Impact...oof, this is a tough one. The real problem with impact is we ain't seen nothing yet. The impact on the canyons that we see today (aside from the massive bovine factor) is minimal compared with what we'll seen in the next many years as hordes of people seek the wilder, less tamed country.
I think probably the most stark realization for me was doing deep creek. The banks of the stream were incredibly lush with vegetation, seemingly quite pristine. Then vanished sharply, altogether, right at the junction with the virgin. The contrast was stunning and i assumed only one explanation.
if it's our right to be in these canyons, it's everyone's right. canyons will be discovered, whether any particular group of individuals likes it or not. it's simply a matter of time. keeping canyons a secret only protects them in the short term, for the experiences of a very limited number of people.
if you want land protected in the long term, you need force people to be very conservative about everything they do out there. this seems amazingly tough. we HAVE improved camping impact in the past years....kinda, i found a bunch of backpacker dehydrated food packages burnt and left at a campsite in west canyon. but walking impact??!! how on earth are we going to control that without well defined trails or brainwashing? we still have problems with trampling cyanocryptogamobiotic soilcrust.
i am all for preserving as much as possible, but i don't see how massive impact is not inevitable. However, I do wish to be convinced otherwise!!