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How does competition cause population growth to level off near carrying capacity?

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Common wildebeest — population ecology A herd of common wildebeest (*Connochaetes taurinus*) migrating across a dusty savanna in Africa. The animal is a keystone species (i.e., a species with a disproportionately large effect on its biological community) in plains and acacia savanna ecosystems from southeastern Africa to central Kenya.

In population ecology, competition acts as a density-dependent factor that regulates population size. As a population grows, the number of individuals per unit area increases, leading to heightened competition for essential resources such as food, water, and nesting sites.1

When resources become limited, this increased competition forces the population's exponential growth rate to slow down. As the population size approaches the environment's carrying capacity—the maximum population density an environment can sustain—the growth rate diminishes nearly to zero.23

This process is described by logistic population growth, which produces an S-shaped logistic curve. In this model, the availability of resources and the intensity of competition effectively constrain the population, preventing it from exceeding the environment's capacity to support it. If the population exceeds this threshold, resource shortages typically cause the population size to decrease until it stabilizes.234