The Process of Ecological Saturation

Defining Ecological Saturation

• Ecological saturation is a bit of a fuzzy term and could more precisely be termed habitat saturation. Habitat saturation is what happens when an expanding population has used up whichever resource is most limiting, like space, food or water. In a system that is closed ̵1; nothing can get in or out, like an island ̵1; this means that the population has hit its limits and can̵7;t grow anymore. In an open system, this might be the point where individuals start dispersing, or moving on to other habitats.

Population Growth

• Imagine that you drop four of an imaginary animal, the "lork," on an island that has lots of habitat and no predators. Those lorks will reproduce unchecked as long as there is enough food and space for everybody. This stage is known as exponential growth, because the population doubles every generation and grows really fast. As the population gets bigger, there are fewer resources for everybody and they are harder to find. At this point, population growth will start to slow down.

Carrying Capacity

• Once the island habitat in our example is holding all of the lorks it can hold, it has reached carrying capacity or the point where the habitat is saturated. Carrying capacity is determined by the habitat component that is in the least supply, since that is the resource that runs out first. A saturated habitat cannot support more individuals, and reaching this point means other ecological principles come into play.

What Happens When You Reach Saturation?

• Our imaginary island is now completely saturated with lorks, so now what? The lorks will be competing with each other for scarce resources, so they might set up rigid territories and defend them aggressively. There might not be enough food, so they might not have the energy to reproduce or might even starve. Everyone might be so crowded that a disease can spread easily between the lorks and reduce the population. Over time, the lorks might specialize so that they don̵7;t compete with each other as much or they might not grow as big or they might find another way to adapt. If we suddenly had a bridge to the island, the young lorks would probably take off in search of greener pastures. Organisms in the real world live in more complex systems than our island, but many of the principles we discussed here can be seen in nature every day.