What are the conditions happening in certain countries that could upset or disturb the oxygen cycle?
A. Probably the leading investigator of the global oxygen cycle is Dr. Ralph Keeling of Scripps Institution of Oceanography. The web link (http://earth.agu.org/revgeophys/keelin01/keelin01.html) provides information on his work. Given that oxygen is produced by vegetation, it might be argued that mankind has the greatest influence on the oxygen cycle by means of alterations in the world’s vegetation (e.g., deforestation, effects of increasing atmospheric CO2 on photosynthesis).