Earthworms by far constitute the greatest biomass of animals in soil. In organically farmed grass fields, up to 1000 earthworms per m2 can be found, with a biomass of several hundred grams per m2. Earthworms are important for bioturbation in the soil, and without earthworms we would not have mull soil. Earthworms are often used in ecotoxicological studies of various environmental toxins and pesticides. We use earthworms as model animals in studies on climatic stress, especially cold and drought stress.
