Terry Hancock wrote: > "Plants consume CO2 and make O2" > > Well, yes, but they also consume O2, just like animals. *On balance*, > the statement is *usually* true. But most plants would probably > die in a pure-CO2 environment (unless they can drive the atmosphere > to a better composition fast enough).
Ha, finally one I can comment one with a reasonable level of confidence. On balance, plants consume CO2 and produce O2 *as long as they are growing*. You see, they use the C from the CO2 to build the material they are made of. Once they are full-grown, the amount of O2 produced by their photosynthesis is balanced by the amount of O2 consumed by their respiration; the same goes for the CO2 produced in consumed in both processes. This can be generalized to whole forests too. Often people think that the Amazon rain forests produce large quantities of O2, but that's just not true. During their initial growth, they indeed produced large quantities of O2. As long as they stay the same size (the same amount of biomass actually), there is no net effect. Now that large areas are burnt to make place for roads and agriculture, the CO2 comes back in the atmosphere while O2 from the atmosphere is consumed in the flames. It's very well possible that this is a simplification that glosses over a few details such as other sources of carbon, but in general it's good enough. -- If I have been able to see further, it was only because I stood on the shoulders of giants. -- Isaac Newton Roel Schroeven -- http://mail.python.org/mailman/listinfo/python-list
