Demographic stochasticity Demographic stochasticity is often only a driving force toward extinction in populations with fewer than 50 individuals. Random events influence the fecundity and survival of individuals in a population, and in larger populations these events tend to be stabilized toward a steady growth rate. However, in small populations there is much more variance, which can in turn cause extinction.[1] Environmental stochasticity Small, random changes in the abiotic and biotic components of the ecosystem that a population inhabits fall under environmental stochasticity.