Really, 4 wheelers don't do nearly as much damage as the US Army has done on non military land all over Alaska.  For example, Shaw Creek Flats is totally scarred from maneuvers the Army ran there in the winter in the 60's.  The Army used bulldozers to rip trails and make air strips.  You can still see them with Google Earth.  Look just south of the Caribou-Shaw Creek junction to see an air strip.  I don't hear any complaints about this!