The carrying capacity or support of a biological species in an environment is the maximum population size that the environment can support indefinitely in a given period, taking into account the food, water, habitat, and other necessary elements available in that environment. In population biology, carrying capacity is defined as the maximum load of the environment,[1] which is different from the concept of population equilibrium. That of humans on Earth is dependent on the technological infrastructure available among other factors.
For the human population, more complex variables such as medical care and sanitation are sometimes considered. As population density increases, the birth rate often decreases and the death rate usually increases. The difference between the birth rate and the death rate is natural growth. The carrying capacity could support a positive natural increase, or it could require a negative natural increase. Therefore, carrying capacity is the number of individuals that an environment can support without significant negative effects to the given organism and its environment. Below carrying capacity populations typically increase, while above carrying capacity they typically decrease. A factor that keeps the population size in balance is known as a regulating factor or limiting factor. Population size declines above carrying capacity due to a number of factors depending on the species in question, these may include abiotic factors such as lack of space, food supply or sunlight; or biotic factors, such as intraspecific competition and interspecific competition.
The origins of the term carrying capacity are uncertain; some researchers indicate that it was used "in the context of international shipping"[2] or that it was first used during laboratory experiments with microorganisms in the 20th century.[3] A recent review found the first use of the term in an 1845 report by the US Secretary of State to the Senate.[4].
Examples
One of the best-studied predator-prey relationships in the world is that of the moose and wolf populations of Isle Royale National Park[5] in Lake Superior. Without the wolves, the elk would destroy the island's vegetation.[6] Without the elk, the wolves would die. The first scientists who studied the subject thought that there would come a time when the increasing population of wolves would lead them to kill all the moose calves and then starve to death. This has not happened since inbreeding,[6] diseases and environmental factors[7] have limited the wolf population naturally.
Load capacity factor
Introduction
The carrying capacity or support of a biological species in an environment is the maximum population size that the environment can support indefinitely in a given period, taking into account the food, water, habitat, and other necessary elements available in that environment. In population biology, carrying capacity is defined as the maximum load of the environment,[1] which is different from the concept of population equilibrium. That of humans on Earth is dependent on the technological infrastructure available among other factors.
For the human population, more complex variables such as medical care and sanitation are sometimes considered. As population density increases, the birth rate often decreases and the death rate usually increases. The difference between the birth rate and the death rate is natural growth. The carrying capacity could support a positive natural increase, or it could require a negative natural increase. Therefore, carrying capacity is the number of individuals that an environment can support without significant negative effects to the given organism and its environment. Below carrying capacity populations typically increase, while above carrying capacity they typically decrease. A factor that keeps the population size in balance is known as a regulating factor or limiting factor. Population size declines above carrying capacity due to a number of factors depending on the species in question, these may include abiotic factors such as lack of space, food supply or sunlight; or biotic factors, such as intraspecific competition and interspecific competition.
The origins of the term carrying capacity are uncertain; some researchers indicate that it was used "in the context of international shipping"[2] or that it was first used during laboratory experiments with microorganisms in the 20th century.[3] A recent review found the first use of the term in an 1845 report by the US Secretary of State to the Senate.[4].
Examples
One of the best-studied predator-prey relationships in the world is that of the moose and wolf populations of Isle Royale National Park[5] in Lake Superior. Without the wolves, the elk would destroy the island's vegetation.[6] Without the elk, the wolves would die. The first scientists who studied the subject thought that there would come a time when the increasing population of wolves would lead them to kill all the moose calves and then starve to death. This has not happened since inbreeding,[6] diseases and environmental factors[7] have limited the wolf population naturally.
Easter Island has been cited as an example of a precipitous drop in human population. When just under 100 people first arrived on the island, it was covered with trees and a wide variety of foods. In 1722, the island was visited by Jacob Roggeveen, who estimated a population of 2,000 to 3,000 inhabitants with very few trees, a rich soil, a good climate" and where "the whole county was cultivated." Half a century later, it was described as "a poor land" and "largely uncultivated." The ecological collapse that followed has been attributed variously to overpopulation, slave traders, European diseases (including a smallpox epidemic that killed so many and so quickly that the dead were left unburied and a tuberculosis epidemic that wiped out a quarter of the population), social unrest, and invasive species (such as Polynesian rats that may have wiped out ground-based bird nests and palm seeds) Whatever the combination of factors, only 111 inhabitants remained on the island in 1877. For whatever reasons (whether the Moai cult, survival, status, or ignorance), the question of How many humans the island could actually support seems to have never been answered.
Another example is the island of Tarawa,[8] where the limitation of space is evident, especially because new landfills cannot be excavated to dispose of solid waste, due to limitations in the subsoil rock and the lack of topographic elevations. With colonial influence and an abundance of food (relative to life before 1850), the population has grown to such an extent that we can speak of overpopulation.[9].
Mathematical model
The Lotka-Volterra equation is a simple mathematical model of population dynamics that shows how in a closed system, like that of wolves and moose on Isle Royale, prey reduction will cause the predator population to decline rapidly. An expanded example can be used for cases of multiple species competing for the same resources or one species feeding on multiple prey.
Limiting factors
Of all the nutrients essential for the growth of a population, there is always one that tends to be depleted and is called limiting factor. Sometimes this factor may not be a nutrient, but rather a changing physical factor such as temperature. For ecologists, knowing what the limiting factors are is of utmost importance because in this way they can predict, to the extent possible, the consequences of the changes produced in ecosystems.[10].
Exponential growth
When an area is in good condition for the growth and development of a population, it is said that its growth is exponential until the resources that make this possible are exhausted. It is then when the population will experience the effects of a high mortality rate, which in turn is the result of the competition that occurs between the animals that make up this population due to the scarcity of resources.[10].
This type of growth occurs in some species of insects and small organisms as well as in plants.
Humans
Contenido
La aplicación de la capacidad de carga para la población humana ha sido criticada por no tener en cuenta correctamente los procesos a múltiples niveles entre los seres humanos y el medio ambiente, que tienen una naturaleza fluida y de no-equilibrio, y que a menudo se usan en el contexto de culpabilización de la víctima.[11].
Los partidarios de la idea argumentan que los seres humanos, al igual que todas las especies, tienen una capacidad de carga limitada. El tamaño de la población, los niveles de vida y agotamiento de los recursos varían, pero el concepto de capacidad de carga sigue siendo válida. La capacidad de carga de la tierra ha sido estudiada por modelos de simulación por ordenador como World3.
Technology
Technology is an important factor in the dynamics of carrying capacity. For example, the Neolithic revolution increased the carrying capacity of the world in relation to humans through the invention of agriculture. Today, the use of fossil fuels has artificially increased the world's carrying capacity by using stored sunlight, although this has resulted in pollution of the oceans, excessive predation of forest areas such as indiscriminate logging and burning, as well as misuse of resources. That is to say, there is no sustainable balance since the same human being has been responsible for destroying and polluting the environment irresponsibly. For centuries it was believed that natural resources were infinite, and that they would never be exhausted, today we know that the opposite is true. Other technological advances that have increased the carrying capacity of the world in relation to humans include: polders, fertilizers, compost, greenhouses, land reclamation and fish farming.
The capacity for agriculture on Earth expanded in the last quarter of the century. But there are many predictions about a continued decline in global agricultural capacity (and therefore carrying capacity) that began in the 1990s. Notable is the forecast that China's food production will decline by 37% in the last half of the century, putting the entire world's carrying capacity under strain, as China's population could rise to around 1.5 billion people by 2050.[12] This reduction in China's agricultural capacity (as in other regions of the world) is partly due to the global water crisis, especially due to the extraction of groundwater beyond the limit of sustainability, as has been happening in China since the middle of the century.[13].
ecological footprint
One way to estimate human demand compared to the carrying capacity of the ecosystem is the ecological footprint. Rather than speculating about future possibilities and the limitations imposed by carrying capacity constraints, the ecological footprint provides empirical, non-speculative assessments about the past. It historically compares regeneration rates (biocapacity) in relation to historical human demand (ecological footprint) in the same year.[14][15] One of the results shows that humanity's demand for the year 1999 exceeded the planet's biocapacity by more than 20 percent.[14].
References
[1] ↑ Hui, C. (2006) Carrying capacity, population equilibrium, and envrionment's maximal load. Ecological Modelling, 192, 317-320. http://dx.doi.org/10.1016/j.ecolmodel.2005.07.001.: https://dx.doi.org/10.1016/j.ecolmodel.2005.07.001
[3] ↑ Zimmerer, K.S., "Human Geography and the "New Ecology": The Prospect of Promise and Integration", Annals of the Assoc. of American Geo., 84(1), 108-125, (1994).: http://dusk.geo.orst.edu/prosem/PDFs/human_geog.pdf
[11] ↑ Cliggett, L., "Carrying Capacity's New Guise: Folk Models for Public Debate and Longitudinal Study of Environmental Change", Africa Today, 48(1), 2-19, (2001).
[12] ↑ Economy, E., China vs. Earth, The Nation, May 7, 2007 issue.
[13] ↑ Nielsen, R., The Little Green Handbook, Picador, (2006) ISBN 0-312-42581-3.
[14] ↑ a b Wackernagel, M., Schulz, N.B., et al, “Tracking the ecological overshoot of the human economy,” Proc. Natl. Acad. Sci. USA, 99(14), 9266-9271, (2002).
[15] ↑ Rees, W.E. and Wackernagel, M., Ecological Footprints and Appropriated Carrying Capacity: Measuring the Natural Capital Requirements of the Human Economy, Jansson, A., Folke, C., Hammer, M. and Costanza R. (ed.), Island Press,(1994) http://www.pnas.org/content/99/14/9266.short.: http://www.pnas.org/content/99/14/9266.short
Easter Island has been cited as an example of a precipitous drop in human population. When just under 100 people first arrived on the island, it was covered with trees and a wide variety of foods. In 1722, the island was visited by Jacob Roggeveen, who estimated a population of 2,000 to 3,000 inhabitants with very few trees, a rich soil, a good climate" and where "the whole county was cultivated." Half a century later, it was described as "a poor land" and "largely uncultivated." The ecological collapse that followed has been attributed variously to overpopulation, slave traders, European diseases (including a smallpox epidemic that killed so many and so quickly that the dead were left unburied and a tuberculosis epidemic that wiped out a quarter of the population), social unrest, and invasive species (such as Polynesian rats that may have wiped out ground-based bird nests and palm seeds) Whatever the combination of factors, only 111 inhabitants remained on the island in 1877. For whatever reasons (whether the Moai cult, survival, status, or ignorance), the question of How many humans the island could actually support seems to have never been answered.
Another example is the island of Tarawa,[8] where the limitation of space is evident, especially because new landfills cannot be excavated to dispose of solid waste, due to limitations in the subsoil rock and the lack of topographic elevations. With colonial influence and an abundance of food (relative to life before 1850), the population has grown to such an extent that we can speak of overpopulation.[9].
Mathematical model
The Lotka-Volterra equation is a simple mathematical model of population dynamics that shows how in a closed system, like that of wolves and moose on Isle Royale, prey reduction will cause the predator population to decline rapidly. An expanded example can be used for cases of multiple species competing for the same resources or one species feeding on multiple prey.
Limiting factors
Of all the nutrients essential for the growth of a population, there is always one that tends to be depleted and is called limiting factor. Sometimes this factor may not be a nutrient, but rather a changing physical factor such as temperature. For ecologists, knowing what the limiting factors are is of utmost importance because in this way they can predict, to the extent possible, the consequences of the changes produced in ecosystems.[10].
Exponential growth
When an area is in good condition for the growth and development of a population, it is said that its growth is exponential until the resources that make this possible are exhausted. It is then when the population will experience the effects of a high mortality rate, which in turn is the result of the competition that occurs between the animals that make up this population due to the scarcity of resources.[10].
This type of growth occurs in some species of insects and small organisms as well as in plants.
Humans
Contenido
La aplicación de la capacidad de carga para la población humana ha sido criticada por no tener en cuenta correctamente los procesos a múltiples niveles entre los seres humanos y el medio ambiente, que tienen una naturaleza fluida y de no-equilibrio, y que a menudo se usan en el contexto de culpabilización de la víctima.[11].
Los partidarios de la idea argumentan que los seres humanos, al igual que todas las especies, tienen una capacidad de carga limitada. El tamaño de la población, los niveles de vida y agotamiento de los recursos varían, pero el concepto de capacidad de carga sigue siendo válida. La capacidad de carga de la tierra ha sido estudiada por modelos de simulación por ordenador como World3.
Technology
Technology is an important factor in the dynamics of carrying capacity. For example, the Neolithic revolution increased the carrying capacity of the world in relation to humans through the invention of agriculture. Today, the use of fossil fuels has artificially increased the world's carrying capacity by using stored sunlight, although this has resulted in pollution of the oceans, excessive predation of forest areas such as indiscriminate logging and burning, as well as misuse of resources. That is to say, there is no sustainable balance since the same human being has been responsible for destroying and polluting the environment irresponsibly. For centuries it was believed that natural resources were infinite, and that they would never be exhausted, today we know that the opposite is true. Other technological advances that have increased the carrying capacity of the world in relation to humans include: polders, fertilizers, compost, greenhouses, land reclamation and fish farming.
The capacity for agriculture on Earth expanded in the last quarter of the century. But there are many predictions about a continued decline in global agricultural capacity (and therefore carrying capacity) that began in the 1990s. Notable is the forecast that China's food production will decline by 37% in the last half of the century, putting the entire world's carrying capacity under strain, as China's population could rise to around 1.5 billion people by 2050.[12] This reduction in China's agricultural capacity (as in other regions of the world) is partly due to the global water crisis, especially due to the extraction of groundwater beyond the limit of sustainability, as has been happening in China since the middle of the century.[13].
ecological footprint
One way to estimate human demand compared to the carrying capacity of the ecosystem is the ecological footprint. Rather than speculating about future possibilities and the limitations imposed by carrying capacity constraints, the ecological footprint provides empirical, non-speculative assessments about the past. It historically compares regeneration rates (biocapacity) in relation to historical human demand (ecological footprint) in the same year.[14][15] One of the results shows that humanity's demand for the year 1999 exceeded the planet's biocapacity by more than 20 percent.[14].
References
[1] ↑ Hui, C. (2006) Carrying capacity, population equilibrium, and envrionment's maximal load. Ecological Modelling, 192, 317-320. http://dx.doi.org/10.1016/j.ecolmodel.2005.07.001.: https://dx.doi.org/10.1016/j.ecolmodel.2005.07.001
[3] ↑ Zimmerer, K.S., "Human Geography and the "New Ecology": The Prospect of Promise and Integration", Annals of the Assoc. of American Geo., 84(1), 108-125, (1994).: http://dusk.geo.orst.edu/prosem/PDFs/human_geog.pdf
[11] ↑ Cliggett, L., "Carrying Capacity's New Guise: Folk Models for Public Debate and Longitudinal Study of Environmental Change", Africa Today, 48(1), 2-19, (2001).
[12] ↑ Economy, E., China vs. Earth, The Nation, May 7, 2007 issue.
[13] ↑ Nielsen, R., The Little Green Handbook, Picador, (2006) ISBN 0-312-42581-3.
[14] ↑ a b Wackernagel, M., Schulz, N.B., et al, “Tracking the ecological overshoot of the human economy,” Proc. Natl. Acad. Sci. USA, 99(14), 9266-9271, (2002).
[15] ↑ Rees, W.E. and Wackernagel, M., Ecological Footprints and Appropriated Carrying Capacity: Measuring the Natural Capital Requirements of the Human Economy, Jansson, A., Folke, C., Hammer, M. and Costanza R. (ed.), Island Press,(1994) http://www.pnas.org/content/99/14/9266.short.: http://www.pnas.org/content/99/14/9266.short