fjo3 shares a report from the Washington Post: Surging concentrations of carbon in the atmosphere, caused largely by burning fossil fuels, have produced potent changes in the way plants grow -- from increasing their sugar content to depleting essential nutrients like zinc. Experts fear the degradation of Earth's food supply will cause an epidemic of hidden hunger, in which even people who consume enough calories won't get the nutrients they need to thrive. "The diets we eat today have less nutritional density than what our grandparents ate, even if we eat exactly the same thing," said Kristie Ebi, a professor at the University of Washington's Center for Health and the Global Environment.
People in wealthy countries with strong health care systems will have many tools to cope with the change, experts said. But for the world's poorest and most vulnerable, the consequences could be devastating. One study concluded that by the middle of the century the phenomenon could put more than a billion additional women and children at risk of iron-deficiency anemia -- a condition that can cause pregnancy complications, developmental problems and even death. Meanwhile, some 2 billion people across the globe who already suffer from some form of nutrient shortage could see their health problems grow even worse. "The scale of the problem is huge," Ebi said.
Plants depend on carbon dioxide to perform photosynthesis -- but that doesn't mean they grow better when there's more carbon in the air, scientists say. A sweeping survey of changes among 32 compounds in 43 crops found that nearly every plant that humans eat is harmed by rising CO2 levels. [...] For the past several years, [Sterre F. ter Haar, an environmental scientist at Leiden University in the Netherlands and lead author of the survey] and her colleagues have worked to compile a database of all existing research on nutrient changes linked to rising CO2. They tracked down hundreds of studies, ranging from tightly controlled lab experiments to sprawling global analyses of real-world crops.
Next the team used their dataset to calculate the nutritional densities of each crop under different carbon dioxide levels -- and to predict how their composition could continue to shift in the future.
On average, they found, nutrients have already decreased by an average 3.2 percent across all plants since the late 1980s, when the concentration of carbon dioxide in the atmosphere was about 350 parts per million. That figure may seem small, ter Haar said, but with so much of the world already living on the brink of nutrient insufficiency, a drop of just a few percentage points has the potential to push millions of additional people into a health crisis. Researchers are still trying to understand the exact causes of this change. Extra CO2 can make plants grow faster and produce more carbohydrates, but without a matching increase in mineral uptake, nutrients like zinc, iron, and protein become diluted. Higher CO2 also causes plants to open their leaf pores less often, reducing the amount of water -- and dissolved minerals -- they absorb through their roots. At the same time, higher temperatures can further disrupt soil chemistry, affecting how plants take up nutrients and, in some cases, increasing their absorption of harmful substances like arsenic.
Read more of this story at Slashdot.
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