Short description: Condition where human numbers exceed the short or long-term carrying capacity of the environment
Different projections of the future human world population
Human overpopulation (or human population overshoot) is the concept of a human population becoming too large to be sustained by its environment or resources in the long term. The idea is usually discussed in the context of world population, though it may also concern regions. Human population growth has increased in recent centuries due to medical advancements and improved agricultural productivity. Those concerned by this trend argue that it results in a level of resource consumption which exceeds the environment's carrying capacity, leading to population overshoot. The concept is often discussed in relation to other population concerns such as demographic push and depopulation, as well as in relation to resource depletion and the human impact on the environment.
Recent discussion of overpopulation was popularized by Paul Ehrlich in his 1968 book The Population Bomb. Ehrlich described overpopulation as a function of overconsumption,[3] arguing that overpopulation should be defined by a population being unable to sustain itself without depleting non-renewable resources.[4][5][6] Modern proponents of the concept have suggested a link between overpopulation and human-caused environmental issues such as global warming and biodiversity loss, and other societal problems.[7][8] To mitigate this, population planning strategies have been advocated to establish what proponents consider a sustainable population.
The concept of overpopulation is controversial. Demographic projections suggest that population growth will stabilise in the 21st century, and many experts believe that global resources can meet this increased demand, suggesting a global overpopulation scenario is unlikely.[9][10] Critics highlight how attempts to blame environmental issues on overpopulation tend to oversimplify complex social or economic systems, or place blame on developing countries and poor populations—reinscribing colonial or racist assumptions.[2][11][12] For these reasons, critics of overpopulation suggest overconsumption be treated as an issue separate from population growth.[13][14]
Concerns about population size or density have a long history: Tertullian, a resident of the city of Carthage in the second century CE, criticized population at the time saying "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."[15] Despite these concerns, scholars have not found historic societies which have collapsed because of overpopulation or overconsumption.[16]
By the beginning of the 19th century, 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 limitless potential for increase.[17] During the 19th century, Malthus' work, particularly An Essay on the Principle of Population, 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.[18] This resulted, for example, in the English poor laws of 1834[18] and a hesitating response to the Irish Great Famine of 1845–52.[19]
Paul R. Ehrlich's book The Population Bomb became a bestseller upon its release in 1968, creating renewed interest in overpopulation. The book predicted population growth would lead to famine, societal collapse, and other social, environmental and economic strife in the coming decades, and advocated for policies to curb it.[4][12][20] The Club of Rome published the influential book The Limits to Growth in 1972, which similarly used computer modelling to argue that continued population growth trends would lead to global system collapse.[21] The idea of overpopulation was also a topic of some works of English-language science fiction and dystopian fiction during the latter part of the 1960s.[20]Human population and family planning policies were adopted by some nations in the late 20th century in an effort to curb population growth, including in China and India.[22]Albert Allen Bartlett gave more than 1,742 lectures on the threat of exponential population growth starting in 1969.[23]
However, many predictions of overpopulation during the 20th century did not materialise.[20][12] In The Population Bomb, Elrich stated that "[i]n the 1970s hundreds of millions of people will starve to death in spite of any crash programs embarked upon now,"[24] with later editions changing to instead be "in the 1980s".[1] Despite admitting some of his earlier predictions did not come to pass, Ehlrich continues to advocate that overpopulation is a major issue.[20]
As the profile of environmental issues facing humanity increased during the end of the 20th and early 21st centuries, some have looked to population growth as a root cause. A 2015 survey from Pew Research Center reports that 82% of scientists associated with the American Association for the Advancement of Science were concerned about population growth.[25] In 2017, more than one-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 mankind.[7] In November that same year, the World Scientists' Warning to Humanity: A Second Notice, signed by 15,364 scientists from 184 countries, indicated that rapid human population growth is "a primary driver behind many ecological and even societal threats."[26] Elrich and other scientists at a conference in the Vatican on contemporary species extinction linked the issue to population growth in 2017, and advocated for human population control, which attracted controversy from the Catholic church.[27] In 2019, a warning on climate change signed by 11,000 scientists from 153 nations said that human population growth adds 80 million humans annually, and "the world population must be stabilized—and, ideally, gradually reduced—within a framework that ensures social integrity" to reduce the impact of "population growth on GHG emissions and biodiversity loss."[28][29]
Myths and misinformation about overpopulation of Rohingya people in Myanmar is thought to have driven their persecution in the 2010s.[30] The Indian government of Narendra Modi introduced population policies in the 21st century, including offering incentives for sterilization, citing the risks of a "population explosion", although demographers have criticised this basis, with India thought to be undergoing demographic transition and the fertility rate falling. The policies have also received criticism from human and women's rights groups.[31][32] Some scientists, including William J. Ripple, argue that while the "abhorrent history" of draconian "population control" programs including forced sterilization campaigns and China's one-child policy "must be acknowledged and
never repeated," we should not use such history to justify ignoring sensible population policies that could advance social justice (such as by abolishing child marriage, expanding family planning services and reforms that improve education for women and girls) and at the same time mitigate the human impact on the climate, biodiversity and the ecosystem by slowing fertility rates.[33]
In 2020, a quote from David Attenborough about how humans have "overrun the planet" was shared widely online, becoming his most popular comment on the internet.[34]
Advocacy organizations
Population concern organizations have promoted the conversation in academic and policy circles. Organizations focused on population stabilization and population concern often focus on the policy of particular governments, or particular solutions to overpopulation. Some of these organizations are popular or visible because of their association with major public figures, such as Population Matters' connection with David Attenborough, while others are more closely associated with particular academic interpretations or solutions.[citation needed]
Global population dynamics, their history and factors
Map of countries and territories by fertility rate (See List of countries and territories by fertility rate.)
Human population growth rate in percent, with the variables of births, deaths, immigration, and emigration – 2018
World population has been rising continuously since the end of the Black Death, around the year 1350.[35] The fastest doubling of the world population happened between 1950 and 1986: a doubling from 2.5 to 5 billion people in just 37 years, [36] mainly due to medical advancements and increases in agricultural productivity.[37][38] Due to its dramatic impact on the human ability to grow food, the Haber process enabling the global population to increase from 1.6 billion in 1900 to 7.7 billion by November 2018.[39]
Some researchers analyze this growth in population like other animal populations, human populations predictably grow and shrink according to their available food supply (see Lotka–Volterra equations), including agronomist and insect ecologist David Pimentel,[40] behavioral scientist Russell Hopfenberg,[41] and anthropologist Virginia Abernethy.[42]
World 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.[45]Farming allowed for the growth of populations in many parts of the world, including Europe, the Americas and China through the 1600s, occasionally disrupted by plagues or other crisis.[46][47] For example, the Black Death is thought to have reduced the world's population, then at an estimated 450 million, to between 350 and 375 million by 1400.[48]
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.[49] At the turn of the 20th century, the world's population was roughly 1.6 billion.[49] 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.[50] The rate of human population growth peaked in 1964, at about 2.1% per year.[51] By 1940, this figure had increased to 2.3 billion.[52] 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.[53]
On 14 May 2018 , the United States Census Bureau calculates 7,472,985,269 for that same date[54] and the United Nations estimated over 7 billion.[55][56][57] In 2017, the United Nations increased the medium variant projections[58] to 9.8 billion for 2050 and 11.2 billion for 2100.[59] The UN population forecast of 2017 was predicting "near end of high fertility" globally and anticipating that by 2030 over ⅔ of the world population will be living in countries with fertility below the replacement level[60] and for total world population to stabilize between 10 and 12 billion people by the year 2100.[61]
Map of population density by country, per square kilometer. (See List of countries by population density.)
Proposed impacts
Biologists and sociologists have discussed overpopulation as a threat to the quality of human life.[62][63] Some environmentalists, such as Pentti Linkola, have argued human overpopulation represents a threat to Earth's biosphere.[64]
Poverty, and infant and child mortality
Although proponents of human overpopulation have expressed concern that growing population will lead to an increase in global poverty and infant mortality, both indicators have declined over the last 200 years of population growth.[9][65]
Environmental impacts
Having one less child, on average, saves 58.6 tonnes of CO2 equivalent per year.
It has been suggested[by whom?] that overpopulation has substantially adversely impacted the environment of Earth starting at least as early as the 20th century.[63][verification needed] There are also economic consequences of environmental degradation caused by excess waste production and overconsumption in the form of ecosystem services attrition.[66] A number of scientists have argued that the looming human impact on the environment and accompanying increase in resource consumption threatens the world's ecosystem and the survival of human civilization.[67][68][69][8] The InterAcademy Panel Statement on Population Growth, which was ratified by 58 member national academies in 1994, states that "unprecedented" population growth aggravates many environmental problems, including rising levels of atmospheric carbon dioxide, global warming, and pollution.[70] Indeed, some analysts claim that overpopulation's most serious impact is its effect on the environment.[71] Some scientists suggest that the overall human impact on the environment during the Great Acceleration, particularly due to human population size and growth, economic growth, overconsumption, pollution, and proliferation of technology, has pushed the planet into a new geological epoch known as the Anthropocene.[72][73]
However, even in countries which have both large population growth and major ecological problems, it is not necessarily true that curbing the population growth will make a major contribution towards resolving all environmental problems.[74]
Some studies and commentary link population growth with climate change.[28][77][78][79][33] Critics have stated that population growth alone may have less influence on climate change than other factors, such as greenhouse gas emissions per capita.[80][21] The global consumption of meat is projected to rise by as much as 76% by 2050 as the global population increases, with this projected to have further environmental impacts such as biodiversity loss and increased greenhouse gas emissions.[81][82] A July 2017 study published in Environmental Research Letters argued that the most significant way individuals could mitigate their own carbon footprint is to have fewer children, followed by living without a vehicle, forgoing air travel, and adopting a plant-based diet.[83]
Continued population growth and overconsumption, particularly by the wealthy, have been posited as key drivers of biodiversity loss and the 6th (and ongoing) mass extinction,[84][85][8] with some researchers and environmentalists specifically suggesting this indicates a human overpopulation scenario.[86][87] The Global Assessment Report on Biodiversity and Ecosystem Services, released by IPBES in 2019, states that human population growth is a factor in biodiversity loss.[88][89]
Human overpopulation and continued population growth are also considered by some to be an animal rights issue, as more human activity means the destruction of animal habitats and more direct killing of animals.[92][81]:146
Resource depletion
Some commentary has attributed depletion of non-renewable resources, such as land, food and water, to overpopulation[93] and suggested it could lead to a diminished quality of human life.[63] Ecologist David Pimentel was one such proponent, saying "with the imbalance growing between population numbers and vital life sustaining resources, humans must actively conserve cropland, freshwater, energy, and biological resources. There is a need to develop renewable energy resources. Humans everywhere must understand that rapid population growth damages the Earth's resources and diminishes human well-being."[94][95]
Although food shortages have been warned as a consequence of overpopulation, according to the Food and Agriculture Organization, global food production exceeds increasing demand from global population growth.[23] Food insecurity in some regions is attributable to the globally unequal distribution of food supplies.[23] Some proponents of overpopulation[who?] warn expansion of agricultural production to meet population growth is likely to have a substantial impact on the environment, and have expressed concern at usable land area becoming limited.[96][97][98]
The notion that space is limited has been decried by skeptics, who point out that the Earth's population of roughly 6.8 billion people could comfortably be housed an area comparable in size to the state of Texas, in the United States (about 269,000 square miles or 696,706.80 square kilometres).[97] Critics suggest changes to policies relating to land use or agriculture would be more likely to resolve land shortage issues.[80]
Growth in food production has been greater than population growth.
Percentage of population suffering from undernourishment by country, according to United Nations statistics.
Political systems
It was speculated by Aldous Huxley in 1958 that democracy is threatened by overpopulation, and could give rise to totalitarian style governments.[103] Physics professor Albert Allen Bartlett at the University of Colorado Boulder warned in 2000 that overpopulation and the development of technology are the two major causes of the diminution of democracy.[104] However, over the last 200 years of population growth, the actual level of personal freedom has increased rather than declined.[65]
Some groups (for example, the World Wide Fund for Nature[106][107] and Global Footprint Network) have stated that the yearly biocapacity of Earth is being 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.[108] Humanity as a whole was using, by 2006, 40 percent more than what Earth can regenerate.[109] 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".[110] 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.[111]
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.[112] Some point out that a more refined method of assessing Ecological Footprint is to designate sustainable versus non-sustainable categories of consumption.[113][114]
Carrying capacity
Many attempts have been made to estimate the world's carrying capacity for humans; the maximum population the world can host.[115] A 2004 meta-analysis of 69 such studies from 1694 until 2001 found the average predicted maximum number of people the Earth would ever have was 7.7 billion people, with lower and upper meta-bounds at 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".[116]
A 2012 United Nations report summarized 65 different estimated maximum sustainable population sizes and the most common estimate was 8 billion.[117] Advocates of reduced population often put forward much lower numbers. Paul R. Ehrlich stated in 2018 that the optimum population is between 1.5 and 2 billion.[118] Geographer Chris Tucker estimates that 3 billion is a sustainable number.[119]
Critics of overpopulation criticize the basic assumptions associated with these estimates. For example, Jade Sasser believes that calculating a maximum of number of humanity is unethical while only some, mostly privileged European former colonial powers, are mostly responsible for unsustainably using up Earth's resources.[120]
Proposed solutions and mitigation measures
Several strategies have been proposed to mitigate overpopulation.
Population planning
Proposed population planning approaches include:
Improved access to contraception
Reducing infant mortality, so that parents do not need to have many children to ensure at least some survive to adulthood.[121]
Improving the status of women in order to facilitate a departure from traditional sexual division of labour.
A family planning placard in Ethiopia. It shows some negative effects of having more children than people can care for.
Education and empowerment of women and giving access to family planning and contraception have demonstrated positive impacts on reducing birthrates.[123] Many studies conclude that educating girls reduces the number of children they have.[123] One option according to some activists is to focus on education about family planning and birth control methods, and to make birth-control devices like condoms, contraceptive pills and intrauterine devices easily available. Worldwide, nearly 40% of pregnancies are unintended (some 80 million unintended pregnancies each year).[124] An estimated 350 million women in the poorest countries of the world 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 annually of complications from pregnancy and abortion,[125] with 86% of these deaths occurring in the sub-Saharan Africa region and South Asia.[126] Additionally, 8 million infants die, many because of malnutrition or preventable diseases, especially from lack of access to clean drinking water.[127]
Women's rights and their reproductive rights in particular are issues regarded to have vital importance in the debate.[128] This incentive, however, has been questioned by Rosalind Pollack Petchesky. Citing his attendance of the 1994 Cairo conference, he reported that overpopulation and birth control were being diverted by feminists into women's rights issues, mostly downplaying the overpopulation issue as only one minor matter of many others; most of these focusing on women's rights. Upon his observation, he argued this was forging many faults and distractions on the main problem of human overpopulation and how to solve it.[129]
Ehrlich advocated in The Population Bomb that "various forms of coercion", such as removing tax benefits for having additional children, be used in cases when voluntary population planning policies fail.[20] Some nations, like China , have used strict or coercive measures such as the one-child policy to reduce birth rates.[130]Compulsory sterilization has also been implemented in many countries as a form of population control.[131][22]
Another choice-based approach is financial compensation or other benefits by the state offered to people who voluntarily undergo sterilization. Such policies have been introduced by the government of India.[132][133][31]
Despite the increase in population density within cities (and the emergence of megacities), UN Habitat states in its reports that urbanization may be the best compromise in the face of global population growth.[134] Cities concentrate human activity within limited areas, limiting the breadth of environmental damage.[135] UN Habitat says this is only possible if urban planning is significantly improved.[136]
Paul Ehrlich pointed out in his book The Population Bomb (1968) argues that rhetoric supporting the increase of city density as a means of avoiding dealing with the actual problem of overpopulation to begin with and rather than treating the increase of city density as a symptom of the root problem, it has been promoted by the same interests that have profited from population increase e.g. property developers, the banking system, which invests in property development, industry, municipal councils etc.[137] Subsequent authors point to growth economics as driving governments seek city growth and expansion at any cost disregarding the impact it might have on the environment.[138]
Criticism
Global fertility rates as of 2020. About half of the world population lives in nations with sub-replacement fertility.[139]
The concept of human overpopulation, and its attribution as a cause of environmental issues, are controversial.[10][12][140][13][34]
Some critics refer to overpopulation as a myth.[23][97][141][142][14][143] Predicted exponential population growth or any "population explosion" did not materialise; instead, population growth slowed.[20][31] Critics suggest that enough resources are available to support projected population growth, and that human impacts on the environment are not attributable to overpopulation.[90][34][142] According to libertarian think tank the Fraser Institute, both the idea of overpopulation and the alleged depletion of resources are myths; most resources are now more abundant than a few decades ago, thanks to technological progress.[144] The Institute is also questioning the sincerity of advocates of population control in poor countries.[144][145]
Demographer Nicholas Eberstadt has criticised the idea of overpopulation, saying that "overpopulation is not really overpopulation. It is a question of poverty".[23]
A 2020 study in The Lancet concluded that "continued trends in female educational attainment and access to contraception will hasten declines in fertility and slow population growth", with projections suggesting world population would peak at 9.73 billion in 2064 and fall by 2100.[146] Media commentary interpreted this as suggesting overconsumption represents a greater environmental threat as an overpopulation scenario may never occur.[10][147]
Some human population planning strategies advocated by proponents of overpopulation are controversial for ethical reasons. Those concerned with overpopulation, including Paul Elrich, have been accused of influencing human rights abuses including forced sterilisation policies in India and under China's one-child policy, as well as mandatory or coercive birth control measures taken in other countries.[22][133][31][148]
Women's rights
Influential advocates such as Betsy Hartmann consider the "myth of overpopulation" to be destructive as it “prevents constructive thinking and action on reproductive rights,” which acutely effects women and communities of women in poverty.[141] The 1994 International Conference on Population and Development (ICPD) define reproductive rights as “the basic right of all couples and individuals to decide freely and responsibly the number, spacing, and timing of their children and to have the information to do so."[149] This oversimplification of human overpopulation leads individuals to believe there are simple solutions and the creation of population policies that limit reproductive rights.
Scholar Heather Alberro argues to reject the overpopulation argument, stating that the human population growth is rapidly slowing down, the underlying problem is not the number of people, but how resources are distributed and that the idea of overpopulation could fuel a racist backlash against the population of poor countries.[90]
Racism
The argument of overpopulation has been criticized by some scholars and environmentalists as being racist and having roots in colonialism and white supremacy, since control and reduction of human population is often focused on the global south, instead of on overconsumption and the global north.[140][150][13][90][151]Paul Ehrlich's Population Bomb begins with him describing first knowing the "feel of overpopulation" from a visit to Delhi, which some critics have accused of having racial undertones.[152]George Monbiot has said "when affluent white people wrongly transfer the blame for their environmental impacts on to the birthrate of much poorer brown and black people, their finger-pointing reinforces [white genocide conspiracy] narratives. It is inherently racist."[153] Overpopulation is said to be a common component of ecofascist ideology.[150][34]
By public figures
Some billionaires have expressed concern that impending population collapse is the greatest ecological threat, more so than pollution, environmental degradation or climate change.[154]Elon Musk is a vocal critic of the idea of overpopulation. According to Musk, proponents of the idea are misled by their immediate impressions from living in dense cities.[155] Because of the negative replacement rates in many countries, he expects that by 2039 the biggest issue will be population collapse, not explosion.[156] Jack Ma expressed a similar opinion.[156] However, these sentiments are not supported by data and most population projections point to the human population reaching at least 10 billion people by 2100.[157][154]
↑ 4.04.1Ehrlich, Paul R. Ehrlich & Anne H. (1990). The population explosion. London: Hutchinson. pp. 39–40. ISBN978-0091745516. https://archive.org/details/populationexplos00ehrl/page/39. Retrieved 20 July 2014. "When is an area overpopulated? When its population cannot be maintained without rapidly depleting nonrenewable resources [39] (or converting renewable resources into nonrenewable ones) and without decreasing the capacity of the environment to support the population. In short, if the long-term carrying capacity of an area is clearly being degraded by its current human occupants, that area is overpopulated."
↑Ehrlich, Paul R; Ehrlich, Anne H (2004), One with Nineveh: Politics, Consumption, and the Human Future, Island Press/Shearwater Books, pp. 76–180, 256
↑Ehrlich, Paul R; Ehrlich, Anne H (1991), Healing the Planet: Strategies for Resolving the Environmental Crisis, Addison-Wesley Books, pp. 6–8, 12, 75, 96, 241
↑ 8.08.18.2Bradshaw, Corey J. A.; Ehrlich, Paul R.; Beattie, Andrew; Ceballos, Gerardo; Crist, Eileen; Diamond, Joan; Dirzo, Rodolfo; Ehrlich, Anne H. et al. (2021). "Underestimating the Challenges of Avoiding a Ghastly Future". Frontiers in Conservation Science1. doi:10.3389/fcosc.2020.615419. "Large populations and their continued growth are also drivers of soil degradation and biodiversity loss. More people means that more synthetic compounds and dangerous throw-away plastics are manufactured, many of which add to the growing toxification of the Earth.".
↑ 18.018.1Gregory Claeys: The "Survival of the Fittest" and the Origins of Social Darwinism, in Journal of the History of Ideas, Vol. 61, No. 2, 2002, p. 223–240
↑Cormac Ó Gráda: Famine. A Short History, Princeton University Press 2009, ISBN:978-0-691-12237-3 (pp. 20, 203–206)
↑Pimentel, David. "Overpopulation and sustainability." Petroleum Review 59 (2006): 34–36.
↑Hayami, Yujiro, and Vernon W. Ruttan. "Population growth and agricultural productivity." Technological Prospects and Population Trends. Routledge, 2020. 11–69.
↑Syvitski, Jaia et al. (2020). "Extraordinary human energy consumption and resultant geological impacts beginning around 1950 CE initiated the proposed Anthropocene Epoch". Communications Earth & Environment1 (32): 32. doi:10.1038/s43247-020-00029-y. Bibcode: 2020ComEE...1...32S. ""Human population has exceeded historical natural limits, with 1) the development of new energy sources, 2) technological developments in aid of productivity, education and health, and 3) an unchallenged position on top of food webs. Humans remain Earth’s only species to employ technology so as to change the sources, uses, and distribution of energy forms, including the release of geologically trapped energy (i.e. coal, petroleum, uranium). In total, humans have altered nature at the planetary scale, given modern levels of human-contributed aerosols and gases, the global distribution of radionuclides, organic pollutants and mercury, and ecosystem disturbances of terrestrial and marine environments. Approximately 17,000 monitored populations of 4005 vertebrate species have suffered a 60% decline between 1970 and 2014, and ~1 million species face extinction, many within decades. Humans' extensive 'technosphere', now reaches ~30 Tt, including waste products from non-renewable resources."".
↑ 81.081.1Best, Steven (2014). The Politics of Total Liberation: Revolution for the 21st Century. Palgrave Macmillan. p. 160. ISBN978-1137471116. "By 2050 the human population will top 9 billion, and world meat consumption will likely double."
↑Lin, Doris (July 3, 2019). "Human Overpopulation". https://www.thoughtco.com/effects-of-human-overpopulation-127867. "Human overpopulation is an animal rights issue as well as an environmental issue and a human rights issue. Human activities, including mining, transportation, pollution, agriculture, development, and logging, take habitat away from wild animals as well as kill animals directly."
↑Cohen, J.E. (1995). How many people can the earth support? W.W. Norton & Company, New York, NY, USA.
↑Van Den Bergh, Jeroen C. J. M.; Rietveld, Piet (2004). "Reconsidering the Limits to World Population: Meta-analysis and Meta-prediction". BioScience54 (3): 195. doi:10.1641/0006-3568(2004)054[0195:RTLTWP2.0.CO;2]. ISSN0006-3568.
↑Sasser, Jade (13 November 2018). On infertile ground : population control and women's rights in the era of climate change. New York. ISBN978-1-4798-7343-2. OCLC1029075188.
↑Lifeblood: How to Change the World One Dead Mosquito at a Time, Alex Perry p9
↑ 122.0122.1Ryerson, William N. (2010). The Post Carbon Reader: Managing the 21st Century's Sustainability Crises, "Ch.12: Population: The Multiplier of Everything Else". Healdsburg, Calif.: Watershed Media. pp. 153–174. ISBN978-0970950062.
↑UNFPA (1994). Programme of Action: Adopted at the International Conference of Population and development, Cairo, 5–13 September 1994.. UN Population Fund. pp. Section 7.3. ISBN0-89714-696-4.
David Foreman, Man Swarm: How Overpopulation is Killing the Wild World. Livetrue Books, 2015. ISBN:978-0986383205
Karen Shragg, Move Upstream: A Call to Solve Overpopulation.ISBN:978-0988493834 (published November 2015). Discussion of the book by the author, March 2017 (video, 91 minutes).
Alan Weisman. Countdown: Our Last, Best Hope for a Future on Earth? Little, Brown and Company, (2013) ISBN:0316097756