Limiting Factor (Populations) — Definition & Examples

Limiting Factors (Ecology)

These are factors present in the environment of a given species which could limit growth, abundance, or distribution of a population in that particular environment.

Density-Dependent Limiting Factors

A lot of these factors are called density-dependent because they are dependent on the size of the population. The larger the population the more limiting factors will come into play. For example, one limiting factor is competition for resources. There are only so many nutrients, water, and light available for a group of plants, and therefore there is a limit to the number of plants which can grow in that area. This can be exasperated by non-native species that use the same resources but have no natural predators.

Density-Independent Limiting Factors

Limiting factors can also be density-independent. These include things like natural disasters. A population can decrease rapidly due to a hurricane or wildfire.

An important thing to realize about limiting factors is that a population can only grow as much as the least limiting factor allows. This is known as Liebig’s Law of the Minimum. In other words, if you have a plant and give it a lot of sunlight but not a lot of water, the plant will struggle to grow because it doesn't have enough water.

What Is a Limiting Factor?

Imagine that you are making gift bags for a party. You have 50 gift bags. You want to fill each bag with one chocolate, one lollipop, and one sticker each. You have 50 stickers, 50 lollipops, but only 25 chocolates. You can't make that many bags if they each need their own chocolate.

In this case, the chocolate was a limiting factor. You can see the same thing occurring in ecological systems. If you have 50 deer and they each need one acre of grass, one gallon of water, and one tree for shelter each, then having less than needed of any of those things is going to limit the deer population.

These kinds of limiting factors are density-dependent. If you only had 25 gift bags to fill, the chocolate would not be a limiting factor. It is dependent on the size of the population if it's a limiting factor or not.

A density-independent limiting factor is something that could happen no matter the size of the population. A forest fire due to a lightning strike could happen whether there are 50 deer or 500 deer. The fire could kill the deer and limit the population, making it a density-independent limiting factor.

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Density-dependent limiting factors are things like competition for resources, predator and prey relationships, parasitism, and disease. Competition happens when a population becomes too large and must compete for food, water, shelter, and other resources. Basically, these limiting factors only happen when a population becomes too big and its environment can no longer support it.

Density-independent factors include things like fires and other natural disasters, odd weather, and clear-cutting forests. So, in other words, these factors are random occurrences that cause the size of a population to decline.

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A limiting factor can be abiotic, like the amount of water, nutrients, or land that is available.

A limiting factor can also be biotic. A predator or parasites can be a limiting factor for a population of prey. Limiting factors are very important to keep populations from destroying an environment.

If a single factor wasn't available to stop population growth, a population would continue expanding until it has consumed all resources.