Sorry I have difficulty finding the funny point here
Discussion
It's not a joke, not sure what your definition of green is
> Increased levels of carbon dioxide have helped boost green foliage across the world's arid regions over the past 30 years through a process called carbon dioxide fertilization, according to new research.
https://www.sciencedaily.com/releases/2013/07/130708103521.htm
Sustainable is what green means. Trees may get more food yes but doesn’t mean it is sustainable. Mars is full of CO2 if you want to define it as “greener” than earth then I don’t disagree with you in this aspect.