While doing some research on how Cacti & Succulents avoid the damaging photorespiration cycle during the absence of water, I came across the attached article relating to the increase in CO2 levels during drought. The NOAA study quoted was based on the 2002 absence of rainfall, which covered a widespread area.

As all gardeners know, if plants don't receive water, they will eventually die. Without H2O, they can't process CO2 and generate energy, while emitting Oxygen from the water as a waste product. They can also go into a destructive cycle, photorespiration, where they fix Oxygen, which provides no energy, but they then emit CO2, which further adds to the dilemma.

A bit of trivia to cheer up your day? :Rb

Here is a link that might be useful: Drought Exacerbates Carbon Dioxide Problem