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The lifetime of plants is 95% complete.

  1. Apr 7, 2008 #1
    This is an interesting statistic I read recently... apparently, in 500 million years the atmospheric CO2 will have been vastly depleted due to it reacting with silicon and being stored underground. The CO2 levels will then be too low to allow photosynthesis to occur. This statistic, presumably does not take into account the human impact on CO2 levels… perhaps global warming is not so bad after all.
  2. jcsd
  3. Apr 7, 2008 #2

    jim mcnamara

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    Staff: Mentor

    Could you cite your source?

    I'm just guessing: the authors are assuming no more atmospheric outgassing from volcanoes. Why 500 million years?

    Without more to go on this sounds like pure speculation....
  4. Apr 7, 2008 #3
    it would be nice if you could support such a statement with a reference.

    For instance here is something about the long carbon cycle.


    Indeed CO2 is depleting from the atmosphere due to chemical reactions with silicates forming limestones but these limestones are decomposed by volcanic activity bringing CO2 back into the atmosphere. The question would indeed be if this process is in dynamic equilibrium or at which concentration the CO2 would decrease in equilibrium.

    Estimates for that may be based on the assumption that CO2 was much higher in the geologic past. Recent research however suggests that these past levels may be lower than always assumed. For instance Royer 2003 See fig 3 on page 8, suggesting that the CO2 level during the last 60-70 million years was comparable to nowadays around 300-400 ppmv.

    But in the end the avaiable carbon in the carbon cycle is directly related to the possible total size of the biomass.
  5. Apr 7, 2008 #4
    I can't recall the exact title of the book but it was something like "Autobiography of earth" or "Earth story"...

    I'll finds out later on and post it up. It's deffinatley worth a read.
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