A small freshwater fern bricked the Earth's climate for a while: https://en.wikipedia.org/wiki/Azolla_event https://en.wikipedia.org/wiki/Azolla_event It is po

A small freshwater fern bricked the Earth's climate for a while: https://en.wikipedia.org/wiki/Azolla_event https://en.wikipedia.org/wiki/Azolla_event It is possible that the evolution of a fungus that could degrade lignin is what brought about the end of the Carboniferous, with an associated extinction event: https://en.wikipedia.org/wiki/Carboniferous#Fungi https://en.wikipedia.org/wiki/Carboniferous#Fungi And, of course, probably the biggest one of the all, the Great Oxidation Event: https://en.wikipedia.org/wiki/Great_Oxidation_Event https://en.wikipedia.org/wiki/Great_Oxidation_Event // None of this is to downplay humanity's role in our current climate catastrophe. But we are the first of a long line of organisms that have the ability to do something about it, which is not nothing.