Editing Carrying capacity (section)

{{Short description|Maximum population size of a species that an ecosystem can support}}
{{distinguish|Biocapacity}}
The '''carrying capacity''' of an [[ecosystem]] is the maximum population size of a biological [[species]] that can be sustained by that specific environment, given the food, [[habitat]], [[Drinking water|water]], and other [[resource]]s available. The carrying capacity is defined as the [[Environment (biophysical)|environment]]'s maximal load,{{clarify|date=February 2024}} which in [[population ecology]] corresponds to the population equilibrium, when the number of deaths in a population equals the number of births (as well as immigration and emigration). Carrying capacity of the environment implies that the resources extraction is not above the rate of regeneration of the resources and the wastes generated are within the assimilating capacity of the environment. The effect of carrying capacity on [[population dynamics]] is modelled with a [[logistic function]]. Carrying capacity is applied to the maximum population an environment can support in [[ecology]], [[agriculture]] and [[Fishery|fisheries]]. The term carrying capacity had been applied to a few different processes in the past before finally being applied to [[human population]] limits in the 1950s.<ref name="Chapman-2018">{{cite journal |last1=Chapman |first1=Eric J. |last2=Byron |first2=Carrie J. |title=The flexible application of carrying capacity in ecology |journal=Global Ecology and Conservation |date=January 2018 |volume=13 |pages=e00365 |doi=10.1016/j.gecco.2017.e00365 |doi-access=free |bibcode=2018GEcoC..1300365C }}</ref> The notion of carrying capacity for humans is covered by the notion of [[sustainable population]].

An early detailed examination of global limits on human population was published in the 1972 book ''[[Limits to Growth]]'', which has prompted follow-up commentary and analysis, including much criticism.<ref>Turner, Graham (2008) [http://www.csiro.au/files/files/plje.pdf "A comparison of ''The Limits to Growth'' with thirty years of reality"] {{webarchive|url=https://web.archive.org/web/20101128151523/http://www.csiro.au/files/files/plje.pdf|date=28 November 2010}} Commonwealth Scientific and Industrial Research Organisation ([[CSIRO]]) Sustainable Ecosystems.</ref> A 2012 review in the journal ''[[Nature (journal)|Nature]]'' by 22 international researchers expressed concerns that the Earth may be "approaching a state shift" in which the [[biosphere]] may become less hospitable to human life, and in which the human carrying capacity may diminish.<ref>{{cite journal|last1=Barnosky|first1=AD|last2=Hadly|first2=EA|display-authors=etal|year=2012|title=Approaching a state shift in Earth's biosphere|journal=Nature|volume=486|issue=7401|pages=52–58|bibcode=2012Natur.486...52B|doi=10.1038/nature11018|pmid=22678279|hdl-access=free|s2cid=4788164|hdl=10261/55208}}</ref> This concern that humanity may be passing beyond "[[tipping point]]s" for safe use of the biosphere has increased in subsequent years.<ref>{{Cite journal |last1=Armstrong McKay |first1=David I. |last2=Staal |first2=Arie |last3=Abrams |first3=Jesse F. |last4=Winkelmann |first4=Ricarda |last5=Sakschewski |first5=Boris |last6=Loriani |first6=Sina |last7=Fetzer |first7=Ingo |last8=Cornell |first8=Sarah E. |last9=Rockström |first9=Johan |last10=Lenton |first10=Timothy M. |date=2022-09-09 |title=Exceeding 1.5°C global warming could trigger multiple climate tipping points |url=https://www.science.org/doi/10.1126/science.abn7950 |journal=Science |language=en |volume=377 |issue=6611 |pages=eabn7950 |doi=10.1126/science.abn7950 |pmid=36074831 |hdl=10871/131584 |s2cid=252161375 |issn=0036-8075|hdl-access=free }}</ref><ref name="Bradshaw-2021">{{Cite journal |last1=Bradshaw |first1=Corey J. A. |last2=Ehrlich |first2=Paul R. |last3=Beattie |first3=Andrew |last4=Ceballos |first4=Gerardo |last5=Crist |first5=Eileen |last6=Diamond |first6=Joan |last7=Dirzo |first7=Rodolfo |last8=Ehrlich |first8=Anne H. |last9=Harte |first9=John |last10=Harte |first10=Mary Ellen |last11=Pyke |first11=Graham |last12=Raven |first12=Peter H. |last13=Ripple |first13=William J. |last14=Saltré |first14=Frédérik |last15=Turnbull |first15=Christine |date=2021-01-13 |title=Underestimating the Challenges of Avoiding a Ghastly Future |journal=Frontiers in Conservation Science |volume=1 |pages=615419 |doi=10.3389/fcosc.2020.615419 |issn=2673-611X|doi-access=free |bibcode=2021FrCS....1.5419B }}</ref> Although the global population has [[Day of Eight Billion|now passed 8 billion]], recent estimates of Earth's carrying capacity run from two to four billion people, depending on how optimistic researchers are about the prospects for international cooperation to solve problems requiring collective action.<ref>Examples include Lianos, T. P., & Pseiridis, A. (2016). Sustainable welfare and optimum population size. ''Environment, Development and Sustainability'', ''18''(6), 1679-1699; Tucker, C. K. (2019). ''A Planet of 3 Billion: Mapping Humanity's Long History of Ecological Destruction and Finding Our Way to a Resilient Future: a Global Citizen's Guide to Saving the Planet''. Atlas Observatory Press; Dasgupta, P. (2019). ''Time and the generations: population ethics for a diminishing planet''. Columbia University Press; Tamburino, L., & Bravo, G. (2021). Reconciling a positive ecological balance with human development: A quantitative assessment. ''Ecological Indicators'', ''129'', 107973.</ref>