densitydependent

Densitydependent, or density-dependent, describes processes whose effects scale with the density of a population. In ecology, such factors regulate population size because encounters among individuals increase or resource availability decreases as density rises. Consequently, birth rates may fall and/or death rates may rise at higher densities, producing self-limiting growth patterns.

Mechanisms of density dependence include competition for limited resources like food and space, which reduces juvenile survival and adult fecundity; increased contact rates that elevate disease transmission and parasitism; intensified territoriality or social stress; and higher predation risk when prey are more detectable or aggregations attract predators. The strength and timing of density dependence can vary with species, life stage, season, and habitat quality. It can affect production in one or both components of population growth: births and deaths.

Density-dependent processes are contrasted with density-independent factors, such as weather events or natural disasters, that affect populations regardless of density. In epidemiology and population biology, distinguishing density-dependent from density-independent effects helps explain patterns of resilience, oscillations, or crashes. Some models, like the logistic growth model, formalize density dependence with carrying capacity, K, constraining growth as N approaches K.

Implications of density dependence are central to conservation, resource management, and Understanding population viability. Variations in density dependence influence carrying capacity, recovery potential after declines, and the response of populations to environmental change.