Human overpopulation: Difference between revisions

Map of countries by population (See List of countries by population.)

File:Pop density.jpg

Areas of high population densities, calculated in 1994.

Overpopulation is the condition of any organism's numbers exceeding the carrying capacity of its ecological niche. In common parlance, the term usually refers to the relationship between the human population and its environment, the Earth.

Introduction

Overpopulation is not simply a function of the number or density of the individuals, but rather the number of individuals compared to the resources (for example, food production or water resources) needed for survival or well-being. Overpopulation is the ratio of population divided by resources. If a given environment has a population of ten, but there is food and drinking water enough for only nine, then that environment is overpopulated; if the population is 100 individuals but there is food and water enough for 200, then it is not overpopulated. Overpopulation can result from increases in births, a decline in mortality rates due to medical advancements, or from an unsustainable use and depletion of resources. It is possible for very sparsely-populated areas to be "overpopulated", as the area in question may have very meager or non-existent capability to sustain human life (e.g. the middle of the Sahara desert).

If looking only at survival, then resources to be taken into account when evaluating when an ecological niche is overpopulated include clean water, air, food, shelter, warmth, or other resources related to survival.

If looking at well-being of human beings, there are additional resources to be considered, such medical care, employment, money, education, fuel, electricity, healthcare, proper sewage treatment, waste management, and transportation.

If looking at the well-being of the environment as a whole, then also the well-being of other species must be considered.

If should also be noted that the amount of resources are not necessarily fixed and their division is not necessarily a zero-sum game. For example, the worldwide production of food has steadily increased faster than population growth.

Overpopulation is also related to issues of birth control, with some nations like China using strict measures in order to reduce birth rates, while religious and ideological opposition to birth control has been cited as a factor contributing to overpopulation and poverty.

Malthus' theory

Main article: Malthusian catastrophe

In An Essay on the Principle of Population (first published in 1798), Thomas Malthus proposed that while resources tend to grow linearly, population grows exponentially. He argued 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, and estimated that this would occur by the middle of the 19th century. To avoid this happening, Malthus argued for population control through "moral restraint". His specific predictions failed because he used a static analysis, and extrapolated his numbers into the future without considering factors that could increase the resource base available to humanity (for example, the Green Revolution).

On a global scale, thusfar food production has grown faster than human populations. It has been argued that other changes impacting earth's ability to function as a suitable habitat for human beings, such as global warming, are indicative of population growth, and while temporarily sustainable, may ultimately lead to a decrease in the carrying capacity of the Earth. Among the best-known modern examples of such arguments is The Limits to Growth, a report produced for the Club of Rome in the early 1970s, and The Population Bomb, from the same era. Similarly, in his recent book Collapse (2005), Jared Diamond argues that human population growth is presently occurring at the expense of natural capital. Other examples of these arguments can also be found here.

Population as a function of food availability

Some recent research and experiments question the contemporary belief that human populations are a naturally explosive independent variable. Thinkers such as David Pimentel, a professor from Cornell University, Virginia Abernethy, Alan Thornhill, Russell Hopffenberg and author Daniel Quinn propose that like any 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 placing more land under agriculture.

Critics of this idea point out that birth rates are lowest in a developed country, which also has the highest access to food. In fact, some developed countries have both a diminishing population and an abundant food supply. The United Nations projects that the population of 51 countries or areas, including Germany, Italy, Japan and most of the successor states of the former Soviet Union, is expected to be lower in 2050 than in 2005.[2] This shows that human populations do not always grow to match the available food supply; many of these countries are major exporters of food.

Growth in food production has been greater than population growth. Food per person increased during the 1961-2005 period.

Food supplies are distributed very unevenly; rich nations have an abundance of food, while many poor nations suffer chronic famines. Desertification can cause loss of arable land.

The demographic transition

Main article: Demographic transition

The theory of demographic transition, while unproven to apply to all world regions, holds that within a generation after the standard of living and life expectancy increases, family sizes start dropping. Factors cited in the decline of birth rates include such social factors as 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 factor 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 dropoff in birth rates worldwide in all industrializing regions.

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 clearly having a birth dearth. Western Europe also is below replacement fertility levels. 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 female. 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.

Another version of demographic transition is that of Virginia Abernethy in Population Politics, in which she claims that the demographic transition is primarily in effect for nations where women enjoy a special status (see Fertility-opportunity theory). 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, and therefore not from a lack of reproductive rights.

"Demographic entrapment" is a concept developed by Maurice King that has not gained widespread acceptance. King argues that that this occurs when a country has a population larger than its carrying capacity, no possibiity of migration, and exports to little to be able to import food. This will cause starvation. He claims that for example many sub-Saharan nations are or will become stuck in demographic entrapment, instead of having a demographic transition.

For the world as a whole, number of children born per women decreased from 5.02 to 2.65 between 1950 and 2005. Europe 2.66 to 1.41. North America 3.47 to 1.99. Oceania 3.87 to 2.30. Central America 6.38 to 2.66. South America 5.75 to 2.51. Asia (excluding Middle East) 5.85 to 2.43. Middle East & North Africa 6.99 to 3.37. Sub-Saharan Africa 6.7 to 5.53. In 2050, the projected number of children born per women is 2.05. Only the Middle East & North Africa (2.09) and Sub-Saharan Africa (2.61) will then have numbers greater than 2.[3]

Some fear that a lack of access to birth control methods due to ideological and religous opposition may prevent a decline in birth rates and poverty.

Viewpoints on population growth

Many groups (for example, the World Wide Fund for Nature[4]) have argued that the carrying capacity for the human population has been exceeded. The United Nations indicates that about 850 million people are malnourished or starving, and 1.1 billion people do not have access to safe drinking water. Thus some argue that the Earth may support 6 billion people, but only on the condition that many live in misery. Optimists respond that worldwide poverty is declining. The percentage of the world's population living on less than $1 per day has halved in twenty years.[5]

Optimists believe that the 2006 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, Bjørn Lomborg argues that, because of the falling rate of population growth in most parts of the world and because of new science and technologies, there is little problem with overpopulation. A three-person rebuttal disagrees..

Optimists may also point out that meat production is very energy inefficient, so that food availability would increase if protein sources like soybeans were used in lieu of meat, since humans would then be eating lower on the food chain. However, given that this would require enough people giving up meat for soy and other plant based protein to make an agricultural shift in production meaningful, this argument may be unrealistic. It also assumes that the grain fed to livestock is fit for human consumption. [6].

Optimists claim that there will be no mass starvation due to a shortage of arable land. 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 (itself a scarce resource) limits 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.

Some claim that not all arable land will remain productive if used for agriculture, as they argue that some marginal land can only be made to produce food by unsustainable practices like slash-and-burn agriculture. Even with the modern techniques of agriculture, the sustainability of production is in question. One measure of the world's current overpopulation is established by The World Wildlife Fund and Global Footprint Network [7], which calculated for the year 2003, humanity's ecological footprint was 25 percent larger than the planet’s capacity to produce these resources. For the year 2050 the group calculates the footprint will be 100 percent larger. [8]. This analysis implies that the planet Earth is overpopulated by approximately 30 percent as of 2006.

Optimists have also been criticized for failing to account for future shortages in fossil fuels, currently used for fertilizer and transportation for modern agriculture. (See Hubbert peak and Future energy development.) They counter that there will be enough fossil fuels until suitable replacement technologies have been developed, for example hydrogen in a hydrogen economy.[9][10]

There are a variety of viewpoints as to when the Earth's carrying capacity was exceeded. According to the World Wide Fund for Nature, the date was 1986.[11]

Population and environment

An important, but sometimes neglected, factor to consider in any discussion of population is the role of nature and wildlife. Simply because there may be enough natural resources to maximize human numbers should not, many assert, be the sole consideration in doing so and any equation that leaves out other species is grossly narrow-minded and shortsighted. For one thing, they say, there is the fact that humankind has an aesthetic need and love for vast open spaces and an innate love for wild animals. For another there is an actual need to preserve nature if only for our own benefit. Trees, for example, provide oxygen and we all need to breathe. Yet another reason is simply the right of other species to exist and live their lives as they evolved to do. Says environmental author Jeremy Rifkin, "our burgeoning population and urban way of life have been purchased at the expense of vast ecosystems and habitats.... It's no accident that as we celebrate the urbanization of the world, we are quickly approaching another historic watershed: the disappearance of the wild."

Says Peter Raven former President of AAAS or the American Association for the Advancement of Science in their seminal work AAAS Atlas of Population & Environment, "Where do we stand in our efforts to achieve a sustainable world? Clearly, the past half century has been a traumatic one, as the collective impact of human numbers, affluence (consumption per individual) and our choices of technology continue to exploit rapidly an increasing proportion of the world's resources at an unsustainable rate.... During a remarkably short period of time, we have lost a quarter of the world's topsoil and a fifth of its agricultural land, altered the composition of the atmosphere profoundly, and destroyed a major proportion of our forests and other natural habitats without replacing them. Worst of all, we have driven the rate of biological extinction, the permanent loss of species, up several hundred times beyond its historical levels, and are threatened with the loss of a majority of all species by the end of the 21st century".

Overpopulation by world region

Overpopulation is clearer to visualise by individual regions of the world, where causes and effects are simpler to identify than using a world summary; while there are dozens of presently overpopulated world regions, the following examples are representative:

Peten region of Guatemala

This region is inhabitated by mostly indigenous peoples. The resource base is stretched thin by deforestation and inability of the fragile tropical forest soils to provide high yield agriculture. Decades of non-sustainable agriculture including considerable slash-and-burn activity by native peoples have left the region unable to feed or support the present population (in terms of food, drinking water, sanitation and other factors).

Arizona

There are numerous areas of the world that exhibit wealth and large land area. Paul Ehrlich suggested decades ago that certain USA areas including the state of Arizona, USA, do not have the water resources and or the extent of arable land to support the existing population.

Madagascar

Massive deforestation with resulting desertification, water resource degradation and soil loss has affected approximately ninety percent of Madagascar's previously biologically productive lands. Most of this loss has occurred since independence from the French, and is the result of local people trying merely to subsist. The country is currently unable to provide adequate food, fresh water and sanitation for its population.

India

India also has enormous problems with overpopulation. The current population is over a billion but India doesn't have the large land mass that China has. India is experiencing major problems with declining water tables due to over-extraction beyond sustainable yield.

Population projections

The world's human population has quadrupled in the course of the last hundred years.

The United Nations states that:

• Almost all growth will take place in the less developed regions, where today’s 5.3 billion population of underdeveloped countries is expected to swell to 7.8 billion in 2050. By contrast, the population of the more developed regions will remain mostly unchanged, at 1.2 billion.
• Worldwide population is currently growing by more than 75 million people per year. Net growth by mid-century is predicted by the United Nations to be 34 million per year in contrast to the roughly 76 million per year that was seen from 2000 to 2005.
• In 2000-2005, fertility at the world level stood at 2.65 children per woman, about half the level it had in 1950-1955 (5 children per woman). In the medium variant, global fertility is projected to decline further to 2.05 children per woman.
• During 2005-2050, nine countries are expected to account for half of the world’s projected population increase: India, Pakistan, Nigeria, Democratic Republic of the Congo, Bangladesh, Uganda, United States of America, Ethiopia, and China, listed according to the size of their contribution to population growth.
• Global life expectancy at birth, which is estimated to have risen from 46 years in 1950-1955 to 65 years in 2000-2005, is expected to keep on rising to reach 75 years in 2045-2050. In the more developed regions, the projected increase is from 75 years today to 82 years by mid-century. Among the least developed countries, where life expectancy today is just under 50 years, it is expected to be 66 years in 2045-2050.
• The population of 51 countries or areas, including Germany, Italy, Japan and most of the successor States of the former Soviet Union, is expected to be lower in 2050 than in 2005.
• During 2005-2050, the net number of international migrants to more developed regions is projected to be 98 million. Because deaths are projected to exceed births in the more developed regions by 73 million during 2005-2050, population growth in those regions will largely be due to international migration.
• In 2000-2005, net migration in 28 countries either prevented population decline or doubled at least the contribution of natural increase (births minus deaths) to population growth. These countries include Austria, Canada, Croatia, Denmark, Germany, Italy, Portugal, Qatar, Singapore, Spain, Sweden, United Arab Emirates and United Kingdom.[12]

United Nation's medium variant population projections by location.

Another United Nations report projects that world population will peak at 9.2 billion around 2075 [13].[14] Birth rates are now falling in most developing countries, while the actual populations in many developed countries would fall without immigration.[15]

The already mentioned David Pimentel claims 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 difficult lives with limited resources and widespread famine). [16]

The book The Little Green Handbook reasons that in 2050 about 7.7 billion people would be expected to suffer from illness, lack of adequate sanitation, hunger, and extreme poverty, provided that the high population estimates of year 2050 are realised.

Some countries currently have growth rates of over four percent. By 2050, it is estimated that

• Pakistan’s population will rise substantially, from 142 million to 318 million [17]
• India will displace China from first place with a population of about 1,550,000,000 [18]

Effects of overpopulation

Some problems associated with or exacerbated by human overpopulation:

• Inadequate fresh water for drinking water use as well as sewage treatment and effluent discharge
• Depletion of natural resources, especially fossil fuels
• Increased levels of air pollution, water pollution, soil contamination and noise pollution
• Deforestation and loss of ecosystems that sustain global atmospheric oxygen and carbon dioxide balance; about eight million hectares of forest are lost each year[19]
• Changes in atmospheric composition and consequent global warming
• Irreversible loss of arable land and increases in desertification
• Mass species extinctions. from reduced habitat in tropical forests due to slash-and-burn techniques that sometimes are practiced by shifting cultivators, especially in countries with rapidly expanding rural populations; present extinction rates may be as high as 140,000 species lost per year.
• High infant and child mortality
• Increased incidence of hemorrhagic fevers, HIV and other infectious diseases from crowding, disturbance of ecological systems and scarcity of available medical resources
• Starvation, malnutrition or poor diet with ill health and diet-deficiency diseases (e.g. rickets)
• Poverty coupled with inflation in some regions and a resulting low level of capital formation
• Low birth weight due to the inability of mothers to get enough resources to sustain a baby from fertilization to birth
• Low life expectancy in countries with fastest growing populations
• Unhygienic living conditions for many based upon water resource depletion, discharge of raw sewage and solid waste disposal
• High rate of unemployment in urban areas (leading to social problems)
• Elevated crime rate due to drug cartels and increased theft by people stealing resources to survive
• Conflict over scarce resources and crowding, leading to increased levels of warfare
• Over-utilization of infrastructure, such as mass transit, highways, and public health systems
• Higher land prices

Extraterrestrial population projections

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, by 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. Space advocates and others have made various projections regarding future human population growth in outer space. Marshall Savage (1992, 1994) has projected a population of five quintillion throughout the solar system by 3000, with the majority in the asteroid belt. Inhabitants of the asteroid belt may risk disaster caused by their home world colliding with other asteroids. Arthur C. 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. In Mining the Sky, John S. Lewis suggests that the staggering resources of the solar system could support 10 quadrillion (10^15) people.

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

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 regard as absurd.

Overpopulation as a theme in fiction

In 1729, Jonathan 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 - cannibalism, particularly the raising 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. The 1969 Star Trek: The Original Series episode entitled The Mark of Gideon dealt with a race of overpopulated aliens who abducted Captain Kirk to solve their population problem.

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 meters 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.

One of the reasons for this may be the rise of environmental fiction with The End of Nature (1990) by Bill McKibben, the environmental trilogy Ishmael (1992), The Story of B (1996), and My Ishmael (1997) by Daniel Quinn. With the host of environmental problems caused by overpopulation, almost by definition, talking about one is talking about the other.

Further Reading

• Virginia Abernethy, professor (emerita) of psychiatry and anthropology, Population Politics, (1993)
• Albert Bartlett, emeritus professor of physics, Arithmetic, Population, and Energy: The Forgotten Fundamentals of the Energy Crisis, (1978)
• Joel E. Cohen, Chair, Laboratory of Populations at the Rockefeller University, How Many People Can the Earth Support? (1996)
• Barry Commoner, American biologist and college professor Making Peace with the Planet (1990)
• Herman Daly, professor at the School of Public Policy at the University of Maryland, College Park Ecological Economics and the Ecology of Economics (1999)
• Paul R. Ehrlich, Bing Professor of Population Studies, The Population Bomb, (1968) The Population Explosion, (1990) The Population Bomb, (1995) reprint
• Garrett Hardin, 1941 Stanford University - Ph.D. Microbiology, Living Within Limits, (1995) reprint
• Bjørn Lomborg, Masters in political science at the University of Aarhus in 1991, The Skeptical Environmentalist: Measuring the Real State of the World, (2001)
• Andrew Mason, Professor, head of the University of Hawaii's population studies program, Population change and economic development in East Asia: Challenges met, opportunities seized (2001)
• Donella Meadows, lead author Ph.D. in biophysics from Harvard, Jorgen Randers, professor of policy analysis at the Norwegian School of Management, Dennis Meadows, director of the Institute for Policy and Social Science Research Limits to Growth: The 30-Year Update (Paperback) (2004)
• Thomas Malthus, English demographer and political economist, An Essay on the Principle of Population, (1798)
• Julian Lincoln Simon, professor of Business Administration The Ultimate Resource 2, (1998)"
• Ben J. Wattenberg, senior fellow at the neoconservative American Enterprise Institute, The Birth Dearth (1989) ??? Fewer: How the New Demography of Depopulation Will Shape Our Future, (2005)

See also

• Carrying capacity
• Ecological footprint
• Immigration reduction
• National Security Study Memorandum 200 (a U.S. NSS document from the 1970s)
• Over-consumption
• Population ageing
• Population biology
• Population control
• Population decline
• Population density
• Population ecology
• Population ethics
• Population growth
• Population pyramid
• Rientrodolce (an Italian interest group which lobbies against overpopulation)
• Sustainability
• Tragedy of the commons
• Urban sprawl
• Water crisis
• World Population Foundation

External links

• World Population Clock
• AAAS Atlas of Population and Environment
• U.S. Population Reaches 300 Million, Heading for 400 Million -- No Cause for Celebration
• Earth Policy Institute Resources on POPULATION and HEALTH
• VOA News - World Population Growth to be Concentrated in Developing Nations
• Map over population density
• Population Research Institute
• Population-Environment Balance (organization)
• Ecofuture.org Population and Sustainability Website
• A Crusade Against Overpopulation
• Is World Population a Concern? Robert Heilbroner, Thomas Malthus, and the Application of Both
• Overpopulation and Happiness
• newadvent - overpopulation
• Negative Population Growth (organization)
• Overpopulation.com: Overpopulation FAQ
• Planned Parenthood mission and population stance
• Sustainable Population Australia
• Population Action International (organization)
• DieOff.org, human population crash website
• Population Connection (formerly Zero Population Growth; organization)
• Appeal to Marco Pannella on overpopulation
• Humanity has no enemies apart from itself (English and Lithuanian)
• Sierra Club's Population Campaign (organization)
• SUSPS (concerned with the Sierra Club's immigration policy; organization)
• Voluntary Human Extinction Movement
• World population projections by the United Nations "World Population to 2300"
• AAAS Atlas of Population and Environment

• World Population Balance (organization)
• Article about overpopulation
• Introduction to Social Macrodynamics
• Be In The Know: Six Billion and Counting, Full Effect
• MOBUTOBE by art group monochrom. A satirical art activism initiative for the "accomplishment of total population".
• Population and the Environment: The Global Challenge
• World Scientists' Warning to Humanity