[LUM#9] What if plants no longer fed us?
“Eat five fruits and vegetables a day.” A slogan that could well become outdated in the coming years. Why? Because rising CO2 levels in the atmosphere are degrading the nutritional quality of plants. A phenomenon that is still poorly understood and which researchers at the Montpellier Laboratory of Plant Biochemistry and Molecular Physiology.
“In 50 years, the rise in CO2 levels—which we can no longer control—will likely significantly boost agricultural production, but these crops will be of lower nutritional quality.” This is the alarming assessment shared by Alain Gojon, a researcher at the Laboratory of Plant Biochemistry and Molecular Physiology.
A global food challenge
And yet, it had all started out so well. For once, the rise in atmospheric CO2 levels caused by human activity—which is responsible, among other things, for global warming—had a positive effect. It stimulated the growth of countless plant species by boosting their photosynthesis. “ Photosynthesis,” explains Alain Gojon, “is the ability of plants to produce sugars using CO2, light, and water . It is the foundation of the food chain of life.”
As early as the 1990s, researchers saw this as offering a twofold promise: boosting global food production while capturing excess CO2. “It’s one of the possible solutions to the food challenge facing the planet, ” adds Alain Gojon. “There will be 9 billion of us by 2050, and more than 10 billion before the end of the century. We’re going to have to feed everyone.” Initial calculations based on projected increases in CO2 levels estimate a 40% rise in agricultural production . A windfall.
Fewer minerals but more sugar
More than 2,600 experiments have been conducted to test this prediction. These experiments, known as FACE ( Free-Air CO₂ Enrichment), involve creating an artificial CO₂ bubble over field crops using a system of nozzles that continuously inject carbon dioxide. Hundreds of plant species, including wheat, tomatoes, rice, potatoes, and beans, have been tested around the world. “The first publications appeared as early as 1998, but it is only in the last three or four years that we have had summaries of all these experiments.” The result: two conclusions.
First, the increase in agricultural productivity, which turned out to be much smaller than researchers had hoped.“We’re closer to 10% than 40%,” explains Alain Gojon. The second, unexpected finding is the significant loss of minerals and proteins in these plants grown under CO2: “The loss of nitrogen, which is a major component of proteins, is about 15%. For minerals such as phosphorus, potassium, calcium, magnesium, or iron, the loss is around 10%.”
Recent studies on rice varieties even report a loss of vitamins of up to 40%. On the other hand, there is more sugar since the carbon content is increased.
Serious health consequences
Within fifty years, common food crops could therefore be higher in energy but lower in essential nutrients, with potentially serious consequences for the human population.
“A recent study indicates that, globally, an additional 120 million people will suffer from protein deficiency, and an additional 1.5 billion women and children will suffer from severe anemia due to iron deficiency.” Once again,it is the Global South that will pay the highest price. “ In the North, ” the researcher continues, “nutritional imbalance could lead to an increase in obesity and overweight conditions due to the rising sugar content in plants.” To better understand this phenomenon, the QualiSud laboratory will analyze changes in the nutritional quality of foods produced under high CO2 levels to assess their impact on human health.
This process may already be underway, as researchers have found that when comparing modern wild plants with samples from herbariums dating back to the pre-industrial era, the mineral content of the same species is already lower. “ The problem,” continues Alain Gojon, “is that nothing in our current understanding of the physiology of mineral nutrition in plants allows us to explain this.” And this is precisely the focus of the research set to begin in Montpellier in January 2019.
Two hypotheses
“The first hypothesis is that, for reasons we do not yet understand, rising CO2 levels affect how plants function, making them less efficient at absorbing minerals from the soil. ” The second hypothesis, which the Eco&Sol laboratory in Montpellier will investigate in collaboration with Alain Gojon’s team , is that “CO2 could affect the functioning of the biogeochemical cycles of elements in the soil. The idea is that plants may still be functioning just as well, but there are fewer mineral elements available to them in the soil.”
By testing these hypotheses, the researchers hope, of course, to understand this mechanism, but perhaps also to find solutions to this future crisis. “Thanks to the unique facilities available atthe Ecotron in Montpellier, we will use 140 plant lines to try to identify the genetic factors responsible for the negative impact of high CO2 levels on plant nutritional quality.”
With the hope, perhaps, of producing plant varieties less affected by rising CO2 levels.
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