Overshoot (ecology)

In population dynamics and population ecology, overshoot occurs when a population temporarily exceeds the long term carrying capacity of its environment. The environment usually has mechanisms in place to prevent overshoot. For example, plants are only able to regenerate and regrow a few times after being consumed before completely dying off. The consequence of overshoot is called a collapse, a crash or a die-off in which there is a decline in population density. The entire sequence or trajectory undergone by the population and its environment together is often termed 'overshoot-and-collapse'.

Overshoot can occur due to lag effects. Reproduction rates may remain high relative to the death rate. Entire ecosystems may be severely affected and sometimes reduced to less-complex states due to prolonged overshoot. The eradication of disease can trigger overshoot when a population suddenly exceeds the land's carrying capacity. An example of this occurred on the Horn of Africa when smallpox was eliminated. A region that had supported around 1 million pastoralists for centuries was suddenly expected to support 14 million people. The result was overgrazing, which led to soil erosion.

An attempt to apply this concept to human experience is Overshoot: The Ecological Basis of Revolutionary Change, by William R. Catton, Jr., which updates the 1974 book,The Limits to Growth. The Club of Rome study The Limits to Growth used a computer model which was based on overshoot and collapse. The Limits to Growth simulation showed in several scenarios how overshoot could happen based on an assumption of hard limits to resources, but did not deal with questions of substitution of limited resources with renewable resources.

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