What Disney film is this?

I watched this disney film once a long time ago but I cannot remember the title. It is about a human marking trees to be felled in the last forest in the amazon, and somehow he gets miniaturized by a fairy whom he befriends. At the same time, some kind of sludge/smoke monster that was trapped in an evil tree, gets loose and feeds on the smoke from the bulldozers and grows stronger. I don't really remember the ending, but it goes something like this. The monster grows powerful enough to destroy the forest, but the fairy flies into his mouth with a seed and is swallowed by the monster. The seed sprouts and begins to grow roots, branches and leaves and kills the monster. If anyone remembers this movie, could you please tell me soon? Thanks.