Well, you're basically increasing their food supply. So yes, that does promote plant growth. The "CO2 causes global warming" hysteria was always exactly just that. It always relied on shoddy models that don't even remotely properly reflect climate on Earth. It's true that it can cause smog in large cities or industrial centers, though. But if the ecoterrorists really want to "protect" the planet, then they should look elsewhere. Like how many Asian countries literally use rivers as replacements for landfills, causing tons of plastic to drift into the oceans every year.