Rising CO2 Boosts Calories, Lowers Nutrients in Food

Anyone eating what now constitutes a healthy meal of rice and tomatoes may not get enough essential nutrients in the future. Increased CO₂ in the air is reducing the nutritional quality of crops: they contain less zinc, iron and proteins, for example. These nutrients are decreasing by 4.4% on average, but some are decreasing by 38%. At the same time, the number of calories is increasing, which can contribute to obesity. Concentrations of harmful substances such as mercury and lead may also be increasing, although more data are needed to investigate this

Wake-up call

Globally, many people depend on rice or wheat for their nutrition. Both crops show a marked decrease in essential nutrients as CO₂ levels increase. A decline in nutritional value can significantly affect people's health - even if enough food is available - and can contribute to malnutrition. Environmental scientist Sterre ter Haar sees her study as a wake-up call. 'With food security, we often think of whether people can fill their stomachs. Our research emphasises that food security also means nutrient security. We need to pay more attention to that.'

Comparing data from different studies

The researchers analysed and compared crop data from different studies. In these studies, researchers grew crops at various CO₂ levels. Although plenty of data were available, the different CO₂ concentrations used made the studies difficult to compare. However, the Leiden researchers discovered that the effect on the plants' growth of the CO₂ levels they studied was linear: if the CO₂ level doubles, so too does the effect on the nutrients. This allowed the researchers to make a baseline measurement that allowed them to compare the data. They looked at 43 crops in total, including rice, potatoes, tomatoes and wheat.

How realistic is this scenario?

The crops for the different studies were grown under experimental conditions both indoors and out. How realistic is it that our food will become more calorific, less nutritious and more toxic? 'The CO₂ level for the baseline measurement was at 350 parts per million (ppm) and we looked at what would happen at 550 ppm, a level we expect to reach in our lifetimes,' said researcher Sterre ter Haar. 'We currently live at 425 ppm, so we're already halfway through this model.' According to the researchers, the results suggest that our diet is already less nutritious than a few decades ago. We may have to adjust our diet in the future.

More research needed

The Leiden researchers hope this study will inspire further research on the effect of CO₂ on not only other crops, but also on whether climate change affects our food otherwise and how we can adapt crops to climate change. Can we grow them in a different way in greenhouses, for example? 'Luckily, there's lots of innovation in the Dutch food sector and we have strong research institutions that can study this,' says Ter Haar. 'We really can make headway together.'