The condition of equilibrium among the components of a natural community such that their relative numbers remain fairly constant and their ecosystem is stable. Gradual readjustments to the composition of a balanced community take place continually in response to natural ecological succession and to alterations in climatic and other influences. By removing or introducing plants or animals, by polluting the environment, by destroying habitats and by rapidly increasing their own numbers, humans can cause major changes, some of which may be irreversible.