The term limit is associated with the word control; hence, limiting factor refers to the factor that controls the growth or size of the population. In other words, it slows down or decreases the rate of population growth.

Density-dependent means the population growth varies with the population density. The limiting factors, which are mentioned, only control the population growth if the density reaches a particular level. For example, when a population density in a forest reaches its maximum level, it becomes quite crowded. This often results in competition for resources and diseases. In other words, this is nature’s way of controlling the population when it reaches its maximum capacity. In this process, both biotic and abiotic factors are involved.

A density-independent limiting factor will affect a population without taking into consideration the current population size in a certain area. Whether the population size has reached its carrying capacity or not, a density-independent limiting factor will always affect the population.

An example of this limiting factor is a wildfire. Whether the forest has a low population or a high population of animals, a wildfire can still cause the death of most life-forms living in the forest. The occurrence of a wildfire is not dependent on whether the animal population has reached the carrying capacity of such forest or not.

Human activities, such as the invasion of natural environment or habitat of other species, can lead to species extinction. Most of the time, humans invade the forest and compete with animals for resources, particularly food and space. As a result, the habitats of animals become smaller. In turn, when the area gets smaller, the carrying capacity decreases too. If an area has an extremely low carrying capacity, the population could be wiped out; hence, an extinction would occur.

Excessive levels of phosphorus and nitrogen in a freshwater environment cause the carrying capacity of algae to increase and the carrying capacity of fishes to decrease. When a high concentration of nutrients in the water are present, the population of algae explodes, This causes a thick, green muck that affects the clear water and it reduces the ability of fishes to find food and obtain oxygen. This results in hypoxia and the death of many fishes.

Organisms that feed on fishes would become affected too. The ecosystem that surrounds the freshwater environment would experience a decrease in its carrying capacity because it could no longer support the needs of the organisms for clear water and food.

In a rainforest biome, water is not really a limiting factor. Unlike in desert and tundra biomes, this biome does not have harsh climate conditions because there is an ample supply of rainfall during the entire year. In addition, photosynthesis only requires a small amount of water.