West Mojave Plan FEIR/S - Desert Managers Group

Although most of the above-average vehicle impacts are contained within BLM OpenAreas, similar vehicle impact areas were observed from California City, north through the RandMountains, into Fremont Valley. In effect, this is a heavy OHV use area affecting both privatelands around California City and about half of the region that is proposed for DWMAmanagement. Beginning in the late 1970’s and early 1980’s, extending through 2002, data frompermanent study plots indicate that tortoises decreased from about 72% to 93% in this region.Reduced Tortoise Numbers Attributed to OHV Impacts: The literature suggests thatOHV use has resulted in reduced tortoise numbers (National Ecology Research Center 1990,USFWS 1994b), including juveniles next to well-used dirt roads (USFWS 1994b). Berry (1996)found that tortoise populations decreased significantly with (a) increasing mileages of lineardisturbances associated with roads, trails, routes, and tracks (P