Viable population

Minimum viable population (MVP) is a lower bound on the population of a species, such that it can survive in the wild. This term is used in the fields of biology, ecology, and conservation biology. More specifically, MVP is the smallest possible size at which a biological population can exist without facing extinction from natural disasters or demographic, environmental, or genetic . The term "population" rarely refers to an entire species. For example, the undomesticated dromedary camel is extinct in its natural wild habitat; but there is a domestic population in captivity and an additional feral population in Australia. Two groups of house cats in separate houses which are not allowed outdoors are also technically distinct populations. Typically, however, MVP is used to refer solely to a wild population, such as the red wolf.

Minimum viable population is usually estimated as the population size necessary to ensure between 90 and 95 percent probability of survival between 100 and 1,000 years into the future. The MVP can be estimated using computer simulations for population viability analyses (PVA). PVA models populations using demographic and environmental information to project future population dynamics. The probability assigned to a PVA is arrived at after repeating the environmental simulation thousands of times.

For example, for a theoretical simulation of a population of 50 giant pandas in which the simulated population goes completely extinct, 30 out of 100 stochastic simulations projected 100 years into the future are not viable. Causes of extinction in the simulation may include inbreeding depression, natural disaster, or climate change. Extinction occurring in 30 out of 100 runs would give a survival probability of 70%. In contrast, in the same simulation with a starting population of 60 pandas, the panda population may only become extinct in four of the hundred runs, resulting in a survival probability of 96%. In this case the minimum viable population that satisfies the 90- to 95% probability for survival is between 50 and 60 pandas. (These figures have been invented for the purpose of this example.)

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