In environmental science, a populationovershoots its local carrying capacity—the maximum population size that an ecosystem can sustainably support—when it exceeds the availability of resources needed for survival. This can lead to a population crash if resources are depleted faster than they can regenerate. Overshoot applies to humans as well as other animal populations: any species that relies on consumption of resources to survive.[1][2]
Population decline due to overshoot is known as 'collapse'. The path taken by such a population is referred to as 'overshoot-and-collapse'. Collapse, like overshoot, can occur due to various factors, with theMalthusian catastrophe being a specific but not identical case.[6][7][8]
Overshoot can happen as a result of delayed impacts, wherereproduction rates persistently surpass thedeath rate.[9] This can lead to significant consequences, with entireecosystems being profoundly impacted and sometimes simplified due to prolonged overshoot.[10] An instance of this phenomenon took place in theHorn of Africa whensmallpox was eradicated, causing a sudden increase in the population that exceeded the region's carrying capacity. For centuries, the land had sustained approximately 1 millionpastoralists, but with the elimination of the disease, the population suddenly grew to 14 million people. Consequently,overgrazing occurred, leading to soil erosion.[11]
The most famous example of an overshoot-and-crash may be fromSt. Matthew Island. In 1944, 29 reindeer were introduced to the island, which by 1963 had grown to a peak population of roughly 6000 individuals — well past the estimatedcarrying capacity. At next count, in 1965, the population had plummeted and only 42 reindeer were left alive.
Thomas Malthus (1766-1864) is perhaps the most well-known writer to have articulated the roots of the modern concept of human overshoot, withThe Population Bomb (1967) by Paul Ehrlich reigniting the hotly-debated topic in more recent history.Daniel Quinn claims to have modernized the concept ofhuman overpopulation in what are likely the most well-read volumes to have given it extensive treatmentas a subject of ecology:The Story of B (1996) andMy Ishmael (1997).
This sectionshould include only abrief summary ofHuman overpopulation. SeeWikipedia:Summary style for information on how to properly incorporate it into this article's main text.(October 2021)
The 1972 bookThe Limits to Growth discussed the limits to growth of society as a whole. This book included a computer-based model which predicted that the Earth would reach acarrying capacity of ten to fourteen billion people after some two hundred years, after which the human population would collapse.[12] The model was based on five variables: "population, food production, industrialization, pollution, andconsumption of non-renewable natural resources".[13]: 25 This simulation modelled human populations after the overshoot and collapse seen in all unmoderated species. It was controversial and generally dismissed by economists.[14]
SociologistWilliam R. Catton, Jr. explored the connections between human societies and the natural environment in his bookOvershoot published in 1980. Catton expressed his concerns about the global population exceeding Earth's sustainable limits, advocating that a reduction in population through natural means, such as mortality, was necessary. He argued that the predicament stemmed from bothoverpopulation, where the number of people surpassed what the planet could support, andoverconsumption, referring to the excessive utilization of resources. Catton predicted that unless these issues were addressed, humanity would surpass the Earth's optimal carrying capacity, leading to potentially dire consequences.[15][16][17]
TheGlobal Footprint Network purports to be able to measure how much the human economy demands against what the Earth can renew.[18][19] The Optimum Population Trust (now calledPopulation Matters) has listed what they believe is the overshoot (overpopulation) of a number of countries, based on the above.[20]
In one study[21] published in January 2021 inFrontiers in Conservation Science, the significance of overshoot is discussed. It says that alongside the growth of the global population, humanity's consumption relative to Earth's regenerative capacity has surged by 73% in 1960 to 170% in 2016, particularly incountries with higher incomes.[22] These findings are based on recentecological footprint studies.[23]
An article inFrontiers in Conservation Science also says ecological overshoot has been facilitated by the increasing reliance on fossil fuels. The widespread use of convenient energy sources has allowed human demand to detach from the limits ofbiological regeneration. Notably, fossil fuels account for 85% of commercial energy production, 65% of fiber production, and serve as the primary raw material for most plastics.[22]
As a possible cause forsocietal collapse, overshoot has been scholarly discussed, but has not been found having been the cause for historic cases of collapse.[24]
Greater Los Angeles lies on a coastal mediterraneansavannah with a smallwatershed that is able to support at most one million people onits own water; as of 2015, the area has a population of over 18 million. Researchers predict that similar cases of resource scarcity will grow more common as the world population increases.[25]
The predictions of Ehrlich and otherneo-Malthusians were challenged by a number of economists, notablyJulian Lincoln Simon, who said advances in agriculture, collectively known as theGreen Revolution, forestalled any potential global famine in the late 20th century. Notably, between 1950 and 1984, the Green Revolution transformed agriculture around the world and grain production increased by over 250%.[27] The world population has grown by over four billion since the beginning of the Green Revolution, but food production has so far kept pace with population growth. Most scholars believe that, without the Green Revolution, there would be greater levels of famine and malnutrition than the UN presently documents.[28] However, neo-Malthusians point out thatfossil fuels provided the energy for the Green Revolution, in the form of natural gas-derivedfertilizers, oil-derivedpesticides, andhydrocarbon-fueledirrigation, and that many crops have become so genetically uniform that a crop failure in any one country could potentially have global repercussions.[29]
In May 2008, the price of grain rose because of the increased cultivation ofbiofuels, the increase of worldoil prices to over $140 per barrel ($880/m3),[30] global population growth,[31] the effects ofclimate change,[32] the loss of agricultural land to residential and industrial development,[33][34] and growing consumer demand in the population centres of China and India.[35][36]Food riots subsequently occurred in some countries.[37][38] However, oil prices then fell sharply. Resource demands are expected to ease as population growth declines, but it is unclear whether massfood wastage and rising living standards in developing countries will once again create resource shortages.[39][40]
David Pimentel, professor of ecology and agriculture atCornell University, estimates that the sustainable agricultural carrying capacity for the United States is about 200 million people; its population as of 2015 is over 300 million.[41] In 2009, the UK government's chief scientific advisor, ProfessorJohn Beddington, warned that growing populations, falling energy reserves and food shortages would create a "perfect storm" of shortages of food, water, and energy by 2030.[25][42] According to a 2009 report by the United NationsFood and Agriculture Organization (FAO), the world will have to produce 70% more food by 2050 to feed a projected extra 2.3 billion people.[43]
The figures for 2007 showed an actual increase in absolute numbers of undernourished people in the world, with 923 million undernourished in 2007, versus 832 million in 1995.[44] The 2009 FAO estimates showed an even more dramatic increase, to 1.02 billion.[45]
The inward spiral shows how humans have progressively used more of Earth's resources than the planet can regenerate. Earth's ability to regenerate consumed resources now lasts only about 57% as long as in 1971.[46]Illegalslash-and-burn agriculture inMadagascar, 2010
A government sign in China: "For a prosperous, powerful nation and a happy family, please practice family planning."
Human population planning is the practice of intervening to alter the rate of population growth. Historically, human population control has been implemented by limiting a region'sbirth rate, by voluntary contraception or by government mandate. It has been undertaken as a response to factors including high or increasing levels of poverty,environmental concerns, andreligious reasons. The use ofabortion in some population control strategies has caused controversy,[55] with religious organizations such as theRoman Catholic Church explicitly opposing any intervention in the human reproductive process.[56]
TheUniversity of Nebraska–Lincoln publicationGreen Illusions argues that population control to alleviate environmental pressures need not be coercive. It states that "Women who are educated, economically engaged, and in control of their own bodies can enjoy the freedom of bearing children at their own pace, which happens to be a rate that is appropriate for the aggregate ecological endowment of our planet."[57] The bookFatal Misconception by Matthew Connelly similarly points to the importance of supporting the rights of women in bringing population levels down over time.[58]Paul Ehrlich also advocates making "modern contraception and back-up abortion available to all and give women full equal rights, pay and opportunities with men," noting that it could possibly "lead to a low enough total fertility rate that the needed shrinkage of population would follow. [But] it will take a very long time to humanely reduce total population to a size that is sustainable." Ehrlich places the optimum global population size at 1.5 to 2 billion people.[59]
Other academicians and public figures have pointed to the role of agriculture andagricultural productivity of increasing humancarrying capacity, which results in population overshoot, as with any other species when their food supply experiences an increase, which in turn results in resource depletion and mass poverty and starvation in the case of humans.[60][61][62][63]
^Ryerson, W. F. (2010), "Population, The Multiplier of Everything Else", in McKibben, D. (ed.),The Post Carbon Reader: Managing the 21st Century Sustainability Crisis, Watershed Media,ISBN978-0-9709500-6-2
^Brown, L. R. (2011).World on the Edge. Earth Policy Institute. Norton.ISBN978-0-393-08029-2.
^Mathis Wackernagel, Niels B. Schulz, Diana Deumling, Alejandro Callejas Linares, Martin Jenkins, Valerie Kapos, Chad Monfreda, Jonathan Loh, Norman Myers Richard Norgaard and Jørgen Rander (May 16, 2002)."Tracking the ecological overshoot of the human economy". Retrieved 2 August 2016.
^abcBradshaw, Corey J. A.; Ehrlich, Paul R.; Beattie, Andrew; Ceballos, Gerardo; Crist, Eileen; Diamond, Joan; Dirzo, Rodolfo; Ehrlich, Anne H.; Harte, John; Harte, Mary Ellen; Pyke, Graham; Raven, Peter H.; Ripple, William J.; Saltré, Frédérik; Turnbull, Christine; Wackernagel, Mathis; Blumstein, Daniel T. (2021)."Underestimating the Challenges of Avoiding a Ghastly Future".Frontiers in Conservation Science.1 615419.Bibcode:2021FrCS....1.5419B.doi:10.3389/fcosc.2020.615419.
^Lin, D; Hanscom, L; Murthy, A; Galli, A; Evans, M; Neill, E; Mancini, MS; Martindill, J; Medouar, F-Z; Huang, S; Wackernagel, M. (2018). "Ecological Footprint Accounting for Countries: Updates and Results of the National Footprint Accounts, 2012–2018".Resources.7(3): 58.https://doi.org/10.3390/resources7030058
How Earth's Population Exploded -Bloomberg Quicktake
