During the Carboniferous period, which was between 299 to 359 million years ago, the earth was covered in swamps. Enormous trees grew out of these swamps. Like modern trees, the first trees absorbed carbon from the atmosphere in exchange for oxygen. Since the first trees were so much larger than modern trees, there existed much more oxygen and much less carbon in the atmosphere during the carboniferous period compared to today.
The first trees appeared around 390 million years ago. For 150 million years, these trees piled up on the ground’s surface after they died, as there were no wood-digesting organisms in existence at the time. This meant that trees at the time were not converted into atmospheric carbon. Over the course of natural history, all of these dead trees hardened and eventually formed into coal, which is the same coal that we use today. Termites eventually arrived and started cleaning up the various forms of dead plant matter and trees that had littered the ground. This removal of dead plant matter, allowed the earth’s soil to become fertile enough to sprout a plethora of different plant species. In addition to that, termites also maintain the proper ratio of carbon and oxygen in the atmosphere by converting dead trees and plant matter into atmospheric carbon.
During the carboniferous period insects did exist, but much like the enormous trees, insects were also huge. High oxygen levels required animals at the time to have relatively large tracheas that could accommodate excess amounts of oxygen. Around 260 million years ago, the first cellulose-eating organisms appeared. The trees that had not yet been turned into coal were digested by these organisms, which released carbon back into the air. This increase in carbon caused oxygen levels to drop. This oxygen decrease caused trees and insects to shrink to the sizes that we see today.
Somewhere between 200 and 250 million years ago, termites evolved from wood-eating cockroaches to become the most significant recyclers of trees and plant matter on earth. Much like wood-digestion, termite-farmed fungus also work to break down plant matter in order convert it to carbon. The original pre-termite fungal organisms that degraded plant matter likely died out or decreased in prevalence once termites took over. If termites were to disappear today, trees and plant matter would collect on the ground, which would not only dramatically decrease the amount of vegetation on earth, but termites could no longer convert trees and plant matter into carbon. This would cause oxygen levels to rise again, and humans would probably die off long before the gigantic bugs returned.
Do you think that other forms of cellulose-degrading organisms would evolve to take the place of termites if termites were to disappear?