Generalizing the entire mtn biking population(which is probably far greater than your weak enviromentalist clan, and remember, majority rules so resistance is futile) is pretty weak. Grow up and worry about something usefull. Again, how can I (we) believe anything you say when you are so far out of touch you resort to sweeping generalizations? What if I take a slick tire and ride through some cryptobiotic crust? I don’t think it would be much worse than a knobby tire.
Granted, the knobbies are usually wider, but to get that petty seems to be right up your alley. What are you talking about??? I said that knobby tires are very destructive. That’s just FACT. I didn’t say that you couldn’t do damage on other tires! ALL mountain biking is destructive, even on slicks. I am working on creating wildlife habitat that is off-limits to humans (“pure habitat”). Want to help? (I spent the previous 8 years fighting auto dependence and road construction.)