Originally published 20 June 1988
I have on my desk a clear glass sphere about three inches in diameter, on a plastic stand. The sphere is two-thirds filled with water. The remaining volume contains air. A snip of green algae, sea grass, floats in the water, and four tiny pink shrimp swim lazily about. The sphere is completely sealed. With the exception of heat and light, there are no transactions with the outside environment.
The sphere is an example of a closed ecosystem, a miniature world in which plants and animals live in balance with each other and all material resources and waste products are recycled.
The contents of the globe are not as simple as they appear. The shrimp and the sea grass are obvious, but these two species alone are not sufficient to sustain life in a sealed container. There are perhaps as many as a hundred species of life in the glass sphere, mostly microorganisms invisible to the eye.
The plants in the sphere make oxygen and food for the animals from sunlight, carbon dioxide, and inorganic chemicals. The animals breathe in the oxygen and expel carbon dioxide. They eat the plants and produce organic wastes. Bacteria oxidize the organic wastes and produce more carbon dioxide and inorganic chemicals.
The precise mix of organisms is crucial for the long-term success and beauty of the system. For example, ammonia is a waste product of the shrimp, but becomes poisonous in high concentrations. At least two kinds of bacteria are necessary to convert the ammonia into useful nitrite, thus keeping the nutrient and energy cycles going.
Space research
The glass-enclosed shrimp-algae ecosystem is based on NASA-supported research, and is made available to the public under a technology transfer by EcoSphere Associates of Tuscon, Arizona. It represents the end product of years of research in a field that is important for the conquest of space.
If humans are ever to establish permanent colonies on the moon or Mars, then closed-ecosystem research will show the way. The cost of transporting enough food, water, and oxygen from the Earth to sustain a space colony would be prohibitive. It will be more practical to provide the colony with the ingredients necessary for a self-sustaining, recyclable environment, similar to the one in my glass sphere.
Shrimp have stayed alive in closed shrimp-algae environments for as long as seven years. So far, this is a record for any of the higher forms of life.
A spectacular experiment involving humans in a closed ecosystem is in preparation near Tuscon, Arizona. The container for the experiment will be a multi-chambered, sealed glass building covering more than two acres of the Sonoran desert. Within the building scientists will create a variety of miniature environments — a rain forest, a savanna, a desert, a freshwater marsh, a saltwater marsh, and an ocean — each containing an appropriate mix of plants and animals, hundreds of species in all. Eight humans will attempt to live in the closed system for two years. There will be no material contact with the outside world.
This remarkable enterprise in the Arizona desert is the conception of a private company, Space Biospheres Ventures, and most of the $30 million price tag will be picked up by Texas oil billionaire Edward Bass. The name of the project is Biosphere 2. Of course, Biosphere 1 is the Earth itself.
The success or failure of their venture will teach us much about the feasibility of space colonies. Perhaps more importantly, the experiment will focus attention on present and future dangers to the biosphere of Earth.
Delicate balance needed
The Earth’s biosphere is roughly 10 trillion times more voluminous than the building in the desert that will house Biosphere 2. Research has shown that there is a direct relationship between the size of a closed ecosystem and its ability to sustain a balance of life. Nevertheless, it would be a mistake to imagine that the biosphere of Earth is so large as to be invulnerable. The clear-cutting of tropical forests, the unrestrained burning of fossil fuels, and nuclear war are examples of activities that can significantly alter the equation of matter and energy that has sustained life on Earth for nearly 4 billion years. Episodes of mass extinctions in the fossil record provide ample evidence that the equation can get wildly out of balance.
The glass sphere on my desk is a billion trillion times smaller than the biosphere of Earth, but it shares certain things with the larger system — water, air, and a balance of life. It is an Earth-like world I can hold in the palm of my hand. I will be watching the four tiny pink citizens of that world with a keen interest. Their fate could be our own.
The Biosphere 2 experiments achieved mixed success. The current research facility is now owned and operated by the University of Arizona. ‑Ed.
