Rising Emissions Are Lowering Plants’ Nutritional Value

After one of the hottest summers ever recorded, greenhouse gas emissions should be a “hot” topic. The period from June through August 2026 tied for the warmest summer on record globally. Greenhouse gases trap heat in the atmosphere, warming the planet and driving climate change.e.

Carbon dioxide (CO₂) is the primary greenhouse gas emitted through human activities, and atmospheric CO₂ concentrations have risen by more than 50% since pre-industrial times. But the effects of rising CO₂ extend beyond a warmer world — they may also be changing the food we grow.

Higher CO₂ levels can increase the growth and yields of many plants. But here, bigger does not necessarily mean better. Research shows that elevated CO₂ can also reduce concentrations of important nutrients in many food crops, including protein, iron and zinc. In other words, rising CO₂ isn’t only changing our climate; it may also be changing the nutritional quality of the food on our plates.

Read on to “grow” your knowledge about how rising CO₂ affects plants — and why reducing emissions matters for both the planet and our health.

Photosynthesis and the CO₂ Fertilization Effect

Some atmospheric CO₂ is necessary for plant life. Plants use CO₂, along with sunlight and water, during photosynthesis, producing glucose and releasing oxygen. Plants use that glucose as a source of energy to support growth and other cellular processes.

At first glance, elevated CO₂ can appear beneficial because it can increase plant growth, a phenomenon known as the CO₂ fertilization effect. Many important food crops, including wheat, rice and soybeans, use a photosynthetic pathway known as C3 photosynthesis. Higher atmospheric CO₂ can stimulate photosynthesis and increase biomass production in these plants.

However, other environmental conditions such as rising temperatures could weaken the CO₂ fertilization effect. A study modeled the seed yields of wheat, rice, soybean, and maize during projected mid- and late- century increases in CO₂ and temperature. While the results were crop specific, exposure to elevated CO₂ generally increased seed yield, supporting the CO₂ fertilization effect. Adding elevated temperature revealed that these yield increases are likely to be diminished or completely eliminated in maize, rice, and wheat.

Quality Over Quantity

But regardless of how other climate-related changes may affect the CO₂ fertilization effect, elevated atmospheric CO₂ can reduce concentrations of important nutrients in many food crops.

Multiple hypotheses have been proposed to explain the relationship between rising CO₂ levels and declining nutrient concentrations, but no single cause has emerged. Notably, the effects vary by nutrient, species and plant family, and some nutrients, such as potassium, may increase. Nonetheless, researchers have documented declines in important nutrients in certain crops, including global staples such as rice and wheat.

Elevated CO₂ can decrease plants’ nitrogen concentrations, which can translate into lower protein content because nitrogen is an essential component of proteins. A 2025 meta-analysis found declines in nitrogen concentrations in rice and wheat grown under elevated CO₂.

Micronutrients like zinc and iron can also decrease. The same meta-analysis found an average 7.1% decrease in zinc in C3 plants under elevated CO₂ levels that scientists expect we will reach during our lifetimes. Chickpeas experienced a 37.5% decrease in zinc, while iron and zinc concentrations in rice and wheat also declined.

Elevated CO₂ can also alter the balance of nutrients within plants. Increased photosynthesis can lead to greater carbohydrate production, even as concentrations of protein and certain micronutrients decline. As a result, some crops may provide less protein and fewer micronutrients relative to their carbohydrate content.

What This Means

Declining nutrient concentrations in staple crops could worsen malnutrition, particularly hidden hunger — when people consume enough calories but do not get enough essential vitamins and minerals. For populations already at risk of nutrient deficiencies, declines in protein and micronutrient concentrations could make it even more difficult to meet nutritional needs.

Protein helps build and repair tissues throughout the body. Protein deficiency can contribute to muscle loss, impaired immune function and other health problems.

Micronutrients play critical roles in our health, too. For example, zinc helps our immune system function properly, wounds heal, and bones grow, meaning that a zinc deficiency can weaken the immune system, slow wound healing, and impede children’s growth. Iron helps support our energy levels, and therefore low iron levels can cause fatigue, lower brain health, and weaken the immune system.

Populations already at high risk of nutrient deficiencies could be disproportionately affected by changes in crop nutrition. In regions where diets rely heavily on staple crops such as wheat and rice, including parts of South Asia and Sub-Saharan Africa, declining nutrient concentrations could exacerbate existing deficiencies and increase the number of people at risk.

PULLQUOTE: [The impact of rising CO₂ on food nutrient levels could exacerbate health inequities globally … In countries with the least diverse and least quality diets, this will further deepen the gap.] – [ Saskia de Pee, Chief Analytics & Science for Food & Nutrition at the World Food Programme]

Seeds of Hope

The 2025 meta-analysis on the impact of rising CO₂ levels on plant nutrition modeled the effects of various CO₂ emissions pathways on the nutritional value of plants and concluded: “the lower the CO₂ emissions, the lower the nutrient loss.”

Rising CO₂ isn’t only changing our climate — it may also be changing the nutritional quality of the food we depend on. Reducing greenhouse gas emissions is therefore not only a climate imperative; it is increasingly important to protecting our food systems and human health.

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