Sure, basic chemistry if plants extracted the C from CO2 we would end up with the same O2.  However as CO2 levels are rising that is not happening enough.<p>Of note, the current concentrations are 209 460 ppm of O2 compared with around 380 ppm of CO2.  So, it&#x27;s currently a non issue.  But again finite systems are finite.<p>PS: I only skimmed this as the first Google link: <a href="http:&#x2F;&#x2F;www.i-sis.org.uk&#x2F;O2DroppingFasterThanCO2Rising.php" rel="nofollow">http:&#x2F;&#x2F;www.i-sis.org.uk&#x2F;O2DroppingFasterThanCO2Rising.php</a>. No idea if it&#x27;s credable, so feel free to search.