Nature's Fury

Destroy all creatures.
Then if {g}{g} was spent to cast this spell, forests
you control become 1/2 treefolk creatures. They're
still lands. If {w}{w} was spent to cast this spell look at the top 4 cards of your library, you may put a green or white creature from among them into your hand.
The few survivors can tell you that concrete and steel
gave way to the water and wind of the storm long
before the roots of the trees.