Carrying Capacity
Because of limiting factors, each ecosystem has a finite capacity for growth connected to its carrying capacity.
•Carrying capacity is the maximum number of individuals an environment can support over time without degradation. It depends on resources, habitat quality and interactions between species. Populations may temporarily exceed carrying capacity but will eventually decline as competition intensifies and resources become depleted.
•Carrying capacity: The size of the population that can be supported indefinitely on the available resources and services of that ecosystem.
When a population is BELOW its carrying capacity, it will INCREASE in size. Birth rate exceeds death rates.
When a population is ABOVE its carrying capacity, it will DECREASE in size. Death rate exceeds birth rates.
Carrying capacity is dynamic – it can alter as a result of changes in either abiotic or biotic factors. The carrying capacity can also be lowered (reduced K) by resource destruction and degradation during an overshoot period. Example : Drought
Water becomes the limiting factor for kangaroos. Therefore the carrying capacity of the population is decreased, because the number of individuals that the current environment can support has been decreased.
Biotic changes that alter carrying capacity
•Biotic interactions can raise or lower carrying capacity.
•Increased competition for food reduces the number of individuals that can survive.
•For example, if grazing animals remove too much vegetation, plant biomass declines, reducing the long-term carrying capacity for herbivores.
Abiotic changes that alter carrying capacity
•Abiotic factors such as rainfall, temperature and soil quality influence resource availability.
•During drought water becomes limiting and carrying capacity falls.
•Extreme heat may reduce plant productivity which lowers herbivore numbers.
•Sudden storms may destroy nesting sites and alter population structure.
•Fire removes vegetation, but may create conditions for pioneer species to flourish.
•Floods may sweep away soil or deposit nutrients.
•The long-term effect depends on how fast the habitat recovers and whether species can adapt to new conditions.