One-sixth of the planet's cropland has toxic levels of one or more metals

Mining is the main anthropogenic cause of heavy metal soil contamination. The image shows an aerial view of the Aznalcóllar mine, photographed in 2017. The first 30 centimeters of soil are the foundation of life. This foot-deep slice of the pedosphere is the vital space for most plant roots. When roots go deeper, it’s to anchor the plant, not to nourish it. Within this narrow band, bacteria, fungi, nematodes, and countless other microscopic organisms form the so-called biological crust, which in turn supports the larger life forms above. Now, a review of thousands of studies — and many more soil samples — reveals that this same 30-centimeter layer also contains toxic concentrations of metals in agricultural soil used to grow the food humans eat. The massive study, published Thursday in Science, estimates that up to 17% of farmland worldwide contains excessive levels of one or more metals and metalloids. A team of researchers from the U.S., Europe, and China reviewed thousands of exis ... Read full article.