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Human overpopulation

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Template:Totallydisputed Overpopulation occurs when the population of a living species exceeds the carrying capacity of its ecological niche. In common parlance, the term usually refers to the relationship between the human population and its environment, Earth.

Overpopulation is not a function of the number or density of the individuals, but rather the number of individuals compared to the resources they need to survive. In other words, it is a ratio: population over resources. If a given environment has a population of 10, but there is food and drinking water enough for only 9 people, then that environment is overpopulated, while if the population is 100 individuals but there are food and water enough for 200, then it is not overpopulated.

Overpopulation can result from increases in births, a decline in mortality rates, which is linked to increases in life expectancy, or from an unsustainable use and depletion of resources. Advances in technology can reduce the threat of overpopulation by making new resources available, or by increasing the productivity of existing resources.

Resources to be taken into account when estimating if an ecological niche is overpopulated include clean water and air, food, shelter, warmth, or other issues related to survival. In the case of human beings, there are others such as arable land and, for all but tribes with primitive lifestyles, lesser resources such as employment, money or other economic resources, education, fuel, electricity, healthcare, proper sewage treatment and waste management, and transportation. The problem of waste may yet prove the most serious danger of overpopulation.

In the context of human societies, overpopulation occurs when the population density is so great as to actually cause an impaired quality of life, environmental degradation, or a long-term shortages of essential goods and services. Sometimes, overpopulation is not necessarily an imbalance between the number of individuals compared to the resources they need to survive, or a ratio of population over resources. This is because such an imbalance may be caused by any other number of factors such as bad governance, war, injustice and exploitation, etc. When other such factors come into play in a certain locale, and population density cannot be shown to be the major cause, overpopulation cannot be conclusively said to occur.

The world's human population has quadrupled in the course of the last hundred years. It is currently growing by more than 75 million people per year, down from a peak numerical growth of about 88 million per year in the late 1980s. About half the world lives in nations with sub-replacement fertility, and population growth in those countries is due to immigration.

Malthus' theory

Thomas Malthus argued in An Essay on the Principle of Population, first published in 1798, that if left unrestricted, human populations would continue to grow until they would become too large to be supported by the food grown on available agricultural land. He proposed that, while resources tend to grow linearly, population grows exponentially. At that point, the population would be restrained through mass famine and starvation. Malthus argued for population control, through "moral restraint", to avoid this happening. As the population of a species exceeds the amount of available resources, it decreases, sometimes sharply, since the lack of resources causes mortality (deaths) to increase. This process keeps the population in check and ensures it doesn't exceed the amount of resources.

Over the two hundred years which followed, famine has overtaken numerous individual regions; proponents of this theory state that these famines were examples of Malthusian catastrophes. On a global scale, however, food production has grown faster than population. It has often been argued that future pressures on food production, combined with threats to other aspects of the earth's habitat such as global warming, make overpopulation a still more serious threat in the future. Perhaps the best-known example of such an argument is The Limits to Growth, a report produced for the Club of Rome in the early 1970s. More recent examples also exist [1].

Population as a function of food availability

Recent research and experiments [2] attack the contemporary belief that human populations are a naturally explosive independent variable. Thinkers such as David Pimentel, a professor from Cornell University, Alan Thornhill, Russell Hopffenberg and author Daniel Quinn propose that like other animals, human populations predictably grow and shrink according to their available food supply – populations grow in an abundance of food, and shrink in times of scarcity.

Proponents of this theory indicate that every time food production is intensified to feed a growing population, the population responds by increasing even more. Some human populations throughout history support this theory, as consistent population growth began with the Neolithic Revolution, followed by subsequent agricultural revolutions, and thus food supply began consistently increasing and continues to do so in the present. This can be observed in cultural contexts, as populations of hunter-gatherers fluctuate in accordance with the amount of available food and are significantly smaller than populations of agriculturalists, who increase the amount of food available by putting more land under agriculture.

Critics of this idea point out that birth rates are lowest in developed nations, which also have the highest access to food. In fact, some developed countries have both a diminishing population and an abundant food supply (Italy and Japan). Thus human populations do not always grow to match the available food supply. Factors cited in the decline of birth rates include such social factors: increased access to contraception; later ages of marriage; the growing desire of many women in such settings to seek careers outside of child rearing and domestic work; and the decreased need of children in industrialized settings. The latter explanation stems from the fact that children perform a great deal of work in small-scale agricultural societies, and work less in industrial ones; it has been cited to explain the drop-off in birth rates worldwide in all industrializing regions.

Food production has outpaced population growth, meaning that there is now more food available per person than ever before in history (although as with other resources this is distributed very unequally; rich nations have a super-abundance of food, while poor nations often suffer famines). Studies project that food production can continue to increase until at least 2050. At the same time, world population is predicted to slow its growth, reaching 9.1 billion by 2050 in the median scenario. Net growth by mid century is predicted to be 34 million per year in contrast to the roughly 76 million per year that was seen from 2000 to 2005. [3] Another United Nations report projects that world population will peak at 9.2 billion around 2075 [4][5].

Population projections

United Nation's medium variant population projections by location.

According to projections by the Population Division of the United Nations revised in 2004 [6], the population of the world will stabilize at 9.1 billion by 2050 due to demographic transition. The UN has consistently revised its population projections downwards over the last 10 years. Birth rates are now falling in most developing countries, while the population in many developed countries would also fall without immigration [7].

David Pimentel, a professor of ecology and agricultural sciences at Cornell University, predicts that population outcomes for the 22nd century range from 2 billion people (characterised as thriving in harmony with the environment), to 12 billion people (characterised as miserable and suffering a difficult life with limited resources and widespread famine). [8]

Optimistic viewpoints on population growth

Other studies have countered with the claim that the current population level of over six billion may be supported by current resources, or that the global population may grow to ten billion and still be within the Earth's carrying capacity. In The Skeptical Environmentalist, published in 2001, Bjørn Lomborg argued that because of the falling rate of population growth, and because of new, alternative technologies, there is no problem with overpopulation. The assumptions that underlie these claims, however, have been strongly criticised. One criticism is that poor people can't afford such technologies. However, it is also possible the Earth is capable of sustaining more humans without the need for such technology. For example, meat production is very energy inefficient. Food availability would increase if protein sources like soybeans were used instead. However, given the extremely low probability of everyone in the rich nations suddenly desiring to eat soybeans, this argument is rather specious.

In any case, many proponents of population control have averred that famine is far from being the only problem attendant to overpopulation. They point out that ultimate shortages of certain fossil fuels (see Hubbert peak theory), as well as the incidence of serious communicable diseases in dense populations, and war casualties over scarce resources such as fertile arable land, petroleum, and potable water sources all increase in severity along with increasing population.

A shortage of arable land is a problem. About 21% of the earth's land is arable. In the past, 160 acres (650,000 m²) of farm land crops fed one person. Hydroponics in autonomous building gardens and greenhouses grow more food in less space, although the requirement for fresh water may limit this technology. Most food production experiments have used vegetable farming because it can support an adult from as little as 15 m² of land. High crop yield vegetables like potatoes and lettuce do not waste space with inedible plant parts, like stalks, husks, vines, and inedible leaves. New varieties of selectively bred and hybrid plants have larger edible parts (fruit, vegetable, grain) and smaller inedible parts. With new technologies, it is now possible to grow crops on some unarable land under certain conditions. Aquaculture could theoretically dramatically increase available area. Hydroponics and food from bacteria and fungi, like Quorn, may allow the growing of food without having to consider land quality, climate, or even available sunlight, although such a process may be very energy-intensive.

It is hoped that technologies and methods which follow the concepts of sustainability will allow better lives for more people. This viewpoint is typically named cornucopian.

Effects of overpopulation

The world's current agricultural production, if it were distributed evenly, would be sufficient to feed everyone living on the Earth today. However, many critics hold that, in the absence of other measures, simply feeding the world's population well would only make matters worse, natural growth will cause the population to grow to unsustainable levels, and will result directly in famines and deforestation and indirectly in pandemic disease and war.

Some other problems characteristic of human overpopulation:

  • Mass extinctions of plants and animals as habitats are used for farming and human settlements
  • Rapid depletion of natural resources
  • Increased levels of pollution
  • Deforestation and loss of ecosystems that sustain global atmospheric oxygen and carbon dioxide balance
  • Possible changes in atmospheric composition and consequent global warming
  • Potential increases in desertification of arable land
  • People struggling to live under poor conditions
  • Low birth rate due to the inability of mothers to get enough resources to sustain a baby from fertilization to birth
  • Low life expectancy
  • Low level of literacy
  • High rate of unemployment in urban areas (leading to social problems)
  • Insufficient arable land
  • Little surplus food
  • Poor diet with ill health and diet-deficiency diseases (e.g. rickets)
  • Low Per Capita GDP
  • Low level of capital formation
  • Unhygienic living conditions for many
  • Economically stretched government
  • High crime from people who steal resources to survive
  • Rising tensions over scarce resources possibly leading to warfare and other armed conflict
  • Decreasing human population towards equilibrium
  • Inflationary pressures
  • Increase in the dependency burden due to the greater number of younger people in the population

The demographic transition

However, others contend that within a generation after the standard of living and life expectancy starts increasing, family sizes start dropping in what is termed the demographic transition. In support they point to the contention that every estimate of maximum global population since the 1960s, when the "population explosion" became a worry, has been significantly lower than the previous estimates. Among those holding this view are the ecologist Paul Colinvaux, who writes on the topic in Why Big Fierce Animals are Rare, and The Fates of Nations.

Today about half the world lives in nations with sub-replacement fertility. All the nations of East Asia, with the exceptions of Mongolia, the Philippines, and Laos are below this level. Russia and Eastern Europe are in most cases quite dramatically below replacement fertility. Western Europe also is below replacement. In the Middle East Iran, Tunisia, Algeria, Turkey, and Lebanon are below replacement. Canada, Australia, and New Zealand are similar to Western Europe, while the United States is just barely below replacement with about 2.0 births per woman. All four of these nations still have growing populations due to high rates of immigration. The countries having the lowest fertility are Hong Kong, Macao, Singapore and Lithuania.

Demographic Entrapment

"Demographic entrapment" is a concept developed by Maurice King that has not gained acceptance. King describes a country stuck in an early stage of the demographic transition, with a persistently high birth rate despite economic growth and/or increased life expectancy. Many sub-saharan countries are quoted as examples of demographic entrapment - one of these would be Uganda, where the total fertility rate stands at 6.71 children born per women, even though the economy has shown steady growth since 1990 and life expectancy stands at 53 ((figures from the 2006 edition of the CIA world factbook). Other African countries, such as Zimbabwe, have seen their population growth slow down, but not stop, on account of a decrease in life expectancy and an increase in emigration, with the birth rate remaining high - the democratic transition in reverse[9].

The status of women

Another point of view on population versus the standard of living is that of Virginia Abernethy in Population Politics, in which she claims that this effect only holds true in nations where women enjoy a special status. In strongly patriarchal nations, where she claims women enjoy few special rights, a high standard of living tends to result in population growth. She argues that foreign aid to poor countries must include significant components designed to improve the education, human rights, political rights, political power, and also to equalize the economic and sexual status and power of women.

Her theory runs counter to some of the available empirical evidence. For example Iran had a Total Fertility Rate of 1.82 children per couple in 2005, which is below the replacement rate of 2.1 to 2.3 children per couple needed to maintain population. Iran is widely perceived as a patriarchal nation, and yet any population growth that occurred there came not from increased birth rates, but from decreased mortality rates, i.e. not from a lack of reproductive rights.

"Survival of the fittest"

Some approach overpopulation with a "survival of the fittest," attitude, arguing that if the Earth's ecosystem becomes overtaxed, it will naturally regulate itself. In this mode of thought, disease or starvation are natural means of lessening population. Two particular objections to this argument are that a) in the meantime, a huge number of plant and animal species will be made extinct, reducing biodiversity and b) the huge and unnecessary amount of human suffering that would result is inhumane and completely avoidable.


Others argue that economic development is the best way to reduce population growth (see demographic transition). Many developed countries in the world today, such as Italy, now have declining populations (ignoring the effects of immigration).

Medicine shortages

The largest shortage for important resources is of medicine. A shortage of educated people can lead to a shortage of doctors. Fewer doctors in a population causes the price of medical services to rise. This can either cause a government subsidised healthcare system to be unsustainable, or lead to increased medical bills and health insurance costs.

Fossil-fuel subsidies in agriculture

One of the strongest criticisms of an optimistic outlook is that of the fossil fuel subsidy of modern agriculture. The extremely high agricultural outputs of modern farms depend entirely on immense fossil fuel (mostly petroleum) subsidies in the forms of fertilizers, equipment fuel, and other chemicals such as pesticides. There is much discussion regarding a future peak in oil production and its consequences. See Hubbert peak and Future energy development. However, most of the worlds population uses some to no fossil fuels at all, although it is expected that consumption of these fuels will increase as those nations develop (especially India and China).

Overpopulation as a social issue

The density of population has an impact on a broad range of social and economic issues, such as land prices and housing costs. For example, relatively densely populated countries such as Japan have higher land prices than less densely populated countries such as Australia, and even in that country, land prices have doubled and redoubled as the population has increased. It is sometimes argued that reducing the populations of some areas, such as large cities, would have positive benefits for these reasons.

Overpopulation as a theme in fiction

In 1729, Johnathan Swift wrote the satirical essay "A Modest Proposal" where he suggests one solution for both the problem of overpopulation and the growing numbers of undernourished people in Ireland can be solved by the breeding of infants as food.

Science fiction writers have frequently made famous predictions in which they portrayed dystopian futures in which the world has become massively overpopulated. This became a major theme in the 1950s and 1960s. One of the first depictions of future megacities was The Caves of Steel by Isaac Asimov (1954). The 1960s saw increasing anxiety about the prospect of the exponential growth of world population, underscored by the publication of Paul R. Ehrlich's non-fiction The Population Bomb, in 1968.

In the same year, John Brunner's science-fictional Stand on Zanzibar was published. This is perhaps the definitive overpopulation novel to date, though others such as Harry Harrison's Make Room! Make Room! also became a powerful movie (Soylent Green). Logan's Run is a novel by William F. Nolan and George Clayton Johnson (1967), describing a dystopian future society in which the population is kept young by euthanizing everyone who reaches a certain age, thus neatly avoiding the problem of overpopulation. A 1972 film called Z.P.G. featured an overpopulated, very polluted future Earth, whose world government practices Zero Population Growth, executing persons who violate the 30-year ban on procreation.

J. G. Ballard's story "Billennium" pictures a future in which every individual has four, then just three, square metres of living space. Frederik Pohl in "The Space Merchants" described a future in which even public staircases are rented out as living spaces. Robert Silverberg's The World Inside imagines a future with mile high towers holding a million people each. James Blish and Norman L. Knight in A Torrent of Faces imagine a nightmarish future of 1,000 billion living in just 100,000 cities on Earth.

From the 1980s, there has been an evident lessening of such fears in science fiction. Cyberpunk fiction, such as that of William Gibson, often depicts huge, sprawling cities. Yet these are as remarkable for their energy and diversity as for their more dystopian characteristics.

Population projections in space

Space advocists and others have made various projections regarding future human population growth in space.

Even as far back as 1798, Thomas Malthus stated in An Essay on the Principle of Population:

"The germs of existence contained in this spot of earth, with ample food, and ample room to expand in, would fill millions of worlds in the course of a few thousand years."

Gerard O'Neill has suggested that, taking the completion of his proposed Island One as year zero, maximum population growth could then result in a population of 7.3 billion within 35 years.

Marshall Savage (1992, 1994) has projected a population of five Qintillion throughout the solar system by 3000, with the majority in the asteroid belt. Clarke, a fervent supporter of Savage, now argues that by 2057 there will be humans on the Moon, Mars, Europa, Ganymede, Titan and in orbit around Venus, Neptune and Pluto.

Freeman Dyson (1999) favours the Kuiper belt as the future home of humanity, suggesting this could happen within a few centuries.

K. Eric Drexler, famous inventor of the futuristic concept of Molecular Nanotechnology, has suggested in Engines of Creation that colonising space will mean breaking the Malthusian limits to growth forever for the human species.

Considered to be the most mind boggling prediction is that of John S. Lewis in Mining the Sky. Bordering on the overpopulation of the solar system itself, Lewis suggests that the staggering resources of the solar system could support 10 quadrillion (10^15) people.

Many authors (eg. Carl Sagan, Arthur C. Clarke, Isaac Asimov) have argued that shipping the excess population into space is no solution to human overpopulation, saying that (Clarke, 1999) "the population battle must be fought or won here on Earth." It is not the lack of resources in space that they see as the problem (as books such as Mining the sky demonstrate); it is the sheer physical impracticality of shipping vast numbers of people into space to "solve" overpopulation on Earth that these authors and others regards as absurd.

References

See also

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