Carrying capacity

Carrying capacity

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The carrying capacity of a biological species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 in an environment
Natural environment
The natural environment encompasses all living and non-living things occurring naturally on Earth or some region thereof. It is an environment that encompasses the interaction of all living species....

 is the maximum population size of the species that the environment can sustain indefinitely, given the food, habitat
Habitat
* Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...

, water
Drinking water
Drinking water or potable water is water pure enough to be consumed or used with low risk of immediate or long term harm. In most developed countries, the water supplied to households, commerce and industry is all of drinking water standard, even though only a very small proportion is actually...

 and other necessities available in the environment. In population biology
Population biology
Population biology is a study of populations of organisms, especially the regulation of population size, life history traits such as clutch size, and extinction...

, carrying capacity is defined as the environment's maximal load, which is different from the concept of population equilibrium.

For the human population, more complex variables such as sanitation
Sanitation
Sanitation is the hygienic means of promoting health through prevention of human contact with the hazards of wastes. Hazards can be either physical, microbiological, biological or chemical agents of disease. Wastes that can cause health problems are human and animal feces, solid wastes, domestic...

 and medical care are sometimes considered as part of the necessary establishment. As population density increases, birth rate
Birth rate
Crude birth rate is the nativity or childbirths per 1,000 people per year . Another word used interchangeably with "birth rate" is "natality". When the crude birth rate is subtracted from the crude death rate, it reveals the rate of natural increase...

 often decreases and death rate typically increases. The difference between the birth rate and the death rate is the "natural increase". The carrying capacity could support a positive natural increase, or could require a negative natural increase. Thus, the carrying capacity is the number of individuals an environment can support without significant negative impacts to the given organism and its environment. Below carrying capacity, populations typically increase, while above, they typically decrease. A factor that keeps population size at equilibrium is known as a regulating factor. Population size decreases above carrying capacity due to a range of factors depending on the species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 concerned, but can include insufficient space, food supply
Food security
Food security refers to the availability of food and one's access to it. A household is considered food-secure when its occupants do not live in hunger or fear of starvation. According to the World Resources Institute, global per capita food production has been increasing substantially for the past...

, or sunlight
Sunlight
Sunlight, in the broad sense, is the total frequency spectrum of electromagnetic radiation given off by the Sun. On Earth, sunlight is filtered through the Earth's atmosphere, and solar radiation is obvious as daylight when the Sun is above the horizon.When the direct solar radiation is not blocked...

. The carrying capacity of an environment may vary for different species and may change over time due to a variety of factors, including: food availability, water supply
Water supply
Water supply is the provision of water by public utilities, commercial organisations, community endeavours or by individuals, usually via a system of pumps and pipes...

, environmental conditions and living space.

The origins of the term carrying capacity are uncertain with researchers variously stating that it was used "in the context of international shipping
Shipping
Shipping has multiple meanings. It can be a physical process of transporting commodities and merchandise goods and cargo, by land, air, and sea. It also can describe the movement of objects by ship.Land or "ground" shipping can be by train or by truck...

" or that it was first used during 19th Century laboratory experiments with micro-organisms. A recent review finds the first use of the term in an 1845 report by the US Secretary of State to the Senate.

Examples


One of the world's best-studied predator-prey relationships is the moose
Moose
The moose or Eurasian elk is the largest extant species in the deer family. Moose are distinguished by the palmate antlers of the males; other members of the family have antlers with a dendritic configuration...

 and wolf population
Population
A population is all the organisms that both belong to the same group or species and live in the same geographical area. The area that is used to define a sexual population is such that inter-breeding is possible between any pair within the area and more probable than cross-breeding with individuals...

 of Isle Royale National Park
Isle Royale National Park
Isle Royale National Park is a U.S. National Park in the state of Michigan. Isle Royale, the largest island in Lake Superior, is over 45 miles in length and 9 miles wide at its widest point. The park is made of Isle Royale itself and approximately 400 smaller islands, along with any submerged...

 http://www.isleroyalewolf.org/ in Lake Superior
Lake Superior
Lake Superior is the largest of the five traditionally-demarcated Great Lakes of North America. It is bounded to the north by the Canadian province of Ontario and the U.S. state of Minnesota, and to the south by the U.S. states of Wisconsin and Michigan. It is the largest freshwater lake in the...

. Without the wolves, the moose would overgraze the island's vegetation. Without the moose, the wolves would die. The first scientists who studied the issue thought that the wolves would eventually overpopulate and kill all the moose calves, then die from famine. This has not occurred as inbreeding, disease and environmental factors have limited the wolf population naturally.

Easter Island
Easter Island
Easter Island is a Polynesian island in the southeastern Pacific Ocean, at the southeasternmost point of the Polynesian triangle. A special territory of Chile that was annexed in 1888, Easter Island is famous for its 887 extant monumental statues, called moai, created by the early Rapanui people...

 has been cited as an example of a human population crash. When fewer than 100 humans first arrived, the island was covered with trees with a large variety of food types. In 1722, the island was visited by Jacob Roggeveen, who estimated a population of 2000 to 3000 inhabitants with very few trees, "a rich soil, good climate" and "all the county was under cultivation". Half a century later, it was described as "a poor land" and "largely uncultivated". The ecological
Ecology
Ecology is the scientific study of the relations that living organisms have with respect to each other and their natural environment. Variables of interest to ecologists include the composition, distribution, amount , number, and changing states of organisms within and among ecosystems...

 collapse which followed has been variously attributed to overpopulation
Overpopulation
Overpopulation is a condition where an organism's numbers exceed the carrying capacity of its habitat. The term often refers to the relationship between the human population and its environment, the Earth...

, slave traders
History of slavery
The history of slavery covers slave systems in historical perspective in which one human being is legally the property of another, can be bought or sold, is not allowed to escape and must work for the owner without any choice involved...

, European diseases (including a smallpox
Smallpox
Smallpox was an infectious disease unique to humans, caused by either of two virus variants, Variola major and Variola minor. The disease is also known by the Latin names Variola or Variola vera, which is a derivative of the Latin varius, meaning "spotted", or varus, meaning "pimple"...

 epidemic
Epidemic
In epidemiology, an epidemic , occurs when new cases of a certain disease, in a given human population, and during a given period, substantially exceed what is expected based on recent experience...

 which killed so many so quickly, the dead were left unburied and a tuberculosis
Tuberculosis
Tuberculosis, MTB, or TB is a common, and in many cases lethal, infectious disease caused by various strains of mycobacteria, usually Mycobacterium tuberculosis. Tuberculosis usually attacks the lungs but can also affect other parts of the body...

 epidemic which wiped out a quarter of the population), social upheaval and invasive species
Invasive species
"Invasive species", or invasive exotics, is a nomenclature term and categorization phrase used for flora and fauna, and for specific restoration-preservation processes in native habitats, with several definitions....

 (such as the Polynesian rat
Polynesian Rat
The Polynesian Rat, or Pacific Rat , known to the Māori as kiore, is the third most widespread species of rat in the world behind the Brown Rat and Black Rat. The Polynesian Rat originates in Southeast Asia but, like its cousins, has become well travelled – infiltrating Fiji and most Polynesian...

s which may have wiped out the ground nesting bird
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...

s and eaten the palm tree seeds). Whatever the combination of factors, only 111 inhabitants were left on the island in 1877. For whatever reasons (whether Moai
Moai
Moai , or mo‘ai, are monolithic human figures carved from rock on the Chilean Polynesian island of Easter Island between the years 1250 and 1500. Nearly half are still at Rano Raraku, the main moai quarry, but hundreds were transported from there and set on stone platforms called ahu around the...

 worship, survival, status or sheer ignorance), the question of how many humans the island could realistically support never seems to have been answered.

The Chincoteague Pony
Chincoteague Pony
The Chincoteague Pony, also known as the Assateague horse, is a breed of pony that developed and lives in a feral condition on Assateague Island in the United States states of Virginia and Maryland. The breed was made famous by the Misty of Chincoteague series written by Marguerite Henry starting...

 Swim http://www.kyhorsepark.com/imh/bw/chinco.html is a human-assisted example.

Both herds are managed differently. The National Park Service owns and manages the Maryland
Maryland
Maryland is a U.S. state located in the Mid Atlantic region of the United States, bordering Virginia, West Virginia, and the District of Columbia to its south and west; Pennsylvania to its north; and Delaware to its east...

 herd while the Chincoteague Volunteer Fire Company
Chincoteague Fire Department
The Chincoteague Fire Department is a historic U.S. building located at 4026/4028 Main Street, Chincoteague Island, Virginia. This building was initially constructed in 1930 and expanded in 1957....

 owns and manages the Virginia herd. The Virginia herd, referred to as the "Chincoteague" ponies, is allowed to graze on Chincoteague National Wildlife Refuge
Chincoteague National Wildlife Refuge
The Chincoteague National Wildlife Refuge is a wildlife preserve operated by the U.S. Fish & Wildlife Service. It is primarily located on the Virginia side of Assateague Island with portions located on the Maryland side of the island as well as Morris Island and Wildcat Marsh...

, through a special use permit issued by the U.S. Fish and Wildlife Service. The size of both herds is restricted to approximately 150 adult animals each in order to protect the other natural resources of the wildlife refuge.


A further example is the Island of Tarawa
Tarawa Atoll
Tarawa is an atoll in the central Pacific Ocean, previously the capital of the former British colony of the Gilbert and Ellice Islands. It is the location of the capital of the Republic of Kiribati, South Tarawa...

, where the finite amount of space is evident, especially since landfills cannot be dug to dispose of solid waste, due to constraints in the subsurface rock and lack of topographic elevations. With colonial influence and an abundance of food (relative to life before the year 1850), the population has expanded to the extent that overpopulation
Overpopulation
Overpopulation is a condition where an organism's numbers exceed the carrying capacity of its habitat. The term often refers to the relationship between the human population and its environment, the Earth...

 is transparently present.

Mathematics


The Lotka-Volterra equation
Lotka-Volterra equation
The Lotka–Volterra equations, also known as the predator–prey equations, are a pair of first-order, non-linear, differential equations frequently used to describe the dynamics of biological systems in which two species interact, one a predator and one its prey...

s are simple mathematical model
Mathematical model
A mathematical model is a description of a system using mathematical concepts and language. The process of developing a mathematical model is termed mathematical modeling. Mathematical models are used not only in the natural sciences and engineering disciplines A mathematical model is a...

 of population dynamics
Population dynamics
Population dynamics is the branch of life sciences that studies short-term and long-term changes in the size and age composition of populations, and the biological and environmental processes influencing those changes...

 which show how in a closed system, like that of the wolves and moose on Isle Royale
Wolves and moose on Isle Royale
Isle Royale, the principal island of Isle Royale National Park in the United States, is home to a predator-prey relationship between wolves and moose that is unlike any other in the world...

, limited prey will cause the predator population to decline rapidly. An extended example can be used where multiple species are competing for the same resources, or single species feed on multiple prey.

Humans


The application of carrying capacity for the human population has been criticized for not successfully capturing the multi-layered processes between humans and the environment, which have a nature of fluidity and non-equilibrium, and that it often has a blame-the-victim
Victim blaming
Victim blaming occurs when the victim of a crime, an accident, or any type of abusive maltreatment are held entirely or partially responsible for the transgressions committed against them. Blaming the victim has traditionally emerged especially in racist and sexist forms...

 framework.

Supporters of the concept argue that humans, like every species, have a finite carrying capacity. Animal population size, living standards, and resource depletion vary, but the concept of carrying capacity still applies. The carrying capacity of Earth has been studied by computer simulation models like World3
World3
The World3 model was a computer simulation of interactions between population, industrial growth, food production and limits in the ecosystems of the Earth. It was originally produced and used by a Club of Rome study that produced the model and the book The Limits to Growth...

.

Food supply and consumption


Carrying capacity, at its most basic level, is about organisms and food supply, where "X" amount of humans need "Y" amount of food to survive. If the humans neither gain or lose weight in the long run, the calculation is fairly accurate. If the quantity of food is invariably equal to the "Y" amount, carrying capacity has been reached. Humans, with the need to enhance their reproductive success (see Richard Dawkins' The Selfish Gene
The Selfish Gene
The Selfish Gene is a book on evolution by Richard Dawkins, published in 1976. It builds upon the principal theory of George C. Williams's first book Adaptation and Natural Selection. Dawkins coined the term "selfish gene" as a way of expressing the gene-centred view of evolution as opposed to the...

), understand that food supply can vary and also that other factors in the environment can alter humans' need for food. A house, for example, might mean that one does not need to eat as much to stay warm as one otherwise would. Over time, monetary transactions have replaced barter and local production, and consequently modified local human carrying capacity. However, purchases also impact regions thousands of miles away. For example, carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...

 from an automobile
Automobile
An automobile, autocar, motor car or car is a wheeled motor vehicle used for transporting passengers, which also carries its own engine or motor...

 travels to the upper atmosphere. This led Paul R. Ehrlich
Paul R. Ehrlich
Paul Ralph Ehrlich is an American biologist and educator who is the Bing Professor of Population Studies in the department of Biological Sciences at Stanford University and president of Stanford's Center for Conservation Biology. By training he is an entomologist specializing in Lepidoptera , but...

 to develop the IPAT equation
I = P * A * T

where:
I is the impact on the environment resulting from consumption
P is the population number
A is the consumption per capita (affluence)
T is the technology factor


Technology is an important factor in the dynamics of carrying capacity. For example, the Neolithic
Neolithic
The Neolithic Age, Era, or Period, or New Stone Age, was a period in the development of human technology, beginning about 9500 BC in some parts of the Middle East, and later in other parts of the world. It is traditionally considered as the last part of the Stone Age...

 revolution increased the carrying capacity of the world relative to humans through the invention of agriculture. Currently, the use of fossil fuels has artificially increased the carrying capacity of the world by the use of stored sunlight, albeit at many other expenses. Other technological advances that have increased the carrying capacity of the world relative to humans are: polders, fertilizer
Fertilizer
Fertilizer is any organic or inorganic material of natural or synthetic origin that is added to a soil to supply one or more plant nutrients essential to the growth of plants. A recent assessment found that about 40 to 60% of crop yields are attributable to commercial fertilizer use...

, composting, greenhouses, land reclamation
Land reclamation
Land reclamation, usually known as reclamation, is the process to create new land from sea or riverbeds. The land reclaimed is known as reclamation ground or landfill.- Habitation :...

, and fish farming
Fish farming
Fish farming is the principal form of aquaculture, while other methods may fall under mariculture. Fish farming involves raising fish commercially in tanks or enclosures, usually for food. A facility that releases young fish into the wild for recreational fishing or to supplement a species'...

.

Agricultural capability on Earth expanded in the last quarter of the 20th century. But now there are many projections of a continuation of the decline in world agricultural capability (and hence carrying capacity) which began in the 1990s. Most conspicuously, China's food production is forecast to decline by 37% by the last half of the 21st century, placing a strain on the entire carrying capacity of the world, as China's population could expand to about 1.5 billion people by the year 2050. This reduction in China's agricultural capability (as in other world regions) is largely due to the world water crisis
Water crisis
Water crisis is a general term used to describe a situation where the available water within a region is less than the region's demand. The term has been used to describe the availability of potable water in a variety of regions by the United Nations and other world organizations...

 and especially due to mining groundwater
Groundwater
Groundwater is water located beneath the ground surface in soil pore spaces and in the fractures of rock formations. A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water. The depth at which soil pore spaces or fractures and voids in rock...

 beyond sustainable yield, which has been happening in China since the mid-20th century.

Ecological footprint


One way to estimate human demand compared to ecosystem's carrying capacity is "Ecological Footprint
Ecological footprint
The ecological footprint is a measure of human demand on the Earth's ecosystems. It is a standardized measure of demand for natural capital that may be contrasted with the planet's ecological capacity to regenerate. It represents the amount of biologically productive land and sea area necessary to...

" accounting. Rather than speculating about future possibilities and limitations imposed by carrying capacity constraints, Ecological Footprint accounting provides empirical, non-speculative assessments of the past. It compares historically regeneration rates (biocapacity) against historical human demand (Ecological Footprint) in the same year. One result shows that humanity's demand for 1999 exceeded the planet's biocapacity for 1999 by over 20 percent.

In tourism



Tourism carrying capacity is a now antiquated approach to managing visitors in protected areas and national parks which evolved out of the fields of range, habitat and wildlife management. In these fields, managers attempted to determine the largest population of a particular species that could be supported by a habitat over a long period of time.

See also


  • Arable land
    Arable land
    In geography and agriculture, arable land is land that can be used for growing crops. It includes all land under temporary crops , temporary meadows for mowing or pasture, land under market and kitchen gardens and land temporarily fallow...

  • Asymmetry Principle
    Asymmetry Principle
    The Asymmetry Principle was developed by economist Peter Tertzakian, and was first presented in his book The End of Energy Obesity published in 2009. Historically, each energy crisis has brought society to a solutions crossroad: find more or use less...

  • Biocapacity
    Biocapacity
    Biocapacity is the capacity of an area to provide resources and absorb wastes. When the area's ecological footprint exceeds its biocapacity, unsustainability occurs....

  • Ecological footprint
    Ecological footprint
    The ecological footprint is a measure of human demand on the Earth's ecosystems. It is a standardized measure of demand for natural capital that may be contrasted with the planet's ecological capacity to regenerate. It represents the amount of biologically productive land and sea area necessary to...

  • Environmental space
    Environmental space
    The concept of environmental space is the amount of any particularresource that can be consumed by a country without threatening the continuedavailability of that resource, assuming that everyone in the world is...

  • List of countries by fertility rate
  • Lotka–Volterra equation
  • Over-consumption
    Over-consumption
    Over-consumption is a situation where resource-use has outpaced the sustainable capacity of the ecosystem. A prolonged pattern of overconsumption leads to inevitable environmental degradation and the eventual loss of resource bases...

  • Overpopulation
    Overpopulation
    Overpopulation is a condition where an organism's numbers exceed the carrying capacity of its habitat. The term often refers to the relationship between the human population and its environment, the Earth...

  • Overpopulation in wild animals
    Overpopulation in wild animals
    Overpopulation in wild animals occurs when a population of a wild species exceeds the carrying capacity of its ecological niche. Overpopulation is a function of the number of individuals compared to the relevant resources, such as the water and essential nutrients they need to survive.In the...

  • Population
    Population
    A population is all the organisms that both belong to the same group or species and live in the same geographical area. The area that is used to define a sexual population is such that inter-breeding is possible between any pair within the area and more probable than cross-breeding with individuals...

  • Population ecology
    Population ecology
    Population ecology is a sub-field of ecology that deals with the dynamics of species populations and how these populations interact with the environment. It is the study of how the population sizes of species living together in groups change over time and space....

  • Population growth
    Population growth
    Population growth is the change in a population over time, and can be quantified as the change in the number of individuals of any species in a population using "per unit time" for measurement....

  • r/K selection theory
    R/K selection theory
    In ecology, r/K selection theory relates to the selection of combinations of traits in an organism that trade off between quantity or quality of offspring...

  • Simon–Ehrlich wager
  • Thomas Malthus
    Thomas Malthus
    The Reverend Thomas Robert Malthus FRS was an English scholar, influential in political economy and demography. Malthus popularized the economic theory of rent....

  • Tourism carrying capacity
    Tourism carrying capacity
    Tourism carrying capacity is a now antiquated approach to managing visitors in protected areas and national parks which evolved out of the fields of range, habitat and wildlife management. In these fields, managers attempted to determine the largest population of a particular species that could be...

  • Toxic capacity
    Toxic capacity
    Toxic capacity can mean the toxicity of a substance, possibly in relation to a specific organism and toxic capacity can mean the capacity of an organism, organic system or ecosystem to contain a toxic substance or a selection of toxic substances without showing signs of poisoning or dying.-Toxic...



External links

  • http://www.unfpa.org/public/
  • http://www.isleroyalewolf.org/
  • http://www.optimumpopulation.org
  • http://www.DieOff.org
  • http://www.hartford-hwp.com/archives/24/042.html
  • http://www.carryingcapacity.org
  • http://atlas.aaas.org/index.php?part=1&sec=trends