regions, the opposite is likely — studies based in the tropics and subtropics generally found that several degrees of warming would result in significant yield declines.

The paper also found that major declines in water availability would cause serious reductions in crop yields, while higher carbon dioxide concentrations could increase crop yields — although the researchers note that this boosting effect is likely to taper off after carbon dioxide levels reach a certain point.

The review highlights the complexity of the many climate variables acting on local agricultural systems. But it does suggest that certain current trends in climatic changes, including rising temperatures and an increased risk of water shortage in some regions, may put a strain on food crops.

And for the world’s biggest staple crops, including corn, the growing body of literature continues to indicate a net negative influence from climate change. This week’s paper is the latest, but hardly the only, in that vein — other research, including a major paper published last year, has suggested that rising temperatures may lead to significant losses not only in corn, but in wheat, rice and soybeans, as well.

In the absence of immediate, significant climate action, which would keep global temperatures below the 2 C threshold, the researchers note that breeding more heat-tolerant crops may be the only way to safeguard the global production of staple crops — which they warn is a “high-priority, but an as-of-yet unattained, goal” for corn.