Since that time there has been considerable reconciliation, which has partly fl owed from mere practical common sense. People have begun to notice how much, in practice, the two causes converge. Animals and the organisms around them always need each other. The whole environment cannot be served except through its parts, and animals form an essential part of every ecosystem. The huge majority of animals still live in the wild, where their chance of surviving at all depends on the plants, bacteria, rivers, etc. around them. (Only a few species, such as rats and herring gulls, can do well by exploiting resources provided by humans.) Equally, plants and rivers commonly need many of their accustomed animals. Obvious examples are pollinating insects and birds, beavers to maintain swamps, scavengers to recycle waste, and insectivorous creatures, from anteaters to frogs, to keep insect populations from overeating the vegetation. The bad effects of removing such animals have been repeatedly seen. Even with captive animals, too, large-scale ill-treatment inevitably does have bad environmental effects. It is not just an accident that factory farming produces appalling pollution. It is bound to do so, because proper treatment of waste would cost too much to allow the cheapness which is its main aim.