As long as we have enough trees and plants... We can still breathe. Worst case, the planet becomes inhabitable and by that time we have an intergalactic war over "paradise" level planets. However, most of us will be likely dead by that time, so...
English
-
I would think that even with all of these plants and trees, bacteria or underwater flora would provide the Earth more oxygen than anything else. I mean, some flora do grow underwater and Earth is 70% (iirc) ocean.