It's an animated movie and i think it's Disney (but they having re-release it yet) where a guy is shrunk down by these fairies and he starts to fall in love with one of them (the main heroine). in one scene he carves a heart in the tree with his and her names in it however she get's angry at him and takes his hand and puts it on the tree asking if he could feel the Tree's pain because of what he did.
outside the forest there is this big logging machine operated by 2 men who i think they know the guy who was shrunk down. they cut down one particular tree that the fairies used to seal way some evil, after the three had been turn into planks this tar like goo secretes from it and moves around the place which is apparently the evil. it climbs to the top of the machine and put's it's mouth over the exhaust pipe and "drinks" the exhaust fumes commenting it's like "mother's milk" growing larger as if it gets stronger from pollution.
this evil then takes over the radio and posing as the men's boss redirect them to go to the fairies's home tree, when they get close the fairies and the shrunk guy fight back and stop the machine but then the evil takes over the machine starting it back up, growing insanely large and now looks like he's made from smoke, though i don't know what happens to it after that