Closed Ecology Experiments

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Closed Ecology Experiments


Closed ecology experiments refer to an ecosystem that has been established in a space that is isolated from outside influences. The ecosystem does not need externally supplied materials and does not exchange materials with the external environment. Instead, it is self-sustaining, with the living constituents providing the materials needed for the survival and growth of the community.

By establishing a self-contained ecosystem, the evaluation of a change in a target facet of the ecosystem (for example, temperature) on the functioning of the ecosystem as a whole can be assessed. This aim is more conjecture as of 2008. Most closed ecology experiments center around establishing an ecosystem that is stable, rather than trying to deliberately disrupt an existing system.

The best-known modern example of a closed ecology experiment is Biosphere 2, an enclosed environment over 3 acres in size that operated from the late 1980s to 2006. Biosphere 2 was an environmental experiment that sought to establish the viability of closed biospheres in future space colonies.

Closed ecology experiments are useful in modeling ecosystems on a local or global scale. For example, Biosphere 2 was used to explore the changes that occurred over time in the freshwater, marine water, desert, rain forest, and other environments that were part of the facility. As well, this closed ecology was a social experiment, which assessed the interactions of the volunteers who were enclosed in the facility for over two years.

Long-term space missions require smaller scale closed ecology experiments to assess the changes that could occur in the confines of a spacecraft during the multiyear voyage to planets such as Mars, and to minimize changes that would make life on board the ship uncomfortable or unhealthy. If properly done, the closed ecology system would provide the oxygen some food for the space flight or base.

Historical Background and Scientific Foundations

In a closed ecology experiment, the waste products produced by one or more species are used as nutrients by other species. In turn, the by-products can be utilized for survival and growth.

Most closed ecological systems are based on a phototrophic organism—an organism that derives its energy from sunlight. For example, green algae such as Chlorella are phototrophs; their use of sunlight as energy for growth enables them to produce oxygen, which can be used for the growth of other organisms in the closed ecosystem, potentially even humans. As well, the algae can be consumed directly as a source of food.

A closed ecology system usually also requires the presence of an autotroph, an organism that is able to produce carbon-based compounds from the energy available.

This sort of closed ecology system can be small in size. An example is a system abbreviated MELISSA (Micro-Ecological Life Support System Alternative). MELISSA was created by the European Space Agency with the goal of establishing a closed ecosystem that utilizes microorganisms and plants to provide life support for multi-year manned space flights or a base on the moon or other body. Wastewater, food remnants, and feces are utilized by bacteria for their growth. The bacterial by-products are in turn used as nutrients by the plants. The plant growth provides oxygen and food, and it can be used in water purification.

Other closed ecology experiments are much larger and complex. For example, during the 1970s in what was then the Soviet Union, a closed system called BIOS-3 that could house up to three people was used for experiments, the longest of which lasted 180 days.

The BIOS-3 facility, which was intended to develop an ecosystem that could be exploited for survival during long manned space flights, was approximately 11,000 square ft (1,022 square m) in area, and was divided into a number of compartments. One compartment housed a species of algae that produced the oxygen required by the personnel and for the growth of the plants housed in another compartment. The facility was not totally closed since the electrical power was provided by an off-site hydroelectric plant.

Biosphere 2, which is located north of Tucson, Arizona, was, when operational, the largest closed ecological facility ever constructed. The structure, which is two-and-a-half football fields in size, contained a rain forest, ocean complete with a coral reef, wetlands, grassland, and developed agricultural land. The facility’s name is an acknowledgment that Earth is the original biosphere.

Impacts and Issues

Large-scale closed ecological experiments such as BIOS-3 and Biosphere 2 allow environmental manipulations to be done without harming the environment outside of the facility. Although the intent at Biosphere 2 was to establish a stably functioning system, the potential exists to model some climatic conditions that are considered detrimental to assess their effect on other aspects of the closed system.


ATMOSPHERE: The air surrounding Earth, described as a series of layers of different characteristics. The atmosphere, composed mainly of nitrogen and oxygen with traces of carbon dioxide, water vapor, and other gases, acts as a buffer between Earth and the sun.

ECOSYSTEM: The community of individuals and the physical components of the environment in a certain area.

GAIA HYPOTHESIS: The hypothesis that Earth’s atmosphere, biosphere, and its living organisms behave as a single system striving to maintain a stability that is conductive to the existence of life.

Other closed ecology systems, such as MELISSA and Japan’s Closed Ecology Experiment Facilities, offer the potential to permit long-term space flights or the habitation of bases without the need to supply oxygen and food from Earth.

Although facilities such a BIOS-3 and Biosphere 2 have shown that a closed ecological system has the potential to be the organic center of life on a space ship, space base, or even a submarine, much work remains to be done to guarantee that the ecosystem will remain stable.

See Also Ecosystems; Greenhouse Effect



Allen, John. The Biospheres: A Memoir by the Inventor of Biosphere II. Santa Fe: Synergetic Press, 2008.

Lovelock, James. The Revenge of Gaia: Earth’s Climate Crisis and the Fate of Humanity. New York: Perseus Books, 2007.

Poynter, Jane. The Human Experiment: Two Years and Twenty Minutes Inside Biosphere 2. New York: Thunder’s Mouth Press, 2006.

Web Sites

University of Arizona. “Biosphere 2.” (accessed April 28, 2008).