For decades, scientists have noticed a disturbing trend in much of the produce we eat. Over time, the nutritional value of produce has been decreasing. There are fewer vitamins and minerals in the fruits and vegetables we eat. Much of this trend has been explained by soil depletion; modern farming methods are stripping soil of nutrients.

However, soil depletion isn’t the only variable changing the nutritional quality of produce; scientists have discovered that the rising CO2 levels associated with climate change are going to have a large impact.

On one hand, higher levels of CO2 are likely to have a positive impact on the quantity of crops produced. Plants will find it easier to extract CO2 from the air to make carbohydrates. Scientists also believe that less water will be needed for crops grown in a high CO2 environment.

But it’s not all good news.

For this latest study, researchers compared crops grown in normal and enriched CO2 environments over the course of six growth years in Japan, Australia and the United States. Though the current CO2 levels are 400 parts per million, studied crops were grown at the 546 – 586 parts per million level expected within four to six decades. The impact of these levels was examined on wheat, rice, peas, soybeans, corn and sorghum.

With the exception of corn and sorghum, significant drops in zinc, iron and protein were found. The largest of these drops was a 9.3% decrease in the zinc and iron levels in wheat. With certainty, scientists were able to conclude that crops are losing nutrients as CO2 levels go up.

What’s the big deal?

According to researchers, some two billion people live in countries where more than 60 percent of their zinc and iron come from crops likely to be impacted by rising CO2 levels. Already in 2014, deficiencies of these nutrients cause an annual loss of 63 million life years. With nutrient levels dropping in crops due to CO2, that number is likely to increase.

While much of the focus around climate change has been on drought, increasing temperatures and rising sea levels, the impact of CO2 on crops is not to be ignored.