Overpopulation occurs when a species' population exceeds the carrying capacity of its ecological niche. It can result from an increase in births (fertility rate), a decline in the mortality rate, an increase in immigration, or an unsustainable biome and depletion of resources. When overpopulation occurs, individuals limit available resources to survive.
The change in number of individuals per unit area in a given locality is an important variable that has a significant impact on the entire ecosystem.
In the wild, overpopulation often causes growth in the populations of predators. This has the effect of controlling the prey population and ensuring its evolution in favor of genetic characteristics that render it less vulnerable to predation (and the predator may co-evolve, in response).
In the absence of predators, species are bound by the resources they can find in their environment, but this does not necessarily control overpopulation, at least in the short term. An abundant supply of resources can produce a population boom followed by a population crash. Rodents such as lemmings and voles have such cycles of rapid population growth and subsequent decrease. Snowshoe hares populations similarly cycled dramatically, as did those of one of their predators, the lynx.
The introduction of a foreign species has often caused ecological disturbance, as when deer and trout were introduced into Argentina when rabbits were introduced to Australia, and indeed when predators such as cats were introduced in turn to attempt to control the rabbits.
Human overpopulation occurs when the ecological footprint of a human population in a specific geographical location exceeds the carrying capacity of the place occupied by that group. Overpopulation can further be viewed, in a long term perspective, as existing when a population cannot be maintained given the rapid depletion of non-renewable resources or given the degradation of the capacity of the environment to give support to the population.
The term human overpopulation also refers to the relationship between the entire human population and its environment: the Earth, or to smaller geographical areas such as countries. Overpopulation can result from an increase in births, a decline in mortality rates against the background of high fertility rates, an increase in immigration, or an unsustainable biome and depletion of resources. It is possible for very sparsely populated areas to be overpopulated if the area has a meagre or non-existent capability to sustain life (e.g. a desert). Advocates of population moderation cite issues like quality of life, carrying capacity and risk of starvation as a basis to argue against continuing high human population growth and for population decline. Scientists suggest that the human impact on the environment as a result of overpopulation, profligate consumption and proliferation of technology has pushed the planet into a new geological epoch known as the Anthropocene.
When is an area overpopulated? When its population can not be maintained without rapidly depleting non-renewable resources  (or converting renewable resources into non-renewable ones) and without decreasing the capacity of the environment to support the population. In short, if the long-term carrying capacity of an area is clearly being degraded by its current human occupants, that area is overpopulated.
Four referendums were held in Switzerland in 1974. The first was held on 20 October on a popular initiative "against foreign infiltration and overpopulation", and was rejected by voters. The next three were held on 8 December on an amendment to the federal budget (rejected), restricting federal expenditure (approved) and a popular initiative (and counterproposal) on social health insurance (both of which were rejected).Birth credit
A "choice-based, marketable, birth license plan" or "birth credits" for population control has been promoted by urban designer and environmental activist Michael E. Arth since the 1990s. Previous iterations of similar transferable birth licensing schemes can also be traced to economist Kenneth Boulding (1964) and leading ecological economist and steady-state theorist Herman Daly (1991)Arth offers birth credits in the place of solutions to human overpopulation that may take too long (like economic development and traditional family planning), are impractical (like space colonization), or cruel (like forced sterility, genocide, famine, disease, and war).Carrying capacity
The carrying capacity of a biological species in an environment is the maximum population size of the species that the environment can sustain indefinitely, given the food, habitat, water, and other necessities available in the environment.
In population biology, carrying capacity is defined as the environment's maximal load, which is different from the concept of population equilibrium. Its effect on population dynamics may be approximated in a logistic model, although this simplification ignores the possibility of overshoot which real systems may exhibit.
Carrying capacity was originally used to determine the number of animals that could graze on a segment of land without destroying it. Later, the idea was expanded to more complex populations, like humans. For the human population, more complex variables such as sanitation and medical care are sometimes considered as part of the necessary establishment. As population density increases, birth rate often increases and death rate typically decreases. 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 concerned, but can include insufficient space, food supply, or sunlight. 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, 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" 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 US Senate.Elysium (film)
Elysium is a 2013 American science fiction action film produced, written, and directed by Neill Blomkamp. It stars Matt Damon, Jodie Foster, Alice Braga, and Sharlto Copley. The film takes place on both a ravaged Earth, and a luxurious space habitat (Stanford torus design, one of the proposed NASA designs) called Elysium. The film itself offers deliberate social commentary which explores political and sociological themes such as immigration, overpopulation, transhumanism, health care, worker exploitation, the justice system, and social class issues. The basic plot is similar to the Star Trek: The Original Series episode "The Cloud Minders" and to the classic Metropolis. The film was released on August 9, 2013 by TriStar Pictures, in both conventional and IMAX Digital theaters. It was a modest success and received generally positive reviews from critics, even though many considered it a disappointment after Blomkamp's first film District 9. Elysium was released on DVD and Blu-ray on December 17, 2013.Human impact on the environment
Human impact on the environment or anthropogenic impact on the environment includes changes to biophysical environments and ecosystems, biodiversity, and natural resources caused directly or indirectly by humans, including global warming, environmental degradation (such as ocean acidification), mass extinction and biodiversity loss, ecological crisis, and ecological collapse. Modifying the environment to fit the needs of society is causing severe effects, which become worse as the problem of human overpopulation continues. Some human activities that cause damage (either directly or indirectly) to the environment on a global scale include human reproduction, overconsumption, overexploitation, pollution, and deforestation, to name but a few. Some of the problems, including global warming and biodiversity loss pose an existential risk to the human race, and overpopulation causes those problems.The term anthropogenic designates an effect or object resulting from human activity. The term was first used in the technical sense by Russian geologist Alexey Pavlov, and it was first used in English by British ecologist Arthur Tansley in reference to human influences on climax plant communities. The atmospheric scientist Paul Crutzen introduced the term "Anthropocene" in the mid-1970s. The term is sometimes used in the context of pollution emissions that are produced from human activity but also applies broadly to all major human impacts on the environment. Many of the actions taken by humans that contribute to a heated environment stem from the burning of fossil fuel from a variety of sources, such as: electricity, cars, planes, space heating, manufacturing, or the destruction of forests.Human overpopulation
Human overpopulation (or population overshoot) is when there are too many people for the environment to sustain (with food, drinkable water, breathable air, etc.). In more scientific terms, there is overshoot when the ecological footprint of a human population in a geographical area exceeds that place's carrying capacity, damaging the environment faster than nature can repair it, potentially leading to an ecological and societal collapse. Overpopulation could apply to the population of a specific region, or to world population as a whole.Overpopulation can result from an increase in births, a decline in mortality rates, an increase in immigration, or an unsustainable biome and depletion of resources. It is possible for very sparsely populated areas to be overpopulated if the area has a meagre or non-existent capability to sustain life (e.g. a desert).
Advocates of population moderation cite issues like exceeding the Earth's carrying capacity, global warming, potential or imminent ecological collapse, impact on quality of life, and risk of mass starvation or even extinction as a basis to argue for population decline.
A more controversial definition of overpopulation, as advocated by Paul Ehrlich, is a situation where a population is in the process of depleting non-renewable resources. Under this definition, changes in lifestyle could cause an overpopulated area to no longer be overpopulated without any reduction in population, or vice versa.Scientists suggest that the overall human impact on the environment, due to overpopulation, overconsumption, pollution, and proliferation of technology, has pushed the planet into a new geological epoch known as the Anthropocene.List of environmental issues
This is an alphabetical list of environmental issues, harmful aspects of human activity on the biophysical environment. They are loosely divided into causes, effects and mitigation, noting that effects are interconnected and can cause new effects.Overpopulation in domestic pets
Overpopulation in domestic pets is the surplus of pets, such as cats, dogs, and exotic animals. In the United States, six to eight million animals are brought to shelters each year, of which an estimated three to four million are subsequently euthanized, including 2.7 million considered healthy and adoptable. Euthanasia numbers have declined from the 1970s, when U.S. shelters euthanized an estimated 12 to 20 million animals. Most humane societies, animal shelters and rescue groups urge animal caregivers to have their animals spayed or neutered to prevent the births of unwanted and accidental litters that could contribute to this dynamic.Physiological density
The physiological density or real population density is the number of people per unit area of arable land.
A higher physiological density suggests that the available agricultural land is being used by more and may reach its output limit sooner than a country that has a lower physiological density. Egypt is a notable example, with physiological density reaching that of Bangladesh, despite much desert.Population Connection
Population Connection (formerly Zero Population Growth or ZPG) is a non-profit organization in the United States that raises awareness of population challenges and advocates for improved global access to family planning and reproductive health care. The organization was founded in 1968 by Paul R. Ehrlich, Richard Bowers and Charles Remington in the wake of Ehrlich's best-selling book, The Population Bomb. The organization adopted its current name in 2002.Population Research Institute
The Population Research Institute (PRI) is a non-profit organization based in Front Royal, Virginia, USA. PRI describes itself as "a non-profit research group whose goals are to expose the myth of overpopulation" as well as "human rights abuses committed in population control programs, and to make the case that people are the world's greatest resource." It operates programs against the advancement of contraception, sterilization, and abortion. PRI is a 501(c)(3) organization and claims contacts to pro-life groups in over 30 countries. Results are being released in an own online periodical, PRI Review.Population density
Population density (in agriculture: standing stock and standing crop) is a measurement of population per unit area or unit volume; it is a quantity of type number density. It is frequently applied to living organisms, and most of the time to humans. It is a key geographical term. In simple terms population density refers to the number of people living in an area per kilometer square.Population dynamics
Population dynamics is the branch of life sciences that studies the size and age composition of populations as dynamical systems, and the biological and environmental processes driving them (such as birth and death rates, and by immigration and emigration). Example scenarios are ageing populations, population growth, or population decline.Soylent Green
Soylent Green is a 1973 American dystopian thriller film directed by Richard Fleischer and starring Charlton Heston and Leigh Taylor-Young. Edward G. Robinson appears in his final film. Loosely based on the 1966 science fiction novel Make Room! Make Room! by Harry Harrison, it combines both police procedural and science fiction genres; the investigation into the murder of a wealthy businessman and a dystopian future of dying oceans and year-round humidity due to the greenhouse effect, resulting in suffering from pollution, poverty, overpopulation, euthanasia and depleted resources.In 1973 it won the Nebula Award for Best Dramatic Presentation and the Saturn Award for Best Science Fiction Film.The Human Factor (2002 The Outer Limits)
"The Human Factor" is an episode of the television show The Outer Limits. It first aired January 11, 2002, in the show's seventh season.The Population Bomb
The Population Bomb is a best-selling book written by Stanford University Professor Paul R. Ehrlich and his wife, Anne Ehrlich (who was uncredited), in 1968. It predicted worldwide famine in the 1970s and 1980s due to overpopulation, as well as other major societal upheavals, and advocated immediate action to limit population growth. Fears of a "population explosion" were widespread in the 1950s and 1960s, but the book and its author brought the idea to an even wider audience.
The book has been criticized since its publishing for its alarmist tone, and in recent decades for its inaccurate predictions. The Ehrlichs stand by the basic ideas in the book, stating in 2009 that "perhaps the most serious flaw in The Bomb was that it was much too optimistic about the future" and believe that it achieved their goals because "it alerted people to the importance of environmental issues and brought human numbers into the debate on the human future."Voluntary Human Extinction Movement
The Voluntary Human Extinction Movement (VHEMT) is an environmental movement that calls for all people to abstain from reproduction to cause the gradual voluntary extinction of humankind. VHEMT supports human extinction primarily because, in the group's view, it would prevent environmental degradation. The group states that a decrease in the human population would prevent a significant amount of human-caused suffering. The extinctions of non-human species and the scarcity of resources required by humans are frequently cited by the group as evidence of the harm caused by human overpopulation.
VHEMT was founded in 1991 by Les U. Knight, an American activist who became involved in the environmental movement in the 1970s and thereafter concluded that human extinction was the best solution to the problems facing the Earth's biosphere and humanity. Knight publishes the group's newsletter and serves as its spokesman. Although the group is promoted by a website and represented at some environmental events, it relies heavily on coverage from outside media to spread its message. Many commentators view its platform as unacceptably extreme, though other writers have applauded VHEMT's perspective. In response to VHEMT, some journalists and academics have argued that humans can develop sustainable lifestyles or can reduce their population to sustainable levels. Others maintain that, whatever the merits of the idea, the human reproductive drive will prevent humankind from ever voluntarily seeking extinction.World population
In demographics, the world population is the total number of humans currently living, and was estimated to have reached 7.7 billion people as of April 2019. It took over 200,000 years of human history for the world's population to reach 1 billion; and only 200 years more to reach 7 billion.The world population has experienced continuous growth following the Great Famine of 1315–1317 and the end of the Black Death in 1350, when it was near 370 million.
The highest global population growth rates, with increases of over 1.8% per year, occurred between 1955 and 1975—peaking to 2.1% between 1965 and 1970. The growth rate declined to 1.2% between 2010 and 2015 and is projected to decline further in the course of the 21st century. However, the global population is still increasing and is projected to reach about 10 billion in 2050 and more than 11 billion in 2100.Total annual births were highest in the late 1980s at about 139 million, and as of 2011 were expected to remain essentially constant at a level of 135 million, while deaths numbered 56 million per year and were expected to increase to 80 million per year by 2040.
The median age of the world's population was estimated to be 30.4 years in 2018.