Ecological balance is a theory stipulating that natural conditions, including numbers of various animal and plant species, remain stable on their own through variations over time. The theory, also known as balance of nature, also holds that natural equilibrium can be changed significantly by new species entering an ecosystem, the disappearance of some species, man-made changes to the environment or natural disasters.
Examples of disturbances to ecological balance include bombing during the Vietnam War that destroyed habitat for many species. As part of modern global commerce, trees and vegetation are sometimes removed, and those areas in which vegetation is removed and pavement is added tend to expand. As a result, water balance changes, and species of animals and plants must move or change to find alternative habitats and sources of food.
The theory of ecological balance holds that natural systems typically correct themselves when small changes occur. For instance, if a particular species becomes too plentiful, numbers of a predator species may also increase temporarily to bring total numbers back into balance. Most ecologists no longer subscribe to the theory of ecological balance and instead feel that natural systems are best described by catastrophe theory, which holds that small changes in one component of a natural system can result in significant and permanent changes to the entire system.