When is carrying capacity reached

For populations which grow exponentially, growth starts out slowly, enters a rapid growth phase and then levels off when the carrying capacity for that species has been reached. The size of the population then fluctuates slightly above or below the carrying capacity.

Reproductive lag time may cause the population to overshoot the carrying capacity temporarily. Reproductive lag time is the time required for the birth rate to decline and the death rate to increase in response to resource limits. In this scenario, the population will suffer a crash or dieback to a lower level near the carrying capacity unless a large number of individuals can emigrate to an area with more favorable conditions.

An area's carrying capacity is not static. The carrying capacity may be lowered by resource destruction and degradation during an overshoot period or extended through technological and social changes.

An example of dieback occurred in Ireland after a fungus infection destroyed the potato crop in During this potato famine approximately 1 million people died and 3 million people emigrated to other countries.

Increased food production due to improved agricultural practices, control of many diseases by modern medicine and the use of energy to make historically uninhabitable areas of Earth inhabitable are examples of things which can extend carrying capacity. The question is how long will we be able to keep increasing our population on a planet with finite size and resources?

Population Impact Homo sapiens is a species possessing a diversity of individual needs. Thus, sub-populations will have different requirements and different impacts on the environment. For example million vegetarians will have a significantly different environmental impact than million meat-eaters.

This can be demonstrated by comparing the affect on water supplies by both sub-populations. About tons of water are needed to produce 1 ton of grain. Add to this the amount of water that goes into the production of meat, and you can see that meat comsumption places more stress on global water supplies than grain consumption. Although it is difficult to determine the exact human carrying capacity for a country as large and diverse as the U.

Studies on human history, though, provide evidence that the concept in which the human population size reaches the maximum level is relatively not that common. Most of the time, the population density of humans adjusts, especially as the actual food production fluctuates for that area or region. The picture below shows an example of a carrying capacity graph Figure 1.

Here, the carrying capacity symbol: K for a biological species is marked by the red dotted horizontal line to describe the number of organisms that the environment can support sustainably for a given time.

Notice that it coincides with the stable equilibrium , which refers to the population size that has reached a steady-state as it aligns with the carrying capacity. The growth is depicted as S-shaped a characteristic of a logistic growth. The S-shape logistic growth forms when the growth rate is slow at first lag phase and next speeds up exponential phase. Then, the rate slows down again as the population size reaches carrying capacity.

In the real world, though, population size tends to rise and dip in oscillations from the carrying capacity rather than a flat line as depicted in the graph. To calculate for the carrying capacity K , the equation for the change of population size can be used for deriving a formula for K Ref. A sample worksheet of carrying capacity and population biology can be found here.

A population may grow at a faster rate and follow a J-shaped curve. When the birth rate surpasses the death rate of the species, this results in exponential growth.

However, this trend soon changes as resources become limited. The growth rate slows down. Soon, it reaches a stable equilibrium where biomass in the given area seems unchanged over a certain period of time. At this point, the death rate appears to be compensated by the birth rate within a population. This means the per capita birth rate equals the per capita death rate. By contrast, when deaths appear to outgrow births, this indicates that the carrying capacity has been exceeded.

This is a case of overshoot. The population may go below the carrying capacity. This can occur, for instance, during disease and parasitic outbreaks. Several factors affect the carrying capacity of an ecosystem. These factors include food supply, water supply, habitat space, competition intraspecific and interspecific , physical factors e. The sum of these factors that end up restricting the biotic potential of a species is referred to as environmental resistance.

In nature, the population of a given area may reach carrying capacity when the maximum population size is reached for a given area with limited resources.

Because water, food, and space abound, the turtles can thrive and reproduce at an exponential rate. However, as the population grows, competition is intensified as well. Turtles compete for food, water, and space. Male turtles compete with other males for mates.

These factors will limit the biotic potential of the turtles. When the population seems stable, e. Another example is the tree population in a forest. This means that the trees can grow without fiercely competing for sunlight, nutrients, and space. This also implicates that the new sprouts may not be able to thrive in the same manner because the tall and older trees will cast a shadow over them, making sunlight hard to access from down below.

Humans create sub-populations with different needs according to lifestyle. For example, some of them follow an omnivorous diet whereas others are strictly vegan. Because of this, the demand for food resources may vary.

Humans have also found ways to solve and curb competition on resources, such as space, food, and water through technology. For example, agriculture and husbandry helped expand the food supply. Humans learned to plant crops and breed animals to meet demands for food. They also learned eventually to build a safe shelter away from predators.

However, certain modern technology and anthropogenic activities cause critical damage to the population of other species.