Rising CO2 Levels Are Reducing Nutritional Value of Food, Warn Scientists

How Rising CO2 Is Making Our Food Less Nutritious

Climate change’s most insidious effects are often invisible—until now. Scientists warn that our planet’s rapidly increasing CO2 levels are quietly reducing the nutritional value of the plants we rely on for food. While the changes are subtle, researchers say they could already be endangering millions of people with poor diets, with the impact growing worse over the coming decades.

"The diets we eat today have less nutritional density than what our grandparents ate, even if we eat exactly the same thing."

Study Finds Alarming Drop in Key Nutrients

In a study published in Global Change Biology in November, researchers in the Netherlands analyzed the nutrient levels of 43 major crops—including rice, soybeans, and wheat—that represent the bulk of human food sources. Their findings were stark: since the late 1980s, protein, iron, and zinc levels in these crops have declined by an average of 3.2%.

The culprit? A sharp rise in atmospheric carbon dioxide. While the drop may seem small, study lead author Sterre ter Haar warned that even minor reductions could push millions into severe malnutrition. "A quarter of the world’s population is already believed to have anemia," she noted, a condition that impairs the body’s ability to produce oxygen-carrying blood cells.

Why More CO2 Means Less Nutrition

Plants absorb CO2 to fuel their growth, converting it into sugars for energy. At first glance, this might suggest that higher CO2 levels would make crops more abundant. However, the nutrients humans derive from plants—such as minerals like iron and zinc—come from the soil, not the air. As CO2 accelerates plant growth, the concentration of these essential minerals in the crops remains unchanged, effectively diluting their nutritional value.

Lewis Ziska, a plant biologist at Columbia University who has studied this phenomenon for over 20 years, explained the trade-off: "The plant is becoming more efficient, but it’s occurring at a price, from a human perspective."

The Hidden Costs of CO2 Efficiency

The consequences of this nutrient decline are far-reaching. A 2018 study estimated that 175 million additional people could suffer from zinc deficiency due to falling nutrient levels in food. Meanwhile, 1.4 billion women and children could lose 4% of their dietary iron, exacerbating anemia—a condition linked to pregnancy complications, developmental issues, and even death.

The issue is compounded by another effect of high CO2: plants reduce the opening of their microscopic pores, called stomata, to conserve water. While this makes the plants more water-efficient, it also limits their ability to absorb minerals from the soil—minerals that are critical for human health.

What This Means for Global Food Security

Experts emphasize that the nutritional decline is not a future threat but a present reality. With billions already teetering on the edge of malnutrition, even small reductions in nutrient density could have devastating consequences. As CO2 levels continue to rise, the urgency for solutions—whether through agricultural innovation, dietary adjustments, or policy interventions—grows more critical.