Owner tells the story of green houses dedicated to "tropical succulents." Yunno - those plants which grow best in tropical rain forests and for which any other growing situation is "challenged."
To make it easy for the plants, the greenhouses are flooded with CO2 and there are signs on the doors "No Enter - Insufficient Oxygen to Support Life - SCBA Required."
So it is very obvious that an increase in atmospheric carbon dioxide results in easier and better growing plants.
And (Owner thinks) probably is the "CO2 control mechanism" inherent in the design of the earth.
I wish there were more proof of this...
Dobbin