Varstivus

Just imagine them being carted around in giant flower pots by Druids.

They get eaten by caterpillars.

Dryads essentially get a 'freebe' when there's a world change. They are allowed to move their tree to an appropriate location in the new map with no problems, or questions asked. Normally, however, a tree would have to die, and its Amber Seed (I think that's what it's called) moved and replanted, though this can only happen once.