Human overpopulation


Human overpopulation is the idea that human populations may become too large to be sustained by their environment or resources in the long term. The topic is usually discussed in the context of world population, though it may concern individual nations, regions, and cities.
Since 1804, the global living human population has increased from 1 billion to 8 billion due to medical advancements and improved agricultural productivity. Annual world population growth peaked at 2.1% in 1968 and has since dropped to 1.1%. According to the most recent United Nations' projections, the global human population is expected to reach 9.7 billion in 2050 and would peak at around 10.4 billion people in the 2080s, before decreasing, noting that fertility rates are falling worldwide. Other models agree that the population will stabilize before or after 2100. Conversely, some researchers analyzing national birth registries data from 2022 and 2023—which cover half the world's population—argue that the 2022 UN projections overestimated fertility rates by 10 to 20% and were already outdated by 2024. They suggest that the global fertility rate may have already fallen below the sub-replacement fertility level for the first time in human history and that the global population will peak at approximately 9.5 billion by 2061. The 2024 UN projections report estimated that world population would peak at 10.29 billion in 2084 and decline to 10.18 billion by 2100, which was 6% lower than the UN had estimated in 2014.
Early discussions of overpopulation in English were spurred by the work of Thomas Malthus. Discussions of overpopulation follow a similar line of inquiry as Malthusianism and its Malthusian catastrophe, a hypothetical event where population exceeds agricultural capacity, causing famine or war over resources, resulting in poverty and environmental collapses. More recent discussion of overpopulation was popularized by Paul Ehrlich in his 1968 book The Population Bomb and subsequent writings. Ehrlich described overpopulation as a function of overconsumption, arguing that overpopulation should be defined by a population being unable to sustain itself without depleting non-renewable resources.
The belief that global population levels will become too large to sustain is a point of contentious debate. Those who believe global human overpopulation to be a valid concern, argue that increased levels of resource consumption and pollution exceed the environment's carrying capacity, leading to population overshoot. The population overshoot hypothesis is often discussed in relation to other population concerns such as population momentum, biodiversity loss, hunger and malnutrition, resource depletion, and the overall human impact on the environment.
Critics of the belief note that human population growth is decreasing and the population will likely peak, and possibly even begin to decrease, before the end of the century. They argue the concerns surrounding population growth are overstated, noting that quickly declining birth rates and technological innovation make it possible to sustain projected population sizes. Other critics claim that overpopulation concerns ignore more pressing issues, like poverty or overconsumption, are motivated by racism, or place an undue burden on the Global South, where most population growth happens.

Overview

Modern proponents of the concept have suggested that overpopulation, population growth and overconsumption are interdependent and collectively are the primary drivers of human-caused environmental problems such as climate change According to the Intergovernmental Panel on Climate Change Sixth Assessment Report, both GDP per capita and population growth remained the strongest drivers of CO₂ emissions from fossil fuel combustion during 2010–2019; population growth increased emissions by about 1.2% per year and GDP per capita by about 2.3% per year.
and biodiversity loss. Many scientists have expressed concern about population growth, and argue that creating sustainable societies will require decreasing the current global population. Advocates have suggested implementation of population planning strategies to reach a proposed sustainable population.
Overpopulation hypotheses are controversial, with many demographers and environmentalists disputing the core premise that the world cannot sustain the current trajectory of human population. Additionally, many economists and historians have noted that sustained shortages and famines have historically been caused by war, price controls, political instability, and repressive political regimes rather than overpopulation. They also note that population growth has historically led to greater technological development and the advancement of scientific knowledge. This has enabled the engineering of substitute goods and technology that better conserve and more efficiently use natural resources, increase agricultural output with less land and water, and address human impacts on the environment. These advancements result from increasing numbers of scientists, engineers, and inventors across generations, alongside increasing and continuous revision of scientific thinking. Instead, social scientists argue that disputes between themselves and biologists about human overpopulation are over the appropriateness of definitions being used.
Annual world population growth peaked at 2.1% in 1968, has since dropped to 1.1%, and could drop even further to 0.1% by 2100. Based on this, the United Nations projects the world population, which is 7.8 billion as of 2020, to level out around 2100 at 10.9 billion with other models proposing similar stabilization before or after 2100. Some experts believe that a combination of factors would allow global resources to meet this increased demand, avoiding global overpopulation. The debate is further complicated by a growing focus on the consequences of rapidly declining fertility rates in many nations, which presents risks of economic contraction and aging populations, offering a balanced perspective on global demographic challenges. Additionally, some critics dismiss the idea of human overpopulation as a science myth connected to attempts to blame environmental issues on overpopulation, oversimplify complex social or economic systems, or place blame on developing countries and poor populations—reinscribing colonial or racist assumptions and leading to discriminatory policy. These critics often suggest overconsumption should be treated as an issue separate from population growth.

History of world population

has been rising continuously since the end of the Black Death, around the year 1350. The fastest doubling of the world population happened between 1950 and 1986: a doubling from 2.5 to 5 billion people in 37 years, mainly due to medical advancements and increases in agricultural productivity. Due to its impact on the human ability to grow food, the Haber process enabled the global population to increase from 1.6 billion in 1900 to 7.7 billion by November 2018 and, according to the United Nations, eight billion as of November 2022. Some researchers have analyzed this growth in population like other animal populations, human populations predictably grow and shrink according to their available food supply as per the Lotka–Volterra equations, including agronomist and insect ecologist David Pimentel, behavioral scientist Russell Hopfenberg, and anthropologist Virginia Abernethy.
Year180618501900194019501960197019801990200020102020
Billions1.011.281.652.332.533.033.684.435.286.116.927.76

World population has experienced several periods of growth since the dawn of civilization in the Holocene period, around 10,000 BCE. The rise of civilization roughly coincided with the retreat of glacial ice following the end of the Last Glacial Period. The advent of farming enabled population growth in many regions of the world, including Europe, the Americas, and China, continuing through the 1600s, though occasionally interrupted by plagues or other crises. For example, the Black Death is thought to have reduced the world's population, then at an estimated 450 million in 1350, to between 350 and 375 million by 1400.
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. Even more dramatic growth beginning in 1950 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. Recent additions of a billion humans happened very quickly: 33 years to reach three billion in 1960, 14 years for four billion in 1974, 13 years for five billion in 1987, 12 years for six billion in 1999, 11 years for seven billion in 2010, and 12 years for 8 billion toward the end of 2022.

Future projections

Population projections are attempts to show how the human population might change in the future. These projections help to forecast the population's impact on this planet and humanity's future well-being. Models of population growth take trends in human development, and apply projections into the future to understand how they will affect fertility and mortality, and thus population growth.
The most recent report from the United Nations Population Division issued in 2022 projects that global population will peak around the year 2086 at about 10.4 billion, and then start a slow decline. As with earlier projections, this version assumes that the global average fertility rate will continue to fall, but even further from 2.5 births per woman during the 2015–2020 period to 1.8 by the year 2100.
However, other estimates predict additional downward pressure on fertility which could result in peak population during the 2060–2070 period rather than later.
According to the UN, of the predicted growth in world population between 2020 and 2050, all of that change will come from less developed countries, and more than half will come from just 8 African countries. It is predicted that the population of sub-Saharan Africa will double by 2050. The Pew Research Center predicts that 50% of births in the year 2100 will be in Africa. As an example of uneven prospects, the UN projects that Nigeria will gain about 340 million people, about the present population of the US, to become the 3rd most populous country, and China will lose almost half of its population.
Some scholars have argued that a form of "cultural selection" may be occurring due to significant differences in fertility rates between cultures, and it can therefore be expected that fertility rates and rates of population growth may rise again in the future. An example is certain religious groups that have a higher birth rate that is not accounted for by differences in income. In his book Shall the Religious Inherit the Earth?, Eric Kaufmann argues that demographic trends point to religious fundamentalists greatly increasing as a share of the population over the next century. From the perspective of evolutionary psychology, it is expected that selection pressure should occur for whatever psychological or cultural traits maximize fertility.