Carrying capacity
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In ecology, the carrying capacity of an environment for a particular species is a measure of the steady-state density that the species can have for a particular habitat to support sustainably.
Species adopt one of two adaptive strategies :
- Strategy r-selected : the species has a high reproduction rate, but is very sensitive to environmental factors, in particular predation. Therefore, the populations do exceed the carrying capacity. This strategy is typical of insects.
- Strategy K-selected : the species has a low reproduction rate and usually a long life span. They are submitted to low predation rate and population may grow over the carrying capacity. Environmental stress usually lead to hormonal disrupting to prevent ovulation, or to abortions. This strategy is typical of mammals.
When populations exceed the carrying capacity, famine and disease tend to reduce the size of the population.
The belief that "Humans are the only species known to possess the ability to increase their carrying capacity" does not make sense. To begin with, the Earth's capacity to carry humans is the issue, not what putative ability humans have to carry anything. Humans have no ability to increase the Earth's carrying capacity of our species. But they can maximise it by making prudent and sustainable use of every available resource, and they can indeed increase it in the short term by plundering the Earth's capital resources, thus reducing it in the medium and long term.
An alternative definition for carrying capacity is: the maximum population of a particular species a particular region can support without hindering future generations' ability to maintain the same population. An area of land is said to have the carrying capacity. The capacity will differ for different species.
See also Ecological yield, Sexual selection, Overpopulation.