The chemical disequilibrium of the Earth's atmosphere is the feature that first captured Lovelock's attention. He noticed that on Venus and Mars (planets apparently with no life at least on the surface) the atmospheres are primarily CO2. On Earth, the dominant constituents are reactive species of nitrogen, oxygen, and minor constituents (methane, ammonia, nitrous oxide, etc.). In the absence of other factors, over time, one would predict that Earth would resemble her neighbor planets but she does not. According to Gaia, life is the factor that maintains this disequilibrium over time. Table 1 shows various
Table 1 Proposed Gaian-controlled parameters
• Temperature, gas balance, greenhouse feedback
• Plant-albedo feedback (e.g., Daisyworld-like mechanisms)
• Evapotranspiration, latent heat, climate feedback
• Photosynthetic manipulation of air composition
• Dimethyl sulfide (DMS), marine cloud, algae association
• Microbial respiration rates and the carbon cycle
• Methanogenesis and greenhouse warming
• Carbon dioxide levels and carbonate cycle
• Carbonate-shelled organisms as long-term carbon sink
• Continental weathering rates via lichen, other microorganisms, etc.
• Oxygen levels, biomass burning feedback
• Ocean salinity levels parameters that have been suggested as possibly Gaia-controlled. The chemical compounds involved and their various reactions and fluxes control the large-scale bio-geochemical cycles that enable Earth to constantly recycle materials and make them available for succeeding generations of life.
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