I grew up on quads in Northern Alberta (my parents would take me for rides as a baby to put me to sleep) - and up there a quad trail is very unintrusive on the ecosystem. The locations you can access you would never otherwise see unless you spent a week with a backpack or horse.
That being said, the population explosion down here seems to have made this necessary, so i'm not in disagreement with it. As Pipestoneflyguy said, the few always ruin it for the many. I guess the question that leaves me is this: if many areas are protected, that means less areas to quad - resulting in heavier traffic in said areas. This could have the potential to obliterate the ecosystems in those areas due to excessive overuse. Wonder how they decide where is ok to destroy, and where is not?
Glad its not my decision.