Overpopulation refers to a condition where an organism's numbers exceed the carrying capacity of its habitat. In common parlance, the term usually refers to the relationship between the human population and its environment, the earth.
Overpopulation is not a function of the size or density of the population. Overpopulation is determined using the ratio of population to available sustainable resources. If a given environment has a population of ten, but there is food or drinking water enough for only nine, then that environment is overpopulated; if the population is 100 individuals but there is enough food, shelter, and water for 200 for the indefinite future, then it is not. Overpopulation can result from an increase in births, a decline in mortality rates due to medical advances, from an increase in immigration, a decrease in emigration, or from an unsustainable biome and depletion of resources. It is possible for very sparsely-populated areas to be overpopulated, as the area in question may have a very meager or non-existent capability to sustain human life (e.g. the middle of the Sahara desert or Antarctica).
The resources to be considered when evaluating whether an ecological niche is overpopulated include clean water, clean air, food, shelter, warmth, and other resources necessary to sustain life. If the quality of human life is addressed as well, there are then additional resources to be considered, such as medical care, employment, money, education, fuel, electricity, proper sewage treatment, waste.
Some countries have managed to substantially increase their carrying capacity by using technologies such as modern agriculture, desalination, and nuclear power. Some economists, such as Thomas Sowell and Walter E. Williams have argued that poverty and famine are caused by bad government and bad economic policies, and not by overpopulation. In his book The Ultimate Resource, economist Julian Simon argued that higher population density leads to more specialization and technological innovation, and that this leads to a higher standard of living. Simon also claimed that if you look at a list of countries ranked in order by population density, there is no correlation between population density, and poverty and famine, and instead, if you look at a list of countries ranked in order by government corruption, there is a huge correlation between government corruption, and poverty and famine.
Others argue that overpopulation is an important cause of these problems. Scientists report that nature might have, thus, started its own solution by spreading infertility amongst humans through viruses (such as Adeno-associated virus) that are otherwise unharmful and believe that technology cannot adress the problems and that population should be reduced
On a global scale, since the industrial revolution, food production has sometimes grown faster than human population. However, it has been argued that other changes impacting Earth's ability to function as a suitable habitat for human beings, such as global warming, desertification, overfishing, peak oil, soil degradation, deforestation, aquifer depletion and other environmental problems caused by industrialization, will significantly reduce food production or factors necessary for well-being. Given recent population growth, this may cause a Malthusian catastrophe.
In a short science fiction story published in 1969 called "Eco-catastrophe" reprinted from "Ramparts" Magazine, Paul Ehrlich wrote "the population of the U.S. will shrink from 250 million to about 22.5 million before 1999 because of famine and global warming", though it should be noted that between 1950 and 1984, as the Green Revolution transformed agriculture around the globe, world grain production increased by 250%, Ehrlich also predicted, "Before 1985, mankind will enter a genuine age of scarcity . . . in which the accessible supplies of many key minerals will be facing depletion." According to The Skeptical Environmentalist by Bjørn Lomborg, Ehrlich's "predictions" did not materialise. (See Erlich's answer to his critics and The Ultimate Resource, by Julian Simon, which challenges Ehrlich's ideas.) However Simon himself once stated "We now have in our hands in our libraries, really the technology to feed, clothe, and supply energy to an ever-growing population for the next 7 billion years... We [are] able to go on increasing forever" (Myers and Simon, 1994, 65). These comments have subjected Simon himself to criticism.
In Facing the Limits to Growth the authors of the 1972 study Limits to Growth tell of the difficulty in getting the idea of the necessity of limiting human population growth past "Entrenched political, economic, and religious cliques." And they acknowledge that revision has been necessary, "Because of the long time horizon involved in our studies, we always realized it would require several decades to get any perspective on the accuracy of our forecasts", however, "the basic conclusions are still the same. We have modified our model only a little to reflect some better data about the effects of technology on land yields and birth rates.
Between 1950 and 1984, as the Green Revolution transformed agriculture around the globe, world grain production increased by 250%. However, agricultural productivity has declined in many world regions in the past ten to 20 years due to overdrafting of groundwater (such as has occurred on the North Plain of China) , overgrazing, extensive slash-and-burn and resulting soil exhaustion and erosion. The energy for the Green Revolution was provided by fossil fuels in the form of fertilizers (natural gas), pesticides (oil), and hydrocarbon fueled irrigation. David Pimentel, professor of ecology and agriculture at Cornell University, and Mario Giampietro, senior researcher at the National Research Institute on Food and Nutrition (INRAN), place in their study Food, Land, Population and the U.S. Economy the maximum U.S. population for a sustainable economy at 200 million. To achieve a sustainable economy and avert disaster, the United States must reduce its population by at least one-third, and world population will have to be reduced by two-thirds, says the study. The authors of this study believe that the mentioned agricultural crisis will only begin to impact us after 2020, and will not become critical until 2050.
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).
The oncoming peaking of global oil production (and subsequent decline of production), along with the peak of North American natural gas production may precipitate this agricultural crisis much sooner than expected. Geologist Dale Allen Pfeiffer claims that coming decades could see spiraling food prices without relief and massive starvation on a global level such as never experienced before.
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.
In his recent book Collapse (2005), Jared Diamond argues that many earlier civilizations have collapsed due to environmental problems, and warns of current environmental problems. For example, he argues that it was overpopulation that led the now recovering inhabitants of Easter Island (a.k.a. Rapa Nui) to destroy their once beautiful island paradise.
From circa AD 1000 to circa 1650/1700 AD, Rapa Nui's population increased significantly. Some estimate the population reached a high of 10,000 or even 15,000. Moai carving and transport were in full swing from 1400 to 1650, less than 100 years before the first recorded European visitors to the island. By the late nineteenth century the population had fallen to a low of 132. Deforestation, civil wars, European diseases and slave raiding all contributed to the population crash. Core sampling and archaeology from the island has revealed a slice of Rapa Nui history that speaks of deforestation, extinction of native bird populations, soil depletion, and erosion as well as loss of access to deep sea fish as wood became scarce. From this devastating ecological scenario it is not hard to imagine the resulting overpopulation, food shortages, and ultimate collapse of Rapa Nui society. Evidence of cannibalism at that time is present on the island, though very scant. Van Tilburg cautiously asserts, "The archaeological evidence for cannibalism is present on a few sites.However, he also notes situations in which humans have managed their natural resources well.
For reasons that are still debated, the Maya centers of the southern lowlands went into decline during the 8th and 9th centuries and were abandoned shortly thereafter. There is evidence that the Maya population exceeded carrying capacity of the environment including exhaustion of agricultural potential and overhunting of megafauna.
Julian Simon argued that any poor country that chose to adopt property rights would become wealthy, enabling science, technology, industrialization, modern agriculture, hydroponic farming, nuclear power, and desalination, thereby enabling a rich, first world standard of living, even if the Earth had tens of billions of people.
In his 2007 book The Improving State of the World, Indur M. Goklany argues that there is little problem with overpopulation, as humanity's state is rapidly improving overall and environmental problems can be overcome. He proposes that in the early stages of economic and technological development, negative environmental impacts increase because securing access to such necessities as food, shelter, and energy is seen as more important than protecting the environment. As development continues and these supply problems are solved, environmental impact becomes a higher priority, and steps are then taken to reduce it. This pattern can be seen for many environmental indicators, such as air quality, availability of safe water, sanitation, and toxic residues (e.g., DDT and PCBs) in human tissues, which initially declined with increasing development but have more recently improved.
James Surowiecki argues in his review of the book that "The reality ... is that the fight over environmental regulation, at least in the United States, was -- and remains -- a fierce one and that environmental skeptics and businesses have done their best to prevent regulations such as the Clean Air and Clean Water Acts from ever becoming law. It is also the case that without those regulations, the 'cleaner planet' Goklany sees today would not exist.... The point is that far from being the inevitable product of a strong economy, environmental improvement is often the result of political struggles that could very easily have gone the other way." Goklansy in a reply stated "I am no more convinced than he is about the inevitability of progress" and that the book had stated "a democratic society, because it has the political means to do so, will translate its desire for a cleaner environment into laws, either because cleanup is not voluntary or rapid enough, or because of sheer symbolism. The wealthier such a society, the more affordable -- and more demanding -- its laws."
The theory of demographic transition, while unproven to apply to all world regions, holds that widespread empirical evidence shows that 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.
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. Of course, many countries still have high population growth rates while having lower Total Fertility Rates. This is because high population growth in the past has skewed the age demographic in many countries toward a young age, meaning that the population will still rise as the more numerous younger generation approaches maturity.
"Demographic entrapment" is a concept developed by Maurice King that has not gained widespread acceptance. King argues that this occurs when a country has a population larger than its carrying capacity, no possibility of migration, and exports too 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, the number of children born per woman decreased from 5.02 to 2.65 between 1950 and 2005. A breakdown by continent is as follows:
In 2050, the projected world number of children born per woman is 2.05. Only the Middle East & North Africa (2.09) and Sub-Saharan Africa (2.61) will then have numbers greater than 2.05.
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.
There are an estimated 350 million women in the poorest countries of the world who either did not want their last child, do not want another child or want to space their pregnancies, but they lack access to information, affordable means and services to determine the size and spacing of their families. In the developing world, some 514,000 women die of complications from pregnancy and abortion on a yearly basis. Additionally, 8 million infants die, many because of malnutrition or preventable diseases.
In the United States, in 2001, almost half of pregnancies were unintended.
As of June 2008, Egyptian Minister of Health and Population Hatem el-Gabali announced that his country has set aside 480 million Egyptian pounds (about 90 million U.S. dollars) to cope with its overpopulation problem through family planning.
These reflect the comments also of the United States Geological Survey in their paper The Future of Planet Earth: Scientific Challenges in the Coming Century "As the global population continues to grow...people will place greater and greater demands on the resources of our planet, including mineral and energy resources, open space, water, and plant and animal resources." "Earth's natural wealth: an audit" by New Scientist magazine states that many of the minerals that we use for a variety of products are in danger of running out in the near future. "A handful of geologists around the world have calculated the costs of new technologies in terms of the materials they use and the implications of their spreading to the developing world. All agree that the planet's booming population and rising standards of living are set to put unprecedented demands on the materials that only Earth itself can provide. Limitations on how much of these materials is available could even mean that some technologies are not worth pursuing long term.... "Virgin stocks of several metals appear inadequate to sustain the modern 'developed world' quality of life for all of Earth's people under contemporary technology" .
On the other hand, some writers, such as Julian Simon, Bjorn Lomborg and others of a libertarian persuasion believe that resources abound for a furtherance of population growth. Population scientists have agreed with their assessments that there are indeed more resources left that would enable continued population growth. However, they warn, this will be at a high cost to the Earth - and thus to us, "the technological optimists are probably correct in claiming that overall world food production can be increased substantially over the next few decades...[however] the environmental cost of what Paul R. and Anne H. Ehrlich describe as 'turning the Earth into a giant human feedlot' could be severe. A large expansion of agriculture to provide growing populations with improved diets is likely to lead to further deforestation, loss of species, soil erosion, and pollution from pesticides and fertilizer runoff as farming intensifies and new land is brought into production. Since we are intimately dependent upon the living systems of the Earth, scientists have questioned the wisdom of further expansion.
According to the Millennium Ecosystem Assessment, a four-year research effort by 1,360 of the world’s leading scientists commissioned to measure the actual value of natural resources to humans and the world, "The structure of the world’s ecosystems changed more rapidly in the second half of the twentieth century than at any time in recorded human history, and virtually all of Earth’s ecosystems have now been significantly transformed through human actions. "Ecosystem services, particularly food production, timber and fisheries, are important for employment and economic activity. Intensive use of ecosystems often produces the greatest short-term advantage, but excessive and unsustainable use can lead to losses in the long term. A country could cut its forests and deplete its fisheries, and this would show only as a positive gain to GDP, despite the loss of capital assets. If the full economic value of ecosystems were taken into account in decision-making, their degradation could be significantly slowed down or even reversed." The MA blames habitat loss and fragmentation for the continuing disappearance of species.
Another study by the United Nations Environment Programme (UNEP) called the Global Environment Outlook which involved 1,400 scientists and took five years to prepare comes to similar conclusions. It "found that human consumption had far outstripped available resources. Each person on Earth now requires a third more land to supply his or her needs than the planet can supply." It faults a failure to "respond to or recognise the magnitude of the challenges facing the people and the environment of the planet... 'The systematic destruction of the Earth's natural and nature-based resources has reached a point where the economic viability of economies is being challenged - and where the bill we hand to our children may prove impossible to pay'... The report's authors say its objective is 'not to present a dark and gloomy scenario, but an urgent call to action'. It warns that tackling the problems may affect the vested interests of powerful groups, and that the environment must be moved to the core of decision-making... '
Additionally, other issues involving quality of life - would most people want to live in a world of billions more people - and the basic right of other species to exist in their native environments come into play.
However, the amount of freshwater is not necessarily limited to what is currently available in nature. Malta derives two thirds of its freshwater from desalination of salt water. This is an energy-intensive process. One possible solution is large expansion of nuclear powered desalination plants. Such plants already exist. Some argue that there are billions of years of nuclear fuel available. Critics point to the high costs of desalination technologies, especially for poor third world countries, the impracticability and cost of transporting or piping massive amounts of desalinated seawater throughout the interiors of large countries, and the "lethal byproduct of saline brine that is a major cause of marine pollution when dumped back into the oceans at high temperatures.
One study of the costs of desalination and its transport says that "Indeed, one needs to lift the water by 2000 m, or transport it over more than 1600 km to get transport costs equal to the desalination costs.. Desalinated water is expensive in places that are both somewhat far from the sea and somewhat high, such as Riyadh and Harare. In other places, the dominant cost is desalination, not transport. This leads to relatively low costs in places like Beijing, Bangkok, Zaragoza, Phoenix, and, of course, coastal cities like Tripoli." Still, the study, while generally positive about the technology for affluent areas that are proximate to oceans, concludes that "Desalinated water may be a solution for some water-stress regions, but not for places that are poor, deep in the interior of a continent, or at high elevation. Unfortunately, that includes some of the places with biggest water problems.
Israel is now desalinating water for a cost of 53 cents per cubic meter. Singapore is desalinating water at a cost of 49 cents per cubic meter. In the United States, the cost of desalination is $3.06 for 1,000 gallons (81 cents per cubic meter).
The world's largest desalination plant is the Jebel Ali Desalination Plant (Phase 2) in the United Arab Emirates, which is capable of producing 300 million cubic meters of water per year, or about 2500 gallons of water per second. The largest desalination plant in the United States is the one at Tampa Bay, Florida, which began desalinizing 25 million gallons (95000 m³) of water per day in December 2007. A January 17, 2008, article in the Wall Street Journal states, "World-wide, 13,080 desalination plants produce more than 12 billion gallons of water a day, according to the International Desalination Association." After being desalinized at Jubail, Saudi Arabia, water is pumped inland though a pipeline to the capital city of Riyadh.
More than 100 countries now import wheat. Some 40 countries import rice. Egypt and Iran rely on imports for 40% of their grain supply. Algeria, Japan, South Korea and Taiwan import 70% or more. Yemen and Israel import more than 90%. And just 6 countries - the US, Canada, France, Australia, Argentina and Thailand - supply 90% of grain exports. The US alone controls almost half of world grain exports.
The amounts of natural resources in this context are not necessarily fixed, and their distribution is not necessarily a zero-sum game. For example, due to the Green Revolution and the fact that more and more land is appropriated each year from wild lands for agricultural purposes, the worldwide production of food has steadily increased faster than population growth. World food production per person was considerably higher in 2005 than 1961.
As world population doubled from 3 billion to 6 billion, daily calorie consumption in poor countries increased from 1,932 to 2,650, and the percentage of people in those countries who were malnourished fell from 45% to 18%. This suggests that Third World poverty and famine are caused by underdevelopment, not overpopulation. However, others question these statistics.
The number of people who are overweight has surpassed the number who are malnourished. In a 2006 news story, MSNBC reported, "There are an estimated 800 million undernourished people and more than a billion considered overweight worldwide.
The Food and Agriculture Organization of the United Nations states in its report The State of Food Insecurity in the World 2006, that while the number of undernourished people in the developing countries has declined by about three million, a smaller percentage of the populations of developing countries is undernourished today compared with 1990–92: 17 percent against 20 percent. Furthermore, FAO’s projections suggest that the proportion of hungry people in developing countries could be halved from 1990-92 levels to 10 percent by 2015. The FAO also states "We have emphasized first and foremost that reducing hunger is no longer a question of means in the hands of the global community. The world is richer today than it was ten years ago. There is more food available and still more could be produced without excessive upward pressure on prices. The knowledge and resources to reduce hunger are there. What is lacking is sufficient political will to mobilize those resources to the benefit of the hungry."
As of 2008, increased farming for use in biofuels, world oil prices at over $100 a barrel, global population growth, climate change, loss of agricultural land to residential and industrial development, and growing consumer demand in China and India have pushed up the price of grain. Food riots have recently taken place in many countries across the world. An epidemic of stem rust on wheat caused by race Ug99 is currently spreading across Africa and into Asia and is causing major concern. A virulent wheat disease could destroy most of the world’s main wheat crops, leaving millions to starve. The fungus has spread from Africa to Iran, and may already be in Afghanistan and Pakistan.
Hunger and malnutrition kill nearly 6 million children a year, and more people are malnourished in sub-Saharan Africa this decade than in the 1990s, according to a report released by the Food and Agriculture Organization. In sub-Saharan Africa, the number of malnourished people grew to 203.5 million people in 2000-02 from 170.4 million 10 years earlier says The State of Food Insecurity in the World report.
According to the BBC, the famine in Zimbabwe was caused by government seizure of farmland. However drought has also played a major role. Thirteen-million people are threatened by famine, in light of the drought in southern Africa. Six-million of them live in Zimbabwe. So that is a contingent of fully half of those potentially threatened by the current food shortages, if indeed they get worse, as is projected. Prior to this combination of drought and seizure of farmland, Zimbabwe had been exporting so much food that it was called "the breadbasket of southern Africa." So other countries were also harmed by these farm seizures. People who study the Zimbabwean famine claim that normally there are more than enough natural resources to feed the people. Some claim that the dams and rivers in Zimbabwe are full, and that the famine has nothing to do with drought. And though it's undoubtedly true that bad governance has exacerbated the famine, still notes the article, "Four weeks without rain at the critical germination phase has led to the failure of [the villagers] small crops. There will be no harvest again until next June."
Prior to President Robert Mugabe's seizure of the farmland in Zimbabwe, the farmers had been using irrigation to deal with drought, but during the seizures of the farmland, much of the irrigation equipment was either vandalized or looted. A 2006 BBC article about Mugabe's seizure of farmland states, "Critics say the reforms have devastated the economy and led to massive hunger. Much of the formerly white-owned land is no longer being productively used - either because the beneficiaries have no experience of farming or they lack finance and tools. Many farms were wrecked when they were invaded by government supporters.
Israel has 302 people per square kilometre compared with Zimbabwe's 33 people per square kilometre. Although Israel is a desert country with frequent drought and very high population density, it does not have famine. One possible reason why Israel does not have famine is because its government encourages farmers to use modern agriculture and irrigation to grow huge amounts of food. Still, Israel remains a net importer of food, somewhat detracting from this argument. It must also be noted that the high productivity of modern agriculture is currently dependent of the utilization of fossil fuels for pesticide and fuel.
Proponents of this theory argue that every time food production is increased, the population grows. Some human populations throughout history support this theory. Populations of hunter-gatherers fluctuate in accordance with the amount of available food. Population increased after the Neolithic Revolution and an increased food supply. This was followed by subsequent population growth after subsequent agricultural revolutions.
Critics of this idea point out that birth rates are lowest in the 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. The United Nations projects that the population of 51 countries or areas, including Germany, Italy, Japan and most of the states of the former Soviet Union, is expected to be lower in 2050 than in 2005. This shows that human populations do not always grow to match the available food supply; also, many of these countries are major exporters of food. Nevertheless, on the global scale the world population is increasing.
After China and India, there is a second tier of smaller countries with large water deficits — Algeria, Egypt, Iran, Mexico, and Pakistan. Four of these already import a large share of their grain. Only Pakistan remains self-sufficient. But with a population expanding by 4 million a year, it will also likely soon turn to the world market for grain.
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; however, many of the gains of agricultural technology are now historic, with new advances being more difficult to achieve. With new technologies, it is possible to grow crops on some marginal land under certain conditions. Aquaculture could theoretically 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.
Some scientists have said that in the future, densely populated cities will use vertical farming to grow food inside skyscrapers.
Some countries, such as the United Arab Emirates and particularly the Emirate of Dubai have constructed large artificial islands, or have created large dam and dike systems, like the Netherlands, which reclaim land from the water to increase their total land area.
The space taken by a human being itself is not a problem. It has been noted by a number of thinkers who deny that overpopulation is a problem - like noted philosopher Justin West - that the entire population of the world could live in Texas (or a land mass the size of Texas). Texas has a total surface area of , which is 7.30174326 × 10^12 square feet. Divided by 7 billion (slightly larger than the current population of the world) would yield an average of per person. Were everyone allotted space thusly, a family of 4 would have roughly a home. Compacted this way, the rest of North America, and all of South America, Europe, Asia, Africa, Australia and Antarctica would be left vacant of human beings and open to farming. This is assuming, of course, single floor houses, as well as no requirements for public spaces such as roads, schools, hospitals, separate commercial or industrial buildings, or recreational space. Also questionable is the meaning of "could live", with an average space between two people of just over 100 feet.
In his 1992 book Earth in the Balance, Al Gore wrote, "... it ought to be possible to establish a coordinated global program to accomplish the strategic goal of completely eliminating the internal combustion engine over, say, a twenty-five-year period... Plug in electric cars such as the Tesla Roadster suggest that Gore's prediction will come true. The Earth has enough uranium to provide humans with all of their electricity needs until the sun blows up in 5 billion years, assuming that we develop large scale breeder reactors.
There has also been increasing development in extracting renewable energy, such as from solar, wind, and tidal energy. If used on a wide scale, these could theoretically fulfill most, if not all, of the energy needs currently being filled by non-renewable resources. However, it should be noted that some of these renewable resources also have ecological footprints, though they may be different or smaller than some non-renewable resources. Terrestrial solar and wind power cannot be used for base load generation without some sort of energy storage or transmission over very large geographical areas, since they are transient sources of energy.
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. Others posit that poverty was worse in the past when the population was smaller, and that worldwide poverty is declining as the population grows. The percentage of the world's population living on less than $1 per day has halved in twenty years; these are inflation adjusted numbers. Furthermore, a 2007 article from Investor's Business Daily suggests that the population explosion has been accompanied by an increase in worldwide living standards. The article states, "On a per-person basis, real average incomes have more than tripled since 1950 worldwide. And in once-poor areas with the greatest trade liberalization — like East Asia — growth has been even greater, soaring 5,675% from 1950 to 2003..
However states the UN Human Development Report from 1997 "During the last 15-20 years, more than 100 developing countries, and several East European countries, have suffered from disastrous growth failures. The reductions in standard of living have been deeper and more long-lasting than what was seen in the industrialised countries during the depression in the 1930s. As a result, the income for more than one billion people has fallen below the level that was reached 10, 20 or 30 years ago." How do some massage the numbers to come up with a rosy picture for the third world? Says Pimm and Harvey "Lomborg’s great optimism about humanity’s future shows up in the way he presents statistics. In sub-Saharan Africa, 'starving people' constituted '38 percent in 1970 … [but only] '33 percent … in 1996. [The percentage is] expected to fall even further to 30 percent in 2010.' The absolute numbers of starving are curiously missing from these paragraphs. Roughly, the region’s population doubled between 1970 and 1996. To keep the numbers of starving constant, the percentage would have had to have dropped by more than half.". In other words, the percentages Lomborg presents would indeed be impressive in an environment with no population growth, but in one wherein the population has doubled the absolute numbers has actually risen dramatically.
For example, North Korea and South Korea have similar population densities, natural resources, and even parallel cultures (ethnically based in Korean) sharing the same peninsular homeland; but, whereas North Korea is a poverty-stricken, socialist country where its people are suffering from terrible famine and are destitute, South Korea is a prosperous, capitalist country where the people are well nourished and materially/economically secure (without just a small portion of the entire poulation benefiting from the wealth [as do North Korea's Communist Party officials with the little wealth their country has] but all the nation's people benefitting from their economic successes) despite the fact that South Korea's population is double that of North Korea's population with a higher fertility rate (hence a faster growing population) as well. This suggests that it is bad economic polices, not "overpopulation," that causes famine. Various Indices of Economic Freedom suggest that countries with a strong level of economic freedom never have famines or even food shortages, regardless of how high their population densities. However, it must be taken into account that most prosperous capitalist countries, with high population densities, are extremely reliant on imports from poorer countries and therefore have not solved the problem of massive poverty, but are assuming a different position in it. Affluent capitalist countries may exceed their own land bases' carrying capacity and rely on poorer countries for resources, production, and labor in order to maintain their level of wealth. It is not the case that affluent countries are affected as negatively by overpopulation as are poorer countries. But, the problem of poverty and overpopulation must be looked at on a global basis and not country by country, as certain countries may very well benefit from the abundance of cheap labor in another country.
Says Peter Raven, former President of AAAS (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."
The increase will be most dramatic in the poorest and least-urbanised continents, Asia and Africa. Surveys and projections indicate that all urban growth over the next 25 years will be in developing countries. One billion people, one-sixth of the world's population, or one-third of urban population, now live in shanty towns, which are seen as "breeding grounds" for social problems such as crime, drug addiction, alcoholism, poverty and unemployment. In many poor countries slums exhibit high rates of disease due to unsanitary conditions, malnutrition, and lack of basic health care.
In 2000, there were 18 megacities – conurbations such as Tokyo, Mexico City, Mumbai (Bombay), São Paulo and New York City – that have populations in excess of 10 million inhabitants. Greater Tokyo already has 35 million, more than the entire population of Canada.
By 2025, according to the Far Eastern Economic Review, Asia alone will have at least 10 hypercities, those with 20 million or more, including Jakarta (24.9 million people), Dhaka (25 million), Karachi (26.5 million), Shanghai (27 million) and Mumbai (with a staggering 33 million). Lagos has grown from 300,000 in 1950 to an estimated 15 million today, and the Nigerian government estimates that city will have expanded to 25 million residents by 2015. Chinese experts forecast that Chinese cities will contain 800 million people by 2020.
Despite this increase in population density within the cities and the rise of more megacities, UN Habitat stated in its reports that if these 2 matters do not negate the fact that city living can be the best solution for dealing with the rising population numbers (and thus still be a good approach on dealing with overpopulation). This is because cities concentrate human activity into one place, making the environmental damage on other places smaller. Letting the cities have a positive influence however, can only be achieved if urban planning is improved and if the city services are properly maintained.
Regions are ranked by their per capita consumption of resources. However this ranking may be out-dated, since data was collected in 2003.
In the 1970s, Gerard O'Neill suggested building space habitats that could support 30,000 times the carrying capacity of Earth using just the asteroid belt and that the solar system as a whole could sustain current population growth rates for a thousand years. Marshall Savage (1992, 1994) has projected a population of five quintillion throughout the solar system by 3000, with the majority in the asteroid belt. Arthur C. Clarke, a fervent supporter of Savage, argued 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 (10^16) 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. However, Gerard O'Neill's calculations show that the Earth could offload all new population growth with a launch services industry about the same size as the current airline industry inO'Neill, Gerard K. (1981). 2081: A Hopeful View of the Human Future. Simon and Schuster. ISBN 0-671-44751-3..
In 2006, WWF's "Living Planet" report stated that if we all want to live with a high degree of luxury (European standards), we would be spending three times more than what the planet can supply. In other reports, such as the one cited in the The Planet-documentary, it is mentioned that we already consume five times more than that the planet can supply, given the current population numbers and our standard of living. Although there is still no real consensus, it is expected that the amount of overpopulation currently lies within this range.
Steve Jones, head of the biology department at University College London, has said, "Humans are 10,000 times more common than we should be, according to the rules of the animal kingdom, and we have agriculture to thank for that. Without farming, the world population would probably have reached half a million by now."
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 Harry Harrison's Make Room! Make Room! also became a powerful film (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. Another 1971 film, called The Last Child also took a stub at laws in the future where families are only allowed to have 1 child and people over 65 are forbidden medical care.
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 one trillion living in just 100,000 cities on Earth. In Warhammer 40,000, Hive Worlds are planets that literately exist to export population for colonization or military service, and people live in multi-kilometer tall cities called Hives which are essentially artificial mountains of geodesic domes and packed towers. Such worlds contain hundreds of billions or trillions of people living in miserable conditions, packed into ancient cities so vast the lower sections are actually forgotten and unmapped wilderness populated by savages.
A similar point, from the opposite point of view, is made by Ursula K. LeGuin in the utopian part of her novel Always Coming Home, in which the visiting anthropologist recognises that one of the reasons for the success and stability of the Kesh culture is simply that there are fewer of them (in the post-apocalyptic future) than previously.
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.
In the video Are We Smarter Than Yeast?, Dan Chay portrays the similarities between our civilisation and those of yeast in regards to overcrowding.