CO₂ & Food: Less Nutrition, More Calories – A Growing Threat

Rising carbon dioxide levels are increasing the caloric content of food crops but simultaneously decreasing their nutritional value and potentially increasing toxicity, according to a new study.

Nutrient Decline Linked to Increased CO2

Researchers at Leiden University in the Netherlands developed a method to compare multiple studies on plant responses to elevated CO₂ levels. The results indicated that while crop yields increase, the density of essential nutrients declines. Specifically, levels of zinc were found to drop, while levels of lead increased.

“Seeing how dramatic some of the nutritional changes were, and how this differed across plants, was a big surprise,” said Sterre ter Haar, a lecturer at Leiden University. “We aren’t seeing a simple dilution effect but rather a complete shift in the composition of our foods … This also raises the question of whether we should adjust our diets in some way, or how we grow or produce our food.”

Establishing a Baseline for Comparison

Scientists have been studying the effects of increased CO₂ on plants for approximately a decade, but comparing results has been challenging. The new research established a baseline measurement based on the linear relationship between CO₂ levels and nutrient impact – a doubling of CO₂ corresponds to a doubling of the effect on nutrients.

This allowed researchers to analyze nearly 60,000 measurements across 32 nutrients and 43 crops, including staples like rice, potatoes, tomatoes, and wheat. Previous studies, while providing valuable data, often had small sample sizes and were difficult to compare due to the continuously increasing baseline CO₂ levels in the atmosphere.

The study used a baseline gas concentration of 350 parts per million – considered by some to be the last “safe” level – and compared it to a projected concentration of 550 parts per million, which some scientists anticipate reaching by 2065. On average, most nutrients are expected to decrease by 3.2% with the rise in concentration.

Significant Nutrient Drops Predicted

The research predicts a substantial decline in zinc levels in chickpeas, potentially as high as 37.5%. Significant decreases in protein, zinc, and iron are also expected in essential crops such as rice and wheat. Researchers warn of potential “devastating health consequences,” including “hidden hunger,” where individuals consume sufficient calories but lack adequate nutrients.

The current CO₂ level is 425.2 parts per million, and the paper notes that this level has already resulted in “lowered levels of plant nutrition due to CO₂ rise.”

Global Implications and Further Research

The Netherlands, a major agricultural exporter with three-quarters of its production destined for export and over 4,100 hectares of greenhouses utilizing CO₂-enriched environments to boost yields, is particularly relevant to these findings.

“Climate change isn’t a faraway problem,” said Ter Haar. “The effects are already on our dinner plate.”

Courtney Leisner, an assistant professor at Virginia Tech, welcomed the study, calling it a valuable foundation for further investigation. “This study offers critical insights into how environmental conditions affect crop nutritional quality, which is essential for sustaining future food security,” she said.

Jan Verhagen, a researcher at Wageningen University, noted that factors such as fertilizer application also play a significant role in crop nutrition, and that the relationship between CO₂ and nutrient levels may not be solely causal. He emphasized the need for further experiments to inform breeding programs for nutrient-rich crops under varying environmental conditions.

Ter Haar acknowledged that the meta-analysis raises more questions than it answers and expressed a desire to continue studying the interplay between climate change and nutrient content. “Our goal isn’t to scare people,” she said. “The first step in solving a problem is acknowledging it, and with that, we think our study could be a useful puzzle piece.”

The research was published in the journal Global Change Biology.