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Overpopulation occurs when a species' population exceeds the carrying capacity of its environment.[citation needed] It can result from an increase in births (fertility rate), a decline in the mortality rate, an increase in immigration, or a depletion of resources. When overpopulation occurs the available resources become too limited for the entire population to survive.

Animal overpopulation

In the wild, overpopulation often causes growth in the populations of predators. This has the effect of controlling the prey population and ensuring its evolution in favor of genetic characteristics that render it less vulnerable to predation (and the predator may co-evolve, in response).[1]

In the absence of predators, species are bound by the resources they can find in their environment, but this does not necessarily control overpopulation, at least in the short term. An abundant supply of resources can produce a population boom followed by a population crash. Rodents such as lemmings and voles have such cycles of rapid population growth and subsequent decrease.[citation needed] Snowshoe hares populations similarly cycled dramatically, as did those of one of their predators, the lynx.[2]

The introduction of a foreign species has often caused ecological disturbance, such as when deer and trout were introduced into Argentina[3] or when rabbits were introduced to Australia and when predators were introduced in turn to attempt to control the rabbits.[4]

Some species such as locusts experience large natural cyclic variations, experienced by farmers as plagues.[5]

Human overpopulation

Overpopulation can result from an increase in births, a decline in mortality rates against the background of high fertility rates.[6][7] It is possible for very sparsely populated areas to be overpopulated if the area has a meagre or non-existent capability to sustain life (e.g. a desert). Advocates of population moderation cite issues like quality of life and risk of starvation and disease as a basis to argue against continuing high human population growth and for population decline.


References

  1. ^ Scott, Joe. "Predators and their prey - why we need them both"<

    Overpopulation occurs when a species' population exceeds the carrying capacity of its environment.[citation needed] It can result from an increase in births (fertility rate), a decline in the mortality rate, an increase in immigration, or a depletion of resources. When overpopulation occurs the available resources become too limited for the entire population to survive.

    Animal overpopulation

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