Carbon dioxide (CO2) in the atmosphere continues to rise -- likely impacting the food we eat -- as numerous recent studies show that important crops and most plant species may become less nutritious.
CO2 levels have increased steadily since the industrial revolution of the 19th century, rising from 280 parts per million (ppm) to current levels over 400 ppm, which is the highest CO2 concentration in human history -- a threshold which had not been reached in millions of years.
The US Global Change Research Program (USGCRP) projects CO2 levels to reach between 540 ppm and 958 ppm by 2100.
While elevated CO2 boosts plants’ productivity by stimulating photosynthesis and causing plants to grow larger, it also increases the carbohydrates content and the ratio of carbohydrates to nutrients in plants.
Nutrients do not increase at the same rate as carbohydrates; therefore, plants end up having relatively lower concentrations of proteins and minerals in comparison to carbohydrates, according to Mathematical Biologist Irakli Loladze.
"For every bit of food you eat, there will be more carbs, less protein, less minerals -- zinc, iron, calcium, magnesium, potassium, and so on," Loladze said.
Loladze was one of the first scientists to sound the alarm on the subject.
Loladze first made this predication while doing his post-doctoral work at Princeton University in 2002.
However, the process to compile the data necessary to prove his hypothesis was very slow. It took ten years to compile enough data and two years to publish the analysis of the data, Loladze said.
In 2014, his analysis unequivocally showed that nutrients drop and carbohydrates go up as CO2 increases.
By 2016, the United States was the first country to formally acknowledge that rising CO2 lowers the concentrations minerals and proteins in important crops and most plant species, according to Loladze.
It was a key finding in the 2016 U.S. report on climate change impacts on human health. It was one of the only few key findings that are high confidence due to the overwhelming amount of data.
Adequate food quantity is a well-known requirement for global food security, but the importance of food quality is often overlooked, a USGCRP report reads.
In developed nations with abundant food supplies, like the United States, the prevalence of malnutrition may not be intuitive and is often under-appreciated, according to the USGCRP.
Developed nations like the United States also have the resources to supplement foods with nutrients, such as adding vitamin D to milk.
However, in the U.S., it is estimated that between 38 and 45 percent of the population’s diets fall below the estimated average requirements for calcium and magnesium, according to the USGCRP.
Meanwhile, many developing nations do not have the resources to fortify their food supply with necessary nutrients to combat the declining number of nutrients in crops. This puts human nutrition at high risk.
Many nutritionists often dismiss the link between rising CO2 and malnutrition, either because they have never heard of it or they will say it’s only small drop. Many nutritionists will point out that we can always fortify our food but the fortification of food is limited in extent and scope, Loladze said.
"It’s like saying, we can combat global warming by just turning up air conditioning in our rooms. It’s a local approach to trying to solve a global problem," Loladze said.
There have been numerous studies to monitor the impact of elevated CO2 levels on nutrient levels in crops.
A Harvard study published online on Aug. 2 found that if CO2 levels continue to rise as projected, the populations of 18 countries may lose more than 5 percent of their dietary protein by 2050 due to a decline in the nutritional value of rice, wheat and other staple crops.
Study authors estimate that roughly an additional 150 million people may be placed at risk of protein deficiency. This was the first study to quantify the risk of elevated CO2.
An University of Gothenburg study published in April 2017 concluded that higher CO2 levels have significant negative effects on the nutritional value of wheat grains.
“Based on our results, we cannot yet make accurate predictions about effects on human health since people eat a lot of other things in addition to wheat-based products,” study author Malin Broberg said.
There are numerous factors playing into how lower plant nutrition will impact human nutrition globally. There is also high uncertainty on how rising CO2 levels will influence plant nutrition.
There will also be other environmental changes, such as increasing temperatures and shifting precipitation patterns, that will play a role on the impacts, said Broberg.
“Considering that developments in agricultural practices and crop breeding are likely to happen, it is difficult to say how these factors will interact and what the resulting effect on crop quality will be," Broberg said.
USGCRP currently projects that the overall nutrient value of crops will continue to fall as CO2 levels continue to increase over the next century.