Gaia: The Wisdom of the Earth
1991 Woodrow Wilson Biology Institute
The object of this activity is to introduce students to a controversial new theory that offers an explanation for the organization and function of the Earth. After completing this activity, students will be able to:
- describe, diagram, and give examples of homeostatic mechanisms in individual organisms, communities, ecosystems, and the biosphere.
- outline the Earth's history in terms of solar, geologic, and atmospheric evolution.
- describe organic evolution in terms of the relationships of organisms to each other and to the Biosphere.
- describe and give examples of how living things affect climate.
- prepare and interpret graphs that show changes in the Earth's temperature and atmospheric gases.
- describe and give examples of how human activity has affected the biosphere.
- apply homeostatic mechanisms to make predictions about the future of the Earth in terms of relationships between living things and components of the atmosphere.
- describe some controversies that surround the theory of Gaia. This should include scientific, social, and, if possible, religious and philosophical components.
- explain why Lovelock and Margulis are not concerned about whether life on Earth will continue. In other words, why they believe that Gaia will "survive" even if humans seriously damage to the environment.
The Gaia Theory, first proposed by British scientist James Lovelock in the early 1970's, is gaining an increasing number of advocates throughout the world's scientific community. In the United States, its most notable supporter is Dr. Lynn Margulis of the University of Massachusetts, whose explanation of the origin of eukaryotic cells through symbiotic relationships among prokaryotic organisms revolutionized evolutionary thought in the late 1960's. Gaian theory holds that the Earth can be described as a vast, autopoietic system of many components, all of which have evolved together to enhance and regulate conditions for the perpetuation of life.
Simple examples of how the Earth regulates itself include the maintaining an atmospheric oxygen level at close to 20 per cent for several hundred million years. If this level were to fluctuate to as high as 25 per cent, a single spark could ignite a conflagration that would sweep across the continent. If the oxygen level were 15 per cent or less, lighting a match would be impossible. Also, geologic evidence indicates that for the same length of time the salinity of the ocean has remained remarkably constant at somewhat less than 10 per cent of saturation. This is particularly remarkable because dissolved minerals have been transported by water toward oceans almost since Earth was formed. No satisfactory explanation has been advanced for this constancy, which affects all life on Earth.
The scientific community remains divided about the Gaia Theory. Many well-known scientists argue that since they know of no way to test Gaia scientifically, it is little more than a metaphor explaining phenomena that can be explained mechanistically. As more evidence becomes available, including recent work by Mazumder (1991), and Ramanathan (1991), the case for a Gaian regulation system becomes stronger. Scientists and science educators owe it to themselves to be informed about developments in the Gaian issues. Gaia is based upon true science. It provides opportunities for testing, predicting, and challenging established scientific thought at all academic and scientific levels. Also, it offers many ideas for scientific experimentation.
Terminology. The following terms are useful in understanding the nature of Gaian theory. It is suggested that teachers list them on the board and briefly discuss them with students to establish a setting for activities to follow.
- Albedo. This is the reflectivity of the Earth's atmosphere. It is increased by clouds and atmospheric particles, including those from combustion, dust storms, and volcanoes.
- "Goldilocks Phenomenon" . This is a simple way of stating that Venus is too hot for life to exist, Mars too cold, and Earth is just right.
- Greenhouse effect. The warming of the Earth due to the tendency of heat to be trapped within the lower levels of the atmosphere by atmospheric gases, including carbon dioxide, carbon monoxide, methane, and chlorofluorocarbons. Since human activity has increased the quantities of these gases in the atmosphere, there is concern that the temperature of the Earth in increasing. Theoretically, this could lead to vast disruptions of ecosystems, flooding of coastal areas because of the melting of polar icecaps, and desertification of previously productive areas.
- Homeostasis. This has been described by American physiologist Walter B. Cannon as the "wisdom of the body". It is the tendency of living things to sustain themselves by maintaining a dynamic equilibrium with the environment. Temperature regulation in mammals provides an excellent example of this: a mammal exposed to cold first perceives lowered temperature with sensory receptors in its skin. In short order, the central nervous system emits signals for peripheral blood vessels to contract, body hair to become erect, and muscle tissue to start shivering, thus increasing surface temperature. So in short order, the body increases its natural insulation and increases its metabolism.
- Oxygen - carbon dioxide cycling. This describes the uptake of carbon dioxide and production of oxygen by photosynthetic organisms, which when combined with the uptake of oxygen and production of carbon dioxide by respiration and burning, creates a cycle.
Since 900 A. D. the average temperature of the Earth has fluctuated around 15o C. The following data show the average fluctuations above or below 15o C per 50 years from 900 A. D. until 2000 A. D. (projected).
Make a graph of these data, with time on the horizontal axis and temperature on the vertical axis. On the vertical axis, write the numbers 14o C, 15o C, and 16o C, with at least 3 divisions between each degree (14.2o C, 14.4o C, etc). Discuss trends shown on the graph.
Show students the NOVA program, The Goddess of the Earth (1986). Discussion afterwards should include questions about the research of various scientists in the program, evidence for various scientific ideas, and attitudes different groups of people have toward Gaia.
Other audiovisual programs include the computer activity SimEarth, the Living Planet (Maxis, Inc., 1990), and Daisyworld, available through audiovisual supply companies.
Activities associated with Gaia include the construction and monitoring of environmental chambers containing plants and other organisms (including simple systems that can be enclosed in plastic bottles),
outdoor environmental monitoring and sampling, and population studies with simple organisms such as earthworms, planaria, and pill bugs. These activities can be adapted to a variety of grade levels.
There is no real way to conclude studies of Gaian systems, any more than there is a way to conclude the study of life in a biology class. It is a concept that lends itself to a class or to the curriculum of an entire school. The significance of its role in a school can be determined by teachers. Its importance in understanding the Earth is still emerging.
Eddy, John A. "Global Change: Where Are We? Where Are We Going?" Earthquest. Spring, 1991. Pp. 38-42.
Eddy, John A. "Global Changes of the Past," In Bradley, R. S., Ed. Global Changes of the Past.
Boulder: OIES, 1991.
Goddess of the Earth. NOVA program from WGBH, Boston. 60 minutes. 1986.
Greadel, T. E., and P. J. Crutzen. "The Changing Atmosphere." Readings from Scientific American. 1990.
Lovelock, James E. Gaia: A New Look at Life on Earth. Oxford University Press, 1972.
Lovelock, James E. The Ages of Gaia. New York: W. W. Norton. 1988.
Mann, Charles. "Lynn Margulis: Science's Unruly Earth Mother." Science, Vol. 252, April 19, 1991. Pp. 378-381.
Mazumba, Asit. "Ripple Effects." The Sciences. November/December, 1990. Pp. 38-42.
Mitchell, J. F. B. "The Greenhouse Effect and Climate Change." Reviews of Geophysics. Vol 27, 115-139.
Rowland, F. S., and I. S. A. Isakson, Eds. The Changing Atmosphere. New. York: John Wiley and Sons, 1988.
Stevens, William K. "An Oceanic Indication That Earth's Climate Might Regulate Itself." New York Times, Tuesday, May 7, 1991. P. B6.