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 the population.

Humans are the only species known to possess the ability to increase their carrying capacity.

See also Ecological yield, Sexual selection, Overpopulation.