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Carrying Capacity Definition
The carrying capacity of a biological species in a given habitat, in biology and environmental science, refers to the maximum number of individuals (of that species) that the ecosystem can carry and support, taking into account its geography and physical properties.
What is Carrying Capacity?
In ecology, carrying capacity refers to an environment’s maximum load. The physical characteristics of the surroundings function as restraints (e.g. food, water, competition, etc.). As a result, the population limit is likely to be influenced by these factors. In essence, food availability is a critical element since it influences the size of a species’ population. It does so in such a way that if food demand is not satisfied for a length of time, population size will gradually decline until resources become enough. When food availability surpasses demand, on the other hand, the population will quickly grow and eventually plateau when the source becomes depleted.
The population size at which the population growth rate equals zero is also known as carrying capacity. It should not be confused with the phrase “equilibrium population,” which refers to a population whose gene frequencies have reached a state of balance between mutation and selection pressure.
Carrying capacity refers to the quantity and density of ancient people sustained by a particular location in archaeology. The carrying capacity of an ecosystem is determined by the maximum population during a certain period in this branch of study. However, studies of human history show that the notion of a maximum human population size is extremely uncommon. Human population density varies most of the time, especially as real food production fluctuates for that location or region.
Carrying Capacity Graph
A carrying capacity graph is shown in the image below. The green dotted horizontal line represents the carrying capacity (symbol: K) for a biological species, which describes the number of creatures that the environment can sustainably maintain for a particular time.
It’s worth noting that it’s the same as stable equilibrium, which refers to a population size that has reached a steady-state as it approaches carrying capacity. “Zero-growth” is shown at this point. The growth is shown as an S-shaped curve (a characteristic of logistic growth). When the growth rate is sluggish initially (lag phase) and then accelerates, the S-shape logistic growth emerges (exponential phase). Then, once the population approaches carrying capacity, the pace slows down again.
However, rather than a flat line as represented in the graph, the population tends to rise and dip in oscillations from carrying capacity in the current world.
Carrying Capacity Equation
The equation for the change in population size may be used to derive a formula for the carrying capacity (K):
dN/dt = rN(1-N/K)
The formula for calculating a population change is as follows:
K = rN(1-N)/dN/dt
r denotes the intrinsic rate of growth
N is the population size
dN/dt is the population size change
Carrying Capacity of an Ecosystem
The rate of population growth is constrained by the Earth’s resource availability. A population’s growth rate may be quicker than average, resulting in a J-shaped curve. When the birth rate of a species exceeds its mortality rate, exponential growth occurs. This trend, however, rapidly reverses when resources become scarce. The rate of growth has slowed.
It soon achieves a stable equilibrium, in which the biomass in a particular region seems to remain constant over time. At this stage, the mortality rate within a population appears to be offset by the birth rate. This indicates that the per capita birth and mortality rates are equal.
When deaths appear to outnumber births, however, it implies that the carrying capacity has been reached. It’s an example of an overshoot. It’s possible that the population will go below the carrying capacity. This can happen during illness and parasite epidemics, for example.
The carrying capacity of an ecosystem is influenced by a number of variables. Food supply, water supply, habitat space, intraspecific and interspecific competition, physical variables (e.g. severe heat, drought, etc.), chemical factors (e.g. pH, mineral deficiency, etc.), and anthropogenic influences are all examples of these factors. Environmental resistance refers to the combination of several variables that limit a species’ biotic potential.
Carrying Capacity Examples
i. Turtle Population
When the maximum population size for a specific region with limited resources is achieved, the population of that area may exceed carrying capacity.
For example, a pond with 10 turtles will be sufficient to support the species’ population. The turtles may survive and breed at an exponential rate since there is enough water, food, and room. Competition, on the other hand, becomes more intense as the population rises. Food, water, and space are all in competition for turtles.
Male turtles battle for mates with other males. These variables will restrict the turtles’ biotic potential. When a population appears to be constant, such as 100 turtles, the carrying capacity for that region can be estimated to be 100 turtles.
ii. Forest Population
Another example is a forest’s tree population. Assume that a forest has a carrying capacity of a hundred trees. This means the trees will be able to develop without having to compete for sunshine, nutrients, and space. This implies that the new sprouts may not be able to flourish as well as the older trees, since the taller and older trees will create a shadow over them, making it difficult to reach from below.
Factor Affecting Carrying Capacity
Humans divide the population into sub-populations with distinct demands based on their lifestyle. Some of them, for example, have an omnivorous diet, while others are totally vegan. As a result, the demand for food resources may fluctuate. Humans have also used technology to solve and reduce competition for resources such as space, food, and water.
Agriculture and animal husbandry, for example, contributed to the expansion of the food supply. To meet food demands, humans have learnt to grow crops and raise animals. They ultimately figured out how to construct a secure haven away from predators. Certain contemporary technologies and anthropogenic activities, on the other hand, have a significant negative impact on the population of other species. To develop residences and businesses, some woods and terrestrial ecosystems were destroyed.
During rain and irrigation, pesticides used to fight agricultural pests leach nutrients from the soil. Because of poor garbage disposal, bodies of water have become contaminated.
Many elements in nature restrict population increase. As a result, despite technical advancements that reduce resource rivalry, the human population must contend with additional factors. Sanitation, illnesses, epidemics, and medical treatment are examples of such factors.
The global carrying capacity for humans is predicted to be nine to 10 billion people based on Earth’s demographics and research study statistics. The world’s population is approaching 8 billion people.
The ecological footprint can be utilised as a starting point for research. It is a method of ecological accounting that calculates the human demand on nature. On a global scale, it can assist in determining demand against the planet’s ability to renew. Furthermore, research shows that the Earth has been in an ecological overshoot.
Humans consume more resources and generate trash at a quicker pace than the ecosystem can “heal” or replenish itself. 85 percent of humankind lives in nations with an ecological deficit, meaning their ecological footprint for consumption exceeds their biocapacity.
Carrying Capacity Citations
- Aging Human Populations: Good for Us, Good for the Earth. Trends Ecol Evol . 2018 Nov;33(11):851-862.
- A Quantitative Assessment of Sustainable Development Based on Relative Resource Carrying Capacity in Jiangsu Province of China. Int J Environ Res Public Health . 2018 Dec 9;15(12):2786.
- Carrying Capacity of Spatially Distributed Metapopulations. Trends Ecol Evol . 2021 Feb;36(2):164-173.