Verdun and The Somme were an ecological Diseaster. Look at this article: http://en.wikipedia.org/wiki/Zone_rouge_(First_World_War) and this one: http://en.wikipedia.org/wiki/French_villages_destroyed_in_the_First_World_War as well as this one: http://en.wikipedia.org/wiki/Battle_of_Verdun
I remember reading Alistair Horne's excellent book on Verdun, "The Price of Glory," and he says that there was something like a ton of explosive detonated for every square yard of the battlefield, rendering the soil to the consistency of fine sand.