Research indicates that the effect of large grazer droppings on groundwater is zero, compared to a variety of other sources of pollution. In natural grazing, the density of animals is much lower than in livestock. In dune areas, the risk caused by human fecal matter from recreationists was found to be greater than that of any other animal. Because natural grazing leans on the self-reliance of the animals, grazers are generally not medicated. In contrast, farm animals are regularly treated preventively with medication that's difficult to break down, and continue its way into the environment.