West Mojave Plan FEIR/S - Desert Managers Group

were observed in the 294 mi 2 Johnson Valley open area. Five were in higher sign count areasand five were outside. None was found in the 22 mi 2 higher density area southeast of the Ord-Rodman DWMA, where a recent die-off was detected. This may suggest that tortoises wereonce relatively more common than they are now (i.e., as evidenced by the prevalence ofcarcasses).One measure is to divide the tortoise encounter rate by the carcass encounter rate. Thisratio is 1.2 for Stoddard Valley, 2.5 for Spangler Hills, and 8.2 for Johnson Valley. The sameratio for the DWMAs is: 1.8 for Ord-Rodman, and 4.5 for Superior-Cronese and 7.0 forFremont-Kramer. The lower ratios for Stoddard Valley, Ord-Rodman, and Spangler Hills (1.2,1.8, and 2.5, respectively) coincide with regions of relatively more tortoise encounters comparedto carcasses (excepting Spangler Hills, where both were less commonly found). This comparesto the higher ratios for Superior-Cronese, Fremont-Kramer, and Johnson Valley (4.5, 7.0, and8.2, respectively) where there were relatively fewer tortoise encounters compared to carcasses.Dr. Berry documented a 77% decline between 1980 and 1994 on the Johnson Valleystudy plot, which is within the open area. All other such declines have occurred in the Fremont-Kramer and Superior-Cronese DWMAs. The two study plots showing the smallest declines wereLucerne Valley (i.e., 30% decreases between 1980 and 1994) and Stoddard Valley (5% between1981 and 1991). These data suggest that there may be a differential die-off in Johnson Valleythat is more similar to Fremont-Kramer and Superior-Cronese DWMAs than in Stoddard Valleyand Ord-Mountain areas.Relative Occurrence of Vehicle Impact Areas: Map 3-14 shows the spatial distributionof three types of vehicle impact areas that occur within the planning area: BLM open areas,heavy OHV use areas, and residential areas. Rules of polygon establishment describedelsewhere were used to delineate these regions 18 . Importantly, only above-average vehicleimpact data collected during sign count surveys (1998-2002) were used in polygonestablishment. Although these types of impacts occur throughout many portions of the planningarea not encompassed in the polygons, the identified regions (and data discussed herein) reflectthe most severe and intense levels of vehicle impacts on lands where human uses are mostconcentrated (i.e., on at least four contiguous square miles where every square mile had aboveaverageimpacts).Open areas are designated by the BLM for vehicle free play, and occur in seven specificareas. Residential impact areas occur in three general regions: west and northwest of thecommunity of Silver Lakes, north of Hinkley, and in the “Coyote Corner,” southwest of FortIrwin. Heavy OHV Use areas are as disturbed as designated open areas, but are not officiallydesignated for this form of vehicle use. The impact area between California City and the RandMountains is not a BLM open area, but it is very large and, in places, as impacted as open areas.Interestingly, there is also a 14 mi 2 area (i.e. East Sierra in Table 3-26) seven to eight miles north18As in other similar calculations, although Map 3-14 shows the distributions of the larger polygons, only the squaremiles of data are included in the table and discussed in the text. Importantly, all data describe above-average vehicleimpacts; there are individual square miles of similar disturbance and many other square miles affected by belowaverageimpacts; these areas are significantly affected by vehicle impacts.Chapter 3 3-130