United Press International: U.S. scientists say they’ve determined earthworms can change the chemical nature of the carbon in North American forest litter and soils. Purdue University scientists, along with researchers from the Smithsonian Institution and Johns Hopkins University, studied the effect of earthworms on forest chemistry by comparing carbon composition in forests that vary in earthworm activity. They found forests with greater numbers of invasive earthworms tend to have litter and soil organic …