Testing the Effect of Life on Earth's Functioning: How Gaian Is the Earth System?
- 1.1k Downloads
The Gaia hypothesis of Lovelock states that life regulates Earth's functioning for its own benefit, maintaining habitable, or even optimum conditions for life. But what is beneficial? What is good for one species, may be bad for another. Problems associated with this important, but ill-defined hypothesis make it difficult to test. In order to address these problems and make the concept of Gaia testable, I give a precise definition of terms. Based on these definitions, I put forward four null hypotheses, describing increasing beneficial effects of life on the conditions of Earth, ranging from an ‘Antigaian’ to an ‘optimising Gaian’ null hypothesis. I list some indications for rejection of all but one hypothesis, and conclude that life has indeed a strong tendency to affect Earth in a way which enhances the overall benefit (that is, carbon uptake). However, this does not imply that the biota regulates Earth's environment for its own benefit.
KeywordsBeneficial Effect Null Hypothesis Optimum Condition Earth System Strong Tendency
Unable to display preview. Download preview PDF.
- Betts, R. A.: 1999, ‘Self-Beneficial Effects of Vegetation on Climate in an Ocean-Atmosphere General Circulation Model’, Geophys. Res. Lett. 26, 1457–1460.Google Scholar
- Fraedrich, K., Kleidon, A., and Lunkeit, F.: 1999, ‘A Green Planet versus a DesertWorld: Estimating the Effect of Vegetation Extremes on the Atmosphere’, J. Climate 12, 3156–3163.Google Scholar
- Kirchner, J. W.: 1989, ‘The Gaia Hypothesis: Can It Be Tested?’, Rev. Geophys. 27, 223–235.Google Scholar
- Kleidon, A., Fraedrich, K., and Heimann, M.: 2000, ‘A Green Planet versus a Desert World: Estimating the Maximum Effect of Vegetation on Land Surface Climate’, Clim. Change 44, 471–493.Google Scholar
- Kleidon, A. and Heimann, M.: 1998, ‘Optimised Rooting Depth and Its Impacts on the Simulated Climate of an Atmospheric General Circulation Model’, Geophys. Res. Lett. 25, 345–348.Google Scholar
- Lenton, T. M.: 1998, ‘Gaia and Natural Selection’, Nature 394, 439–447.Google Scholar
- Lovelock, J. E. and Margulis, L.: 1974, ‘Atmospheric Homeostasis by and for the Biosphere: The Gaia Hypothesis’, Tellus 26, 2–10.Google Scholar
- Lovelock, J. E.: 1989, ‘Geophysiology, the Science of Gaia’, Rev. Geophys. 27, 215–222.Google Scholar
- Roeckner, E., Arpe, K., Bengtsson, L., Christoph, M., Claussen, M., Dümenil, L., Esch, M., Giorgetta, M., Schlese, U., Schulzweida, U.: 1996, The Atmospheric General Circulation Model ECHAM-4: Model Description and Simulation of Present-Day Climate, Report 218, Max-Planck-Institut für Meteorologie, Hamburg, Germany, ISSN 0937-1060.Google Scholar
- Schneider, S. H.: 1987, ‘Gaia: A Goddess of the Earth?’, in 1988 Yearbook of Science and the Future, Encyclopaedia Britannica, Encyclopaedia Britannica Inc., Chicago, pp. 29–43.Google Scholar
- Schneider, S. H. and Boston, P. J. (eds.): 1991, Scientists on Gaia, MIT Press, Cambridge, Mass.Google Scholar
- Schrödinger, E.: 1944, What is Life? The Physical Aspect of the Living Cell, The University Press, Cambridge, U.K.Google Scholar
- Volk, T.: 1998, Gaia's Body: Toward a Physiology of Earth, Springer Verlag, New York. (Received 12 October 2000; in revised form 25 July 2001)Google Scholar