I think that fungus is an realy impornt to the ecosystems because the fungus eats and live off the the dieing or died origames like roting trees and old loge so fungus is good because it eat up the deads
Lichens i think they can do this because they need water and they can tell if it is good of not becauseif they have a lot of bad water they no that there is something in the air like hight aic raine in the air