Three Times a Day: How Climate Change Is Already on Your Plate

I was on the A train when it happened. We had come to a halt in a dark tunnel shortly after leaving Penn Station. I struck up a conversation with a well-dressed gentleman beside me. With his stylish briefcase and crisp clothes, he looked like a poster child for Brooks Brothers.

I don’t remember how the conversation began, but it turned to research when he learned that I was a professor of public health at Columbia University studying climate change

He told me, in no uncertain terms, that he was a born-and-bred New Yorker who loved the city and had no interest in exploring nature. Given his circumstances – and his air-conditioned apartment – rising carbon dioxide and climate change, he believed, had no relevance to him.

I smiled and, trying not to sound condescending, said, “It doesn’t really matter. In reality, you come into contact with climate change three times a day.”

Surprised, he asked, “What do you mean, three times a day?”

“Simple,” I replied. “Breakfast, lunch, and dinner.”

His eyes widened. “I don’t understand.”

I continued: “You know about carbon dioxide, or CO2. It is the principal greenhouse gas driving global warming, and most people recognize that. What they don’t understand is that rising carbon dioxide can also affect the nutritional quality of the food they eat.”

His response was one word: “How?

I hesitated; I didn’t want to sound too wonky. “Plants, like people, are made of different elements. In total, plants require 17 essential elements. Carbon, hydrogen, and oxygen come from air and water, while the remaining 14 – including vital nutrients such as nitrogen – are absorbed through the roots from the soil. More CO2 can stimulate plant growth because more carbon is available. But that increase in carbon is not accompanied by an equivalent increase in soil nutrients. As a result, the nutritional quality of the foods we eat – from rice and potatoes to wheat and beans – declines. There is less protein and lower concentrations of essential elements such as iron and zinc. Plants become carbon-rich and nutrient-poor.” (1)

At that moment, the car lurched forward and picked up speed. His face remained impassive; I couldn’t tell whether he was impressed or skeptical. But the moment had passed. Silence settled between us, and he left the train at Fulton Street.

I wish I could say that his response to climate change was exceptional. Unfortunately, it is common. People may acknowledge that rising CO2 and climate change will affect nature yet still believe that they will not be personally affected. This is understandable. When you live in a city or suburb, as most of us do, nature can seem abstract and disconnected from daily life.

The way we scientists communicate the dangers of climate change does not help. When I ask my students at Columbia what image comes to mind when they hear the phrase “climate change,” the most common answer is a polar bear stranded on a fragment of ice. The bear looks lost, forlorn, and uncertain – worthy of a sympathetic “Aww.”

Nothing against polar bears, but once the cuteness and concern pass, the image is easy to dismiss. Very few of us will ever encounter a polar bear. The reality is far more immediate: you – every aspect of you – will be affected by rising CO2 and the climate changes it drives.

There are many dimensions to that “you,” but food is fundamental. Food is existence. It is energy, motivation, intelligence, growth, repair, disease prevention, and social and cultural identity. Apocalyptic biblical and Hollywood scenarios aside, food is emerging as one of the most direct pathways through which rising CO2 and climate change threaten human life. (2)

Food security has many definitions, but at its core are three pillars: availability, meaning that food is physically present and affordable; nutrition, meaning that it supplies the elements necessary for health; and safety, meaning that it is free from dangerous contamination.

Rising CO2 and climate change affect all three – profoundly.

The first pillar, availability, is evident to almost anyone who follows the news. The media gravitates toward disasters – floods, droughts, fires – because people pay attention. Agricultural catastrophes figure prominently among these images, and climate change increasingly plays a role in them.

The United States is renowned as a global breadbasket. At the heart of that breadbasket is Kansas, the nation’s leading producer of winter wheat – our daily bread. By increasing the frequency and severity of extreme events, including drought, climate change is undermining our ability to produce those amber waves of grain. At the end of August 2026, half of Kansas was experiencing drought, while another 25 percent was classified as abnormally dry. (3) As climate change intensifies, agricultural production becomes more volatile, marked by sharper highs and lows. This climatic whiplash is becoming endemic. Combined with escalating civil and regional conflicts, it is making an already serious problem – food availability – even worse. (4)

Food must be available, but it must also provide what the body needs. Numerous empirical studies and research syntheses, known as meta-analyses, confirm that rising CO2 can diminish nutritional quality. The consequences are especially significant for wheat and rice, staple crops that together provide food for roughly 35 percent of the world’s population. In poorer countries that depend heavily on these staples, the effects on nutrition and hidden hunger are particularly severe. (5) But the threat is likely ubiquitous, reaching even the Wall Street broker on the A train.

Finally, there is safety. If you are reading this, raise your hand if you have ever experienced food poisoning. (All right, you can put it down.) Every kind of food can serve as a breeding ground or vehicle for pathogens: viruses such as norovirus, bacteria such as Salmonella, and fungi that produce toxins such as aflatoxins. These contaminants can enter the human body with explosive consequences and, occasionally, cause death.

These hazards have one important characteristic in common: they are sensitive to temperature. The warmer the environment, the faster Salmonella can multiply. Fresh water, essential for growing and washing produce, becomes even more critical, while the use of contaminated water – a greater risk during drought – can have grave consequences. Abrupt climate shifts will increasingly affect food safety. Cyclospora is no joke. (6)

There is more. Billions of people eat rice every day, and most rice is grown in flooded paddies. Warmer temperatures and elevated carbon dioxide can alter soil bacteria and biogeochemistry in these systems, potentially producing pronounced increases in inorganic arsenic and raising cancer risks across the Global South. (7)

Our food system is global and extraordinarily complex. Rising CO2 and climate change will affect every pillar of food security, often in ways we still do not fully understand. Then there is the joker in the deck: the possibility of a super El Nino, which, if the past is prologue, could disrupt food production, nutrition, and safety worldwide.

One might assume that communicating the urgent need to confront these threats would be a national priority. One would be wrong. USAID, the USDA, and the Food Safety and Inspection Service have all seen their budgets slashed. The National Institute of Food and Agriculture, a cornerstone program that funds agricultural research at land-grant universities, faces further cuts. The result will be less knowledge, weaker protections, and higher food prices.

The science of food security and the threats it reveals are still emerging, but they demand immediate attention. Failing to respond will result, quite literally, in illness and death – potentially for millions of people.

When it comes to climate science, scientists as a group may not be especially skilled at reaching nonscientists. I need to think more like an advertiser: to foreground the empirical evidence showing what rising CO2 and climate change are doing to the food system, and to explain the science simply and persuasively. The message must be unmistakable: you will be affected. Politics has forced science out of the ivory tower; now we have to enter the trenches. One-on-one conversations on subway trains are a start, but I can do more. Food is the obvious place to begin. I need to speak, write, and communicate in ways that make the danger immediate, change the narrative, and bring the “you” into focus. Doing so amid the minefield of social media will be difficult, and time is short. But the public – and, one hopes, policymakers – need to understand what is at stake. Now.

Forget the polar bears for a moment. The climate crisis is already on your plate.

Lewis H. Ziska is an American plant physiologist, academic, and author. He is an associate professor in Environmental Health Sciences at the Mailman School of Public Health at Columbia University.

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References

https://magazine.publichealth.jhu.edu/2024/less-nutritious-crops-another-result-rising-co2

Mirzabaev, A., Kerr, R.B., Hasegawa, T., Pradhan, P., Wreford, A., von der Pahlen, M.C.T. and Gurney-Smith, H., 2023. Severe climate change risks to food security and nutrition. Climate Risk Management, 39, p.100473.

https://www.plantmaps.com/en/us/state/kansas/current-drought-conditions

https://salatainstitute.harvard.edu/what-war-and-climate-change-mean-for-staple-food-prices/

Zhu, C., Kobayashi, K., Loladze, I., Zhu, J., Jiang, Q., Xu, X., Liu, G., Seneweera, S., Ebi, K.L., Drewnowski, A. and Fukagawa, N.K., 2018. Carbon dioxide (CO2) levels this century will alter the protein, micronutrients, and vitamin content of rice grains with potential health consequences for the poorest rice-dependent countries. Science advances, 4(5), p.eaaq1012.

https://www.cdc.gov/dpdx/cyclosporiasis/index.html

Wang, D., Kim, B. F., Nachman, K. E., Chiger, A. A., Herbstman, J., Loladze, I., … & Ziska, L. H. (2025). Impact of climate change on arsenic concentrations in paddy rice and the associated dietary health risks in Asia: an experimental and modelling study. The Lancet Planetary Health, 9(5), e397-e409.

Changes in yield (bushels per acre) of winter wheat in Kansas. Data are from the National Agricultural Statistical Service. Note the increasing variation in yield with climate uncertainty.