An excellent report entitled ,"Off Road To Ruin -How Motorized Recreation is Unraveling California's landscapes" was written by Teri Shore of the California Wilderness Coalition in 2001. This report has been praised by both the private sector and the BLM and Forest Service as a factual and accurate accounting of the issues relating to damage from ORVs. You are all encouraged to give it a read at the link below:
http://www.calwild.org/resources/pubs/fire.php