West Mojave Plan FEIR/S - Desert Managers Group

Rand Mountain area were highest close to open routes. Open routes may induce negativeimpacts for substantial distances; even at 500-feet from an open route, unauthorized tracks wereobserved at a rate of almost one per 20 linear foot.Negative effects on the desert environment have been summarized (National EcologyResearch Center 1990, USFWS 1994b). Impacts include damage to and loss of habitat (Jennings1997a, USFWS 2002) and severe declines in biomass of plants and vertebrates (USFWS 1994b).Both annual and perennial plants are affected (Jennings 1997a, National Ecology ResearchCenter 1990), which in turn affect forage quality, water availability, and thermoregulation(USFWS 1994b).Vollmer et al. (1976) reported that cross-country OHV travel impaired annual plantproductivity, retarded shrub regrowth, resulted in less plant cover and density, and conspicuouslydecreased shrub biomass. In comparing areas of different disturbance levels, Webb et al. (1983)concluded that light OHV use might not cause the severity of impact that occurs in some ghosttowns, but OHV pit areas have more soil and vegetation disruption than naturally recoveringghost towns. Berry (1996) indicated that OHV use directly affects plants and animals bydisrupting the distribution, composition, structure, diversity, and biomass of animal and plantcommunities; changing the watershed; and promoting desertification.The USFWS (2002) concluded that unauthorized activities, particularly OHV use, havedegraded desert tortoise habitat. The access provided by the BLM for legitimate uses, such asrecreation, facilitates some degree of unauthorized use (USFWS 2002). In addition tounauthorized roads and trails, areas that are frequently used for loading and unloading vehiclescan be severely degraded (USFWS 2002).Habitat Regeneration: Vollmer et al. (1976), upon revisiting their study plot 18 monthsafter the tests were conducted, found that little damage to shrubs was apparent from a distance,but that when viewed from nearby, tracks were clearly discernible. They concluded that trucktracks can persist at least 10 to 12 years depending on the substrate, and that shrub cover may bere-established within a couple of decades if there is no further damage. National EcologyResearch Center (1990) estimated full-recovery time required to ameliorate severe OHV impactsshould probably be estimated in terms of human life spans; and that hundreds or thousands ofyears may be necessary for disturbed areas to recover. Stowe (1988) found that many of theolder, smaller trails that were identified 1977-78 appeared to be unused in 1988, and in somecases the vegetation appeared to be growing back over the edges of the trails.OHV Impacts to Wash Habitats: Jennings (1993, 1997a) found that vehicles’ driving inwashes disturbed relatively rare species of plants that were restricted to washes. LaRue (1997)found catclaw acacia and desert willow mostly restricted to washes in the Ord Mountain area.Damage observed in the Ord Mountains included disturbed soil and terrain, crushed shrubs, anderoded margins of washes, which led to widening of the washes. He found that some routes inwashes became impassable when banks and boulders were encountered, which necessitatedturning around and resulted in new shrub damage.Chapter 3 3-126