The fundamental reason why carbon dioxide in the atmosphere is critically important to biology is that there is so little of it. A field of corn growing in full sunlight in the middle of the day uses up all the carbon dioxide within a meter of the ground in about five minutes. If the air were not constantly stirred by convection currents and winds, the corn would stop growing.

A Many-colored Glass: Reflections on the Place of Life in the Universe (ed. University of Virginia Press, 2007) - ISBN: 9780813926636