Near boat launches, worms had dramatically changed the soil. At 200 feet away from one launch site, the soil has a litter layer, made up of leaves and other dead plant material, about six inches thick. But at about 30 feet from the boat area, that organic layer disappeared. Yoo says that he and his team could blindfold themselves further out from a site, and, as they walked toward the boat landing, be able to feel the soil beneath their feet change when they stepped on earthworm habitat. Organic matter is springy and soft, but the areas the worms had transformed felt more solid underfoot. This sort of change takes around five to 10 years of worm burrowing, adds Yoo.