Closed ecological system

{{short description|Ecosystem that does not exchange matter with the exterior}} [[Image:biosphere2 1.jpg|thumb|right|300px|Biosphere 2]]

'''Closed ecological systems''' or '''contained ecological systems''' ('''CES''') are ecosystems that do not rely on matter exchange with any part outside the system in order to help maintain life.

The term is most often used to describe small, man-made ecosystems. Such systems can potentially serve as a life-support system or space habitats.<ref>{{cite book | title=Manmade Closed Ecological Systems | author= I. I. Gitelson | author2= G. M. Lisovsky | author3= R. D. MacElroy | name-list-style= amp | publisher= Taylor & Francis |date=2003 | isbn = 0-415-29998-5}}</ref>

In a closed ecological system, any waste products produced by one species must be used by at least one other species. If the purpose is to maintain a life form, such as a mouse or a human, waste products such as carbon dioxide, feces, and urine must eventually be converted into oxygen, food, and water.

These systems still rely on constant external energy input, such as sunlight.<ref>{{Cite web |last=pakramer |date=2016-10-27 |title=The science of enclosed ecosystems |url=https://pakramer.com/2016/10/27/the-science-of-enclosed-ecosystems/ |access-date=2025-12-12 |website=P. A. Kramer |language=en}}</ref>

A closed ecological system must contain at least one autotrophic organism. While both chemotrophic and phototrophic organisms are plausible, almost all closed ecological systems to date are based on an autotroph such as green algae.

== Examples ==

A closed ecological system for an entire planet is called an ecosphere.<ref>{{cite web|url=http://www.cof.orst.edu/cof/fs/turner/pdfs/lexicon_of_the_spheres.pdf|title=A Lexicon of the Spheres|publisher=Oregon State University|access-date=2016-10-16|archive-url=https://web.archive.org/web/20161018011127/http://www.cof.orst.edu/cof/fs/turner/pdfs/lexicon_of_the_spheres.pdf|archive-date=2016-10-18|url-status=dead}}</ref><ref>{{cite web|url=http://www.sciencehelpdesk.com/unit/science2/11|title=ESO 2 Science 11: The Ecosphere and the Ecosystems|publisher=Science Helpdesk}}</ref>

Man-made closed ecological systems which were created to sustain human life include Biosphere 2, MELiSSA, and the BIOS-1, BIOS-2, and BIOS-3 projects.<ref>{{cite journal | journal=BioScience | date=Oct 1997 | volume=47 |issue=9 | pages=575–85 | title= Bios-3: Siberian experiments in bioregenerative life support | author=Salisbury FB | author2=Gitelson JI | author3=Lisovsky GM | doi=10.2307/1313164 | jstor=1313164 | pmid=11540303| doi-access=free }}</ref> However, no artificial closed ecological systems involving humans have been able to successfully support life for long periods of time.

Bottle gardens and aquarium ecospheres are partially or fully enclosed glass containers that are self-sustaining closed ecosystems that can be made or purchased. They can include tiny shrimp, algae, gravel, decorative shells, and ''Gorgonia''.<ref>{{cite web | url = http://www.ecospheres.co.uk/what-is-an-ecosphere/ | title=What is an EcoSphere? (Shrimp and Gorgonia coral)}}</ref>

== Weaknesses == Closed ecological systems often remain unstable due to low biodiversity, as they contain far less species than natural ecosystems. They also lack the redundancy that help stabilize natural cycles, trophic interactions, and population dynamics, as any decline in the species of the closed system may lead to system collapse as no other organisms are able to compensate.

Natural processes such as carbon sequestration and oxygen production are highly sensitive to changes within a closed system, which can lead to dangerous accumulations or depletions in gases and toxins. For example, in Biosphere 2, oxygen levels declined while soil microbes produced higher levels of carbon dioxide, which resulted in higher rates of algal blooms in water bodies. As a result, 30% of the species and all pollinators died off.<ref>{{Cite web |title=Biosphere 2: Why Did it Fail? |url=https://www.ryestrategy.com/blog/biosphere-2-learning-from-failure |access-date=2025-12-12 |website=RyeStrategy |language=en-US}}</ref>

Human involvement in closed systems create further weaknesses, as human respiration and nutritional diet are placed under additional strain.<ref>{{Cite web |last=pakramer |date=2016-10-27 |title=The science of enclosed ecosystems |url=https://pakramer.com/2016/10/27/the-science-of-enclosed-ecosystems/ |access-date=2025-12-12 |website=P. A. Kramer |language=en}}</ref> Micronutrient limitations, psychological needs, and waste production complicates the long-term overall stability of the system.

==In fiction==

Closed ecological systems are commonly featured in fiction and particularly in science fiction. These include domed cities, space stations and habitats on foreign planets or asteroids, cylindrical habitats (e.g. O'Neill cylinders), Dyson Spheres and so on.<ref>Westfahl, Gary (2005). "Space Habitats". The Greenwood Encyclopedia of Science Fiction and Fantasy: Themes, Works, and Wonders. Greenwood Publishing Group. pp. 736–737. ISBN 978-0-313-32952-4.</ref>

== See also == *{{annotated link|Biosphere}} *{{annotated link|Controlled ecological life-support system}} *{{annotated link|Controlled-environment agriculture}} *{{annotated link|IBTS Greenhouse}} *{{annotated link|Ecology}} *{{annotated link|Ecosphere (planetary)|Ecosphere}} *{{annotated link|Ecosystem services}} *{{annotated link|Eden Project}} *{{annotated link|MELiSSA}} *{{annotated link|Space colonization}} *{{annotated link|Spome}} *{{annotated link|Terraforming}} *{{annotated link|Chang'e 4}} *{{annotated link|Space stations and habitats in fiction}}

==References== {{reflist}}

Category:Ecological processes Category:Systems ecology Category:Ecosystems Category:Artificial ecosystems