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This suggests to technological optimists that new technological discoveries (or the deployment of existing ones) could continue to increase Earth's human carrying capacity, as it has in the past.<ref>{{Cite book |last=Simon |first=Julian Lincoln |url=https://www.worldcat.org/oclc/7177304 |title=The ultimate resource |date=1981 |publisher=Princeton University Press |isbn=0-691-09389-X |location=Princeton, N.J. |oclc=7177304}}</ref> Yet technology has unexpected side effects, as we have seen with stratospheric ozone depletion, excessive nitrogen deposition in the world's rivers and bays, and global climate change.<ref name="MEA-2005" /><ref name="Bradshaw-2021" /> This suggests that 8 billion people may be sustainable for a few generations, but not over the long term, and the term ‘carrying capacity’ implies a population that is sustainable indefinitely. It is possible, too, that efforts to anticipate and manage the impacts of powerful new technologies, or to divide up the efforts needed to keep global ecological impacts within sustainable bounds among more than 200 nations all pursuing their own self-interest, may prove too complicated to achieve over the long haul.<ref>{{Cite book |last=Mark. |first=Gardiner, Stephen |url=http://worldcat.org/oclc/753470941 |title=A perfect moral storm : understanding the ethical tragedy of climate change |date=2011 |publisher=Oxford University Press |isbn=978-0-19-537944-0 |oclc=753470941}}</ref>
As aforementioned, oneOne issue with applying carrying capacity to any species is that ecosystems are not constant and change over time, therefore changing the resources available. Research has shown that sometimes the presence of human populations can increase local [[biodiversity]], demonstrating that human habitation does not always lead to deforestation and decreased biodiversity. Another issue to consider when applying carrying capacity, especially to humans, is that measuring food resources is arbitrary. This is due to choosing what to consider (e.g., whether or not to include plants that are not available every year), how to classify what is considered (e.g., classifying edible plants that are not usually eaten as food resources or not), and determining if [[Calorie|caloric values]] or [[Nutritional value|nutritional values]] are privileged. Additional layers to this for humans are their cultural differences in taste (e.g., some consume flying termites) and individual choices on what to invest their labor into (e.g., fishing vs. farming), both of which vary over time. This leads to the need to determine whether or not to include all food resources or only those the population considered will consume. Carrying capacity measurements over large areas also assumes [[Homogeneity and heterogeneity|homogeneity]] in the resources available but this does not account for how resources and access to them can greatly vary within regions and populations. They also assume that the populations in the region only rely on that region’s resources even though humans exchange resources with others from other regions and there are few, if any, isolated populations. Variations in [[Standard of living|standards of living]] which directly impact resource consumption are also not taken into account. These issues show that while there are limits to resources, a more complex model of how humans interact with their ecosystem needs to be used to understand them.<ref>{{Cite journal |last=Cliggett |first=Lisa |date=2001 |title=Carrying Capacity's New Guise: Folk Models for Public Debate and Longitudinal Study of Environmental Change |url=http://dx.doi.org/10.1353/at.2001.0003 |journal=Africa Today |volume=48 |issue=1 |pages=3–19 |doi=10.1353/at.2001.0003 |issn=1527-1978}}</ref> ▼Two things can be confidently asserted regarding Earth's carrying capacity, based on the Great Acceleration of energy and materials use, waste generation, and ecological degradation post-WW II.<ref>{{Cite book |last1=McNeill |first1=J. R. |url=http://dx.doi.org/10.2307/j.ctvjf9wcc |title=The Great Acceleration |last2=Engelke |first2=Peter |date=2016-04-04 |publisher=Harvard University Press |doi=10.2307/j.ctvjf9wcc |isbn=978-0-674-97073-1|s2cid=265214537 }}</ref> First, expansions in human carrying capacity have come at the expense of many other species occupying Earth today.<ref name="IPBES-2019" /><ref>Diaz, Sandra, et al. (2019). Pervasive human-driven decline of life on Earth points to the need for transformative change. ''Science'', 366, 1327.</ref> Between 1970 and today, populations of wild vertebrates have declined 60%;<ref>World Wildlife Fund. (2020). ''Living planet report 2020 - Bending the curve of biodiversity loss.'' WWF</ref> similarly sharp declines may have occurred among insects and vascular plants,<ref>Antonelli, A., Fry, C., Smith, R. J., Simmonds, M. S. J., Kersey, P. J., Pritchard, H. W., et al. (2020). ''State of the World’s Plants and Fungi 2020.'' Kew: Royal Botanic Gardens</ref> although the evidence is sketchier. So our successful efforts to increase human carrying capacity have come at the expense of Earth's capacity to sustain other species.<ref name="Crist-2017" /> As we have converted habitat and resources to our own use, other species have sharply declined—to the extent that conservation biologists speak of an incipient mass species extinction.<ref>{{Cite journal |last1=Cafaro |first1=Philip |last2=Hansson |first2=Pernilla |last3=Götmark |first3=Frank |date=2022 |title=Overpopulation is a major cause of biodiversity loss and smaller human populations are necessary to preserve what is left |url=http://dx.doi.org/10.1016/j.biocon.2022.109646 |journal=Biological Conservation |volume=272 |pages=109646 |doi=10.1016/j.biocon.2022.109646 |bibcode=2022BCons.27209646C |s2cid=250185617 |issn=0006-3207}}</ref>
Second, expansions in per capita wealth and the concomitant increases in per capita consumption, resource use and waste generation, tend to decrease the total number of people that can be sustained, long term.<ref name="Pimentel-1994" /><ref>Tucker, Christopher (2019) ''A Planet of 3 Billion.'' Atlas Observatory Press, Washington, DC, USA</ref> All else being equal, a richer population, living more luxuriously, has a lower carrying capacity than a poorer, more abstemious population.<ref name="Dasgupta-2019" /> As affluence goes up, population must come down to remain within any theoretical carrying capacity, and vice versa.<ref>{{Cite journal |last1=Lianos |first1=Theodore P. |last2=Pseiridis |first2=Anastasia |date=2015-09-19 |title=Sustainable welfare and optimum population size |url=http://dx.doi.org/10.1007/s10668-015-9711-5 |journal=Environment, Development and Sustainability |volume=18 |issue=6 |pages=1679–1699 |doi=10.1007/s10668-015-9711-5 |s2cid=154771905 |issn=1387-585X}}</ref>
▲As aforementioned, one issue with applying carrying capacity to any species is that ecosystems are not constant and change over time, therefore changing the resources available. Research has shown that sometimes the presence of human populations can increase local [[biodiversity]], demonstrating that human habitation does not always lead to deforestation and decreased biodiversity. Another issue to consider when applying carrying capacity, especially to humans, is that measuring food resources is arbitrary. This is due to choosing what to consider (e.g., whether or not to include plants that are not available every year), how to classify what is considered (e.g., classifying edible plants that are not usually eaten as food resources or not), and determining if [[Calorie|caloric values]] or [[Nutritional value|nutritional values]] are privileged. Additional layers to this for humans are their cultural differences in taste (e.g., some consume flying termites) and individual choices on what to invest their labor into (e.g., fishing vs. farming), both of which vary over time. This leads to the need to determine whether or not to include all food resources or only those the population considered will consume. Carrying capacity measurements over large areas also assumes [[Homogeneity and heterogeneity|homogeneity]] in the resources available but this does not account for how resources and access to them can greatly vary within regions and populations. They also assume that the populations in the region only rely on that region’s resources even though humans exchange resources with others from other regions and there are few, if any, isolated populations. Variations in [[Standard of living|standards of living]] which directly impact resource consumption are also not taken into account. These issues show that while there are limits to resources, a more complex model of how humans interact with their ecosystem needs to be used to understand them.<ref>{{Cite journal |last=Cliggett |first=Lisa |date=2001 |title=Carrying Capacity's New Guise: Folk Models for Public Debate and Longitudinal Study of Environmental Change |url=http://dx.doi.org/10.1353/at.2001.0003 |journal=Africa Today |volume=48 |issue=1 |pages=3–19 |doi=10.1353/at.2001.0003 |issn=1527-1978}}</ref>
== Recent warnings that humanity may have exceeded earth's carrying capacity ==
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