The history of the pesticide DDT offers a large number of stories that all illustrate the ripple effect. For example, in 1965 villages in Bolivia were sprayed with DDT to eliminate the mosquito that carries malaria. Within a week or two, most of the villagers' cats had died, apparently from licking DDT residue off their fur or paws. In the absence of the cats, rodents invaded peoples' homes, and they experienced an outbreak of hemorrhagic fever, which was carried by the rodents.
DDT was used in the 1950s and 60s to control a variety of insects. However DDT does not break down quickly in the environment, instead entering the food chain. There it undergoes biomagnification, accumulating in the bodies of the creatures who consume it, and then in the bodies of the creatures who consume those creatures, and so on. DDT has an estrogen-like activity in the body of warm-blooded creatures, and its presence in the bodies of birds of prey caused them to lay thin-shelled eggs, which did not survive incubation. Many species of birds in the US, including the bald eagle, are still recovering from DDT-induced population drops.