Quote from : Nausicaä of the Valley of the Wind Movie

Nausicaä: Every one of us relies on water from the wells, because mankind has polluted all the lakes and rivers. but do you know why the well water is pure? It's because the trees of the wastelands purify it! And you plan to burn the trees down? You must not burn down the toxic jungle! You should have left the giant warrior beneath the earth!... Asbel, tell them how the jungle evolved and how the insects are gaurding it so we won't pollute the earth again. Asbel please!