The term human overpopulation refers to the relationship between the entire human population and its environment: the Earth, or to smaller geographical areas such as countries. Overpopulation can result from an increase in births, a decline in mortality rates, an increase in immigration, or an unsustainable biome and depletion of resources. It is possible for very sparsely populated areas to be overpopulated if the area has a meagre or non-existent capability to sustain life (e.g. a desert). Advocates of population moderation cite issues like quality of life, carrying capacity, and risk of starvation as a basis to argue for population decline. Scientists suggest that the human impact on the environment as a result of overpopulation, profligate consumption and proliferation of technology has pushed the planet into a new geological epoch known as the Anthropocene.
Overview
Human population has been rising continuously since the end of the Black Death, around the year 1350, although the most significant increase has been since the 1950s, mainly due to medical advancements and increases in agricultural productivity. The rate of population growth has been declining since the 1980s, while the absolute total numbers are increasing. Recent rate increases in several countries previously enjoying steady declines are also apparently contributing to continued growth in total numbers. The United Nations has expressed concerns on continued population growth in sub-Saharan Africa. Recent research has demonstrated that those concerns are well grounded. As of September 29, 2018 the world's human population is estimated to be 7.654 billion. Or, 7,622,106,064 on May 14, 2018 and the United States Census Bureau calculates 7,472,985,269 for that same date. and over 7 billion by the United Nations. Most contemporary estimates for the carrying capacity of the Earth under existing conditions are between 4 billion and 16 billion. Depending on which estimate is used, human overpopulation may or may not have already occurred. Nevertheless, the rapid recent increase in human population is causing some concern. The population is expected to reach between 8 and 10.5 billion between the years 2040 and 2050. In 2017, the United Nations increased the medium variant projections to 9.8 billion for 2050 and 11.2 billion for 2100.
The recent rapid increase in human population over the past three centuries has raised concerns that the planet may not be able to sustain present or future numbers of inhabitants. The InterAcademy Panel Statement on Population Growth, circa 1994, stated that many environmental problems, such as rising levels of atmospheric carbon dioxide, global warming, and pollution, are aggravated by the population expansion. Other problems associated with overpopulation include the increased demand for resources such as fresh water and food, starvation and malnutrition, consumption of natural resources (such as fossil fuels) faster than the rate of regeneration, and a deterioration in living conditions. Wealthy but highly populated territories like Britain rely on food imports from overseas. This was severely felt during the World Wars when, despite food efficiency initiatives like "dig for victory" and food rationing, Britain needed to fight to secure import routes. However, many believe that waste and over-consumption, especially by wealthy nations, is putting more strain on the environment than overpopulation.
In spite of concerns about overpopulation, widespread in developed countries, the number of people living in extreme poverty globally shows a stable decline (this has been disputed by some experts), even though the population has grown seven-fold over the last 200 years. Child mortality has declined, which in turn has led to reduced birth rates, thus slowing overall population growth. The global number of famine-related deaths have declined, and food supply per person has increased with population growth.
Most countries have no direct policy of limiting their birth rates, but the rates have still fallen due to education about family planning and increasing access to birth control and contraception.
History of concern
Concern about overpopulation is an ancient topic. Tertullian was a resident of the city of Carthage in the second century CE, when the population of the world was about 190 million (only 3–4% of what it is today). He notably said: "What most frequently meets our view (and occasions complaint) is our teeming population. Our numbers are burdensome to the world, which can hardly support us.... In very deed, pestilence, and famine, and wars, and earthquakes have to be regarded as a remedy for nations, as the means of pruning the luxuriance of the human race." Before that, Plato, Aristotle and others broached the topic as well.
Throughout recorded history, population growth has usually been slow despite high birth rates, due to war, plagues and other diseases, and high infant mortality. During the 750 years before the Industrial Revolution, the world's population increased very slowly, remaining under 250 million.
By the beginning of the 19th century, the world population had grown to a billion individuals, and intellectuals such as Thomas Malthus predicted that humankind would outgrow its available resources, because a finite amount of land would be incapable of supporting a population with a limitless potential for increase. Mercantillists argued that a large population was a form of wealth, which made it possible to create bigger markets and armies.
During the 19th century, Malthus's work was often interpreted in a way that blamed the poor alone for their condition and helping them was said to worsen conditions in the long run. This resulted, for example, in the English poor laws of 1834 and in a hesitating response to the Irish Great Famine of 1845–52.
The UN publication 'World population prospects' (2017) projects that the world population will reach 9.8 billion in 2050 and 11.2 billion in 2100. Human population is predicted to stabilise soon thereafter.
A 2014 study published in Science challenges this projection, asserting that population growth will continue into the next century. Adrian Raftery, a University of Washington professor of statistics and sociology and one of the contributors to the study, says: "The consensus over the past 20 years or so was that world population, which is currently around 7 billion, would go up to 9 billion and level off or probably decline. We found there's a 70 percent probability the world population will not stabilize this century. Population, which had sort of fallen off the world's agenda, remains a very important issue." A more recent UN projection suggests the population could grow to as many as 15 billion by 2100.
In 2017, more than a third of 50 Nobel prize-winning scientists surveyed by the Times Higher Education at the Lindau Nobel Laureate Meetings said that human overpopulation and environmental degradation are the two greatest threats facing humankind. In November that same year, a statement by 15,364 scientists from 184 countries indicated that rapid human population growth is the "primary driver behind many ecological and even societal threats."
Human population
History of population growth
The human population has gone through a number of periods of growth since the dawn of civilization in the Holocene period, around 10,000 BCE. The beginning of civilization roughly coincides with the receding of glacial ice following the end of the last glacial period. It is estimated that between 1–5 million people, subsisting on hunting and foraging, inhabited the Earth in the period before the Neolithic Revolution, when human activity shifted away from hunter-gathering and towards very primitive farming.
Around 8000 BCE, at the dawn of agriculture, the population of the world was approximately 5 million. The next several millennia saw a steady increase in the population, with very rapid growth beginning in 1000 BCE, and a peak of between 200 and 300 million people in 1 BCE.
The Plague of Justinian caused Europe's population to drop by around 50% between 541 and the 8th century. Steady growth resumed in 800 CE. However, growth was again disrupted by frequent plagues; most notably, the Black Death during the 14th century. The effects of the Black Death are thought to have reduced the world's population, then at an estimated 450 million, to between 350 and 375 million by 1400. The population of Europe stood at over 70 million in 1340; these levels did not return until 200 years later. England's population reached an estimated 5.6 million in 1650, up from an estimated 2.6 million in 1500. New crops from the Americas via the Spanish colonizers in the 16th century contributed to the population growth.
In other parts of the globe, China's population at the founding of the Ming dynasty in 1368 stood close to 60 million, approaching 150 million by the end of the dynasty in 1644. The population of the Americas in 1500 may have been between 50 and 100 million.
Encounters between European explorers and populations in the rest of the world often introduced local epidemics of extraordinary virulence. Archaeological evidence indicates that the death of around 90% of the Native American population of the New World was caused by Old World diseases such as smallpox, measles, and influenza. Europeans introduced diseases alien to the indigenous people, therefore they did not have immunity to these foreign diseases.
After the start of the Industrial Revolution, during the 18th century, the rate of population growth began to increase. By the end of the century, the world's population was estimated at just under 1 billion. At the turn of the 20th century, the world's population was roughly 1.6 billion. By 1940, this figure had increased to 2.3 billion. Each subsequent addition of a billion humans took less and less time: 33 years to reach three billion in 1960, 14 years for four billion in 1974, 13 years for five billion in 1987, and 12 years for six billion in 1999.
Dramatic growth beginning in 1950 (above 1.8% per year) coincided with greatly increased food production as a result of the industrialization of agriculture brought about by the Green Revolution. The rate of human population growth peaked in 1964, at about 2.1% per year. For example, Indonesia's population grew from 97 million in 1961 to 237.6 million in 2010, a 145% increase in 49 years. In India, the population grew from 361.1 million people in 1951 to just over 1.2 billion by 2011, a 235% increase in 60 years.
There is concern over the sharp population increase in many countries, especially in Sub-Saharan Africa, that has occurred over the last several decades, and that it is creating problems with land management, natural resources and access to water supplies.
The population of Chad has, for example, grown from 6,279,921 in 1993 to 10,329,208 in 2009. Niger, Uganda, Nigeria, Tanzania, Ethiopia and the DRC are witnessing a similar growth in population. The situation is most acute in western, central and eastern Africa. Refugees from places like Sudan have further strained the resources of neighboring states like Chad and Egypt. Chad is also host to roughly 255,000 refugees from Sudan's Darfur region, and about 77,000 refugees from the Central African Republic, while approximately 188,000 Chadians have been displaced by their own civil war and famines, have either fled to either the Sudan, the Niger or, more recently, Libya.
According to UN data, there are on average 250 babies born each minute, or more than 130 million a year.
Projections of population growth
According to projections, the world population will continue to grow until at least 2050, with the population reaching 9 billion in 2040, and some predictions putting the population as high as 11 billion in 2050. The median estimate for future growth sees the world population reaching 8.6 billion in 2030, 9.8 billion in 2050 and 11.2 billion by 2100 assuming a continuing decrease in average fertility rate from 2.5 births per woman in 2010–2015 to 2.2 in 2045–2050 and to 2.0 in 2095–2100, according to the medium-variant projection.. Walter Greiling projected in the 1950s that world population would reach a peak of about nine billion, in the 21st century, and then stop growing, after a readjustment of the Third World and a sanitation of the tropics.
In 2000, the United Nations estimated that the world's population was growing at the rate of 1.14% (or about 75 million people) per year and according to data from the CIA's World Factbook, the world human population currently increases by 145 every minute.
According to the United Nations' World Population Prospects report:
The world population is currently growing by approximately 74 million people per year. Current United Nations predictions estimate that the world population will reach 9.0 billion around 2050, assuming a decrease in average fertility rate from 2.5 down to 2.0.
Almost all growth will take place in the less developed regions, where today's 5.3 billion population of underdeveloped countries is expected to increase to 7.8 billion in 2050. By contrast, the population of the more developed regions will remain mostly unchanged, at 1.2 billion. An exception is the United States population, which is expected to increase by 44% from 2008 to 2050.
In 2000–2005, the average world fertility was 2.65 children per woman, about half the level 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, Ethiopia, and China, listed according to the size of their contribution to population growth. China would be higher still in this list were it not for its one-child policy.
Global life expectancy at birth is expected to continue rising from 65 years in 2000–2005 to 75 years in 2045–2050. In the more developed regions, the projection is to 82 years by 2050. Among the least developed countries, where life expectancy today is just under 50 years, it is expected to increase to 66 years by 2045–2050.
The population of 51 countries or areas 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.
Birth rates are now falling in a small percentage of developing countries, while the actual populations in many developed countries would fall without immigration.
Urban growth
In 1800 only 3% of the world's population lived in cities. By the 20th century's close, 47% did so. In 1950 there were 83 cities with populations exceeding one million; but by 2007 this had risen to 468 agglomerations of more than one million. If the trend continues, the world's urban population will double every 38 years, according to researchers. The UN forecasts that today's urban population of 3.2 billion will rise to nearly 5 billion by 2030, when three out of five people will live in cities.
The increase will be most dramatic in the poorest and least-urbanised continents, Asia and Africa. Projections indicate that most urban growth over the next 25 years will be in developing countries. One billion people, one-seventh 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 unemployment, poverty, crime, drug addiction, alcoholism, and other social ills. 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, Beijing, Guangzhou, Seoul, Karachi, Mexico City, Mumbai, São Paulo, London 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 (at 34.1 million).
According to the Far Eastern Economic Review, Asia alone will have at least 10 'hypercities' by 2025, that is, cities inhabited by more than 19 million people, including Jakarta (24.9 million people), Dhaka (25 million), Karachi (26.5 million), Shanghai (27 million) and Mumbai (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.
Causes
From a historical perspective, technological revolutions have coincided with population expansion. There have been three major technological revolutions – the tool-making revolution, the agricultural revolution, and the industrial revolution – all of which allowed humans more access to food, resulting in subsequent population explosions. For example, the use of tools, such as bow and arrow, allowed primitive hunters greater access to more high energy foods (e.g. animal meat). Similarly, the transition to farming about 10,000 years ago greatly increased the overall food supply, which was used to support more people. Food production further increased with the industrial revolution as machinery, fertilizers, herbicides, and pesticides were used to increase land under cultivation as well as crop yields. Today, starvation is caused by economic and political forces rather than a lack of the means to produce food.
Significant increases in human population occur whenever the birth rate exceeds the death rate for extended periods of time. Traditionally, the fertility rate is strongly influenced by cultural and social norms that are rather stable and therefore slow to adapt to changes in the social, technological, or environmental conditions. For example, when death rates fell during the 19th and 20th century – as a result of improved sanitation, child immunizations, and other advances in medicine – allowing more newborns to survive, the fertility rate did not adjust downward, resulting in significant population growth. Until the 1700s, seven out of ten children died before reaching reproductive age. Today, more than nine out of ten children born in industrialized nations reach adulthood.
There is a strong correlation between overpopulation and poverty. In contrast, the invention of the birth control pill and other modern methods of contraception resulted in a dramatic decline in the number of children per household in all but the very poorest countries.
Agriculture has sustained human population growth. This dates back to prehistoric times, when agricultural methods were first developed, and continues to the present day, with fertilizers, agrochemicals, large-scale mechanization, genetic manipulation, and other technologies.
Humans have historically exploited the environment using the easiest, most accessible resources first. The richest farmland was plowed and the richest mineral ore mined first. Ceballos, Ehrlich A and Ehrlich P said that overpopulation is demanding the use of ever more creative, expensive and/or environmentally destructive means in order to exploit ever more difficult to access and/or poorer quality natural resources to satisfy consumers.
Demographic transition
The theory of demographic transition held that, after the standard of living and life expectancy increase, family sizes and birth rates decline. However, as new data has become available, it has been observed that after a certain level of development (HDI equal to 0.86 or higher) the fertility increases again and is often represented as a "J" shape. This means that both the worry that the theory generated about aging populations and the complacency it bred regarding the future environmental impact of population growth could need reevaluation.
Factors cited in the old theory included such social factors as later ages of marriage, the growing desire of many women in such settings to seek careers outside child rearing and domestic work, and the decreased need for 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 decline in birth rates in industrializing regions.
Many countries have high population growth rates but lower total fertility rates because high population growth in the past skewed the age demographic toward a young age, so the population still rises as the more numerous younger generation approaches maturity. "Demographic entrapment" is a concept developed by Maurice King, Honorary Research Fellow at the University of Leeds, who posits that this phenomenon 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 region is as follows:
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 2.49
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
Excluding the theoretical reversal in fertility decrease for high development, the projected world number of children born per woman for 2050 would be around 2.05. Only the Middle East & North Africa (2.09) and Sub-Saharan Africa (2.61) would then have numbers greater than 2.05.
Carrying capacity
Some groups (for example, the World Wide Fund for Nature and Global Footprint Network) have stated that the carrying capacity for the human population has been exceeded as measured using the Ecological Footprint. In 2006, WWF's "Living Planet Report" stated that in order for all humans to live with the current consumption patterns of Europeans, we would be spending three times more than what the planet can renew. Humanity as a whole was using, by 2006, 40 percent more than what Earth can regenerate. However, Roger Martin of Population Matters states the view: "the poor want to get rich, and I want them to get rich," with a later addition, "of course we have to change consumption habits,... but we've also got to stabilise our numbers". Another study by the World Wildlife Fund in 2014 found that it would take the equivalent of 1.5 Earths of biocapacity to meet humanity's current levels of consumption.
But critics question the simplifications and statistical methods used in calculating Ecological Footprints. Therefore, Global Footprint Network and its partner organizations have engaged with national governments and international agencies to test the results – reviews have been produced by France, Germany, the European Commission, Switzerland, Luxembourg, Japan and the United Arab Emirates. Some point out that a more refined method of assessing Ecological Footprint is to designate sustainable versus non-sustainable categories of consumption. However, if yield estimates were adjusted for sustainable levels of production, the yield figures would be lower, and hence the overshoot estimated by the Ecological Footprint method even higher.
Other studies give particular attention to resource depletion and increased world affluence.[further explanation needed]
In a 1994 study titled Food, Land, Population and the U.S. Economy, David Pimentel and Mario Giampietro estimated the maximum U.S. population for a sustainable economy at 200 million. And in order to achieve a sustainable economy and avert disaster, the United States would have to reduce its population by at least one-third, and world population would have to be reduced by two-thirds.
Many quantitative studies have estimated the world's carrying capacity for humans, that is, a limit to the world population. A meta-analysis of 69 such studies suggests a point estimate of the limit to be 7.7 billion people, while lower and upper meta-bounds for current technology are estimated as 0.65 and 98 billion people, respectively. They conclude: "recent predictions of stabilized world population levels for 2050 exceed several of our meta-estimates of a world population limit".
Effects of human overpopulation
Some more problems associated with or exacerbated by human overpopulation and over-consumption are:
Inadequate fresh water for drinking as well as sewage treatment and effluent discharge. Some countries, like Saudi Arabia, use energy-expensive desalination to solve the problem of water shortages.
Depletion of natural resources, especially fossil fuels.
Increased levels of air pollution, water pollution, soil contamination and noise pollution.
Changes in atmospheric composition and consequent global warming.
Loss of arable land and increase in desertification. Deforestation and desertification can be reversed by adopting property rights, and this policy is successful even while the human population continues to grow.
Mass species extinctions and contracting biodiversity 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. As of February 2011, the IUCN Red List lists a total of 801 animal species having gone extinct during recorded human history, although the vast majority of extinctions are thought to be undocumented. Biodiversity would continue to grow at an exponential rate if not for human influence. Sir David King, former chief scientific adviser to the UK government, told a parliamentary inquiry: "It is self-evident that the massive growth in the human population through the 20th century has had more impact on biodiversity than any other single factor." Paul and Anne Ehrlich said population growth is one of the main drivers of the Earth's extinction crisis.
High infant and child mortality. High rates of infant mortality are associated with poverty. Rich countries with high population densities have low rates of infant mortality. However, both global poverty and infant mortality has declined over the last 200 years of population growth.
Intensive factory farming to support large populations. It results in human threats including the evolution and spread of antibiotic resistant bacteria diseases, excessive air and water pollution, and new viruses that infect humans.
Increased chance of the emergence of new epidemics and pandemics. For many environmental and social reasons, including overcrowded living conditions, malnutrition and inadequate, inaccessible, or non-existent health care, the poor are more likely to be exposed to infectious diseases.
Starvation, malnutrition or poor diet with ill health and diet-deficiency diseases (e.g. rickets). However, rich countries with high population densities do not have famine.
Poverty coupled with inflation in some regions and a resulting low level of capital formation. Poverty and inflation are aggravated by bad government and bad economic policies. Many countries with high population densities have eliminated absolute poverty and keep their inflation rates very low.
Low life expectancy in countries with fastest growing populations. Overall life expectancy has increased globally despite of population growth, including countries with fast-growing populations.
Unhygienic living conditions for many based upon water resource depletion, discharge of raw sewage and solid waste disposal. However, this problem can be reduced with the adoption of sewers. For example, after Karachi, Pakistan installed sewers, its infant mortality rate fell substantially.
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.
Less personal freedom and more restrictive laws. Laws regulate and shape politics, economics, history and society and serve as a mediator of relations and interactions between people. The higher the population density, the more frequent such interactions become, and thus there develops a need for more laws and/or more restrictive laws to regulate these interactions and relations. It was even speculated by Aldous Huxley in 1958 that democracy is threatened due to overpopulation, and could give rise to totalitarian style governments. However, over the last 200 years of population growth, the actual level of personal freedom has increased rather than declined.
Many of these problems are explored in the dystopic science fiction film Soylent Green, where an overpopulated Earth suffers from food shortages, depleted resources and poverty and in the documentary "Aftermath: Population Overload".
David Attenborough described the level of human population on the planet as a multiplier of all other environmental problems. In 2013, he described humanity as "a plague on the Earth" that needs to be controlled by limiting population growth.
Most biologists and sociologists see overpopulation as a serious threat to the quality of human life. Some deep ecologists, such as the radical thinker and polemicist Pentti Linkola, see human overpopulation as a threat to the entire biosphere.
The effects of overpopulation are compounded by overconsumption. According to Paul R. Ehrlich:
Rich western countries are now siphoning up the planet’s resources and destroying its ecosystems at an unprecedented rate. We want to build highways across the Serengeti to get more rare earth minerals for our cellphones. We grab all the fish from the sea, wreck the coral reefs and put carbon dioxide into the atmosphere. We have triggered a major extinction event ... A world population of around a billion would have an overall pro-life effect. This could be supported for many millennia and sustain many more human lives in the long term compared with our current uncontrolled growth and prospect of sudden collapse ... If everyone consumed resources at the US level – which is what the world aspires to – you will need another four or five Earths. We are wrecking our planet’s life support systems.
Some economists, such as Thomas Sowell and Walter E. Williams argue that third world poverty and famine are caused in part by bad government and bad economic policies.
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