So I think I should work on a chart to go into depth here.
Like:
Rainforest – 2′ ravaging radius, leaves all Verdant.
Verdant, Grasslands, forest, cavern teeming with life, or other large life forms in the radius – 5′ ravaging radius, leaves land drained, removes HP from other large lifeforms.
Rocky, desert, or Drained – 10′ ravaging radius, leaves all barren.
Barren – comes from the casters HP.
How does that look?