Animal modification of native vegetation: Modification of New Zealand's flora by introduced mammals
- Agricultural Field Station, University of California, Davis, California, U.S.A.
An undisturbed environment evolved over a long period and composed only of native plants and animals has a well-established stability that is not delicately balanced. A change in the density of anyone native species of mammal, either by man or some catastrophe, usually does not set off a dramatic chain reaction of responses by the other plant and animal components of the community. Even though the balance of nature is dynamic and not static, a fairly stable plant and animal equilibrium exists where man has not disturbed this environment.
Although natural environments are so stable, man can disrupt the animal-plant relationships by introducing exotic plants or by altering the native vegetation through farming, grazing, logging, or fire. A marked chain reaction of other responses may then be initiated. McNeil (1964) has shown how such man-made modifications of the environment in the state of Michigan resulted in an overpopulation of native white-tailed deer which did great destruction to their own habitat by eating out the native browse in their winter range. Sometimes such modification is irreversible, or nearly so, but often the habitat will eventually recover if the density of ungulates is kept in check.