Revised 24 May 2019

The carrying capacity of an environment is the maximum population of a species that can be supported in that environment. Both Individual organisms and ecosystems have developmental stages where there is initially a period of slow growth and a period of rapid growth followed by a stable period of non-growth where there is a steady state climax. This also applies to the growth of the population of an organism within an ecosystem as shown in Figure 12. 

Figure 12: Carrying capacity

The limiting factor that prevents further population growth is the availability of nutrients. In climax ecosystems there are complex food webs where the cycles of nutrients are tightly interlinked. The carrying capacity of each organism in a given environment is limited by the stock of any indispensable necessity of life that is in shortest supply. The following simplified diagram shows the interdependence of the nutrient cycles.

Figure 13: Interdependence of Nutrient cycles. (Ehrlich et al., 1977, p77)

Herbivores feed on plants, and carnivores feed on herbivores and fellow carnivores. As can be seen, the ultimate limiting factor of total biomass (combined carrying capacities of all organisms) in an ecosystem is the process of photosynthesis carried out by plants, algae, and certain bacteria.