Our CO2 emissions are causing wheat to have poorer baking quality.

The bread we eat 25 years from now could be both more difficult to bake with and harder for some of us to tolerate. Rising CO₂ levels in the atmosphere are changing the composition of proteins in wheat. This is shown by a new study led by the Leibniz Institute for Food Systems Biology at the Technical University of Munich (TUM), published in the journal Food Chemistry. In the study, the researchers grew ten varieties of winter wheat in a field near Rheinbach, Germany. The wheat was grown conventionally using nitrogen fertilizer; organically grown wheat was not included in the experiment. Half of the crop grew under normal conditions, while the other half was exposed to additional CO₂, bringing the average daytime concentration to 546 ppm. This is roughly the level expected around the middle of the century. The protein in a wheat kernel consists of gluten and a range of other proteins, including amylase/trypsin inhibitors (ATIs). After harvesting, the researchers measured the content of these proteins in the kernels and found that the wheat from the CO₂-enriched field contained 4.7 percent less protein than the wheat from the control field. At the same time, the ATI content increased by 5.7 percent. ATIs are a group of proteins that can trigger wheat allergies and non-celiac wheat sensitivity. According to the study, they may also worsen other pre-existing diseases. Nine of the ten varieties had higher ATI levels under elevated CO₂. However, it has not been established whether the increase in ATIs is large enough to affect our health. Bread rises less effectively The gluten content was also negatively affected. Gluten is not a single protein but an entire family of proteins that can be divided into two main groups: Gliadins, which make dough stretchy. These come in several types. Glutenins, which make dough elastic and strong. They are divided into small and large subunits. The researchers examined 21 gluten proteins, and 15 of them declined significantly when the wheat was exposed to increased CO₂. Overall, the total amount of the 21 measured gluten proteins fell by 18.7 percent. “Our results also showed that the lower concentration of gluten proteins was associated with poorer baking quality,” says Sabrina Geisslitz, a researcher at the Leibniz Institute who led the study, in a press release. In the experiment, the volume of the bread fell by 4.1 percent. Sabrina Geisslitz explains that the changes vary considerably depending on the wheat variety. The researchers also measured the content of the parts of gluten proteins that can trigger a reaction in people with celiac disease when gluten is broken down in the intestine. These generally declined under elevated CO₂. In some varieties, however, their content increased. Should not focus solely on high yields According to the researchers, the results underscore how important it is to identify and breed varieties that retain good baking quality as CO₂ levels rise while also containing as few potentially problematic proteins as possible, rather than breeding solely for high yields. This is far from the first study to show that our crops lose important nutritional content as atmospheric CO₂ levels rise. In 2011, researchers also found that although additional CO₂ often increases wheat yields, protein content declines—and that this happens even when yields do not increase. Other crops besides wheat also lose important nutrients. In 2014, researchers reported in the journal Nature that wheat, rice, peas and soybeans contain less zinc and iron when grown under elevated CO₂. According to the researchers, this could threaten the nutrition of the many people around the world who obtain most of their zinc and iron from precisely these crops. Four years later, a study showed that nutrients such as protein, iron and zinc decline in rice as CO₂ levels increase. A Nordic research project in which plants are grown in the Technical University of Denmark’s climate chambers, simulating a warmer climate, has also shown that barley is negatively affected. Although the additional CO₂ acts as a growth stimulant, the negative effects of the heat are greater. The concentration of CO₂ in the atmosphere has risen sharply from approximately 340 ppm in 1980 to approximately 425 ppm in 2024, and according to projections, it is not unlikely to reach close to 600 ppm by 2050. Even today, CO₂ levels are the highest they have been in at least two million years. The last time they were this high, the global temperature was 1–2.5 degrees higher than it is now, and sea levels were 5–25 metres higher, indicating the direction in which the world is heading. Our CO₂ emissions are so extensive that they have caused the atmospheric concentration of the greenhouse gas to rise at least 100 times faster than during the natural CO₂ increases of the past 800,000 years. Natural emissions in the past were caused by factors including the Earth’s rotation, plate tectonics, massive decomposition of vegetation and volcanic activity.