West Mojave Plan FEIR/S - Desert Managers Group

Given these observations, the only certain areas of MGS extirpation within the range arethose that have been physically developed. Such areas include, but are not limited to, pavedroads and parking lots; residential, commercial, and industrial sites occupied by buildings,graded areas, and other areas where vegetation has been mechanically removed; solar facilities atKramer Junction and Harper Lake; and large mined areas (U.S. Borax, Rand Mining Company,portions of the Shadow Mountains located east of Edwards AFB).Although urbanization and its affiliated impacts are prevalent in the Palmdale/Lancasterand Victorville/Apple Valley/Hesperia areas (Aardahl and Roush 1985), other communitieswithin the range (e.g., Ridgecrest, California City,.) are also likely affecting MGS habitats.Whereas the MGS has been observed at the edge f urbanization (e.g., Barstow, China Lake golfcourse), it is unlikely that the species can persist for long in urban settings (Laabs 1998).Potential causes for the likely extirpation of the MGS from Lucerne Valley have includedagricultural development (Laabs 1998) and the expansion of the California ground squirrel(Spermophilus beecheyi) in the area (Wessman 1977). The isolation of MGS in Lucerne Valleyfrom the main portion of its range, located west and north of the Victor Valley, has also beencited (Gustafson 1993).Uncertainties with the MGS That Do Not Affect the Desert Tortoise: There aresignificant differences, in terms of detectability and distribution, between the tortoise and theMGS that warrant brief mention.• Detectability: The tortoise leaves behind evidence (scats, burrows, tracks, carcasses,courtship rings) that allows for detection that is not available with the MGS. Tortoisecarcasses and fragments may persist for as many as 20 years, and still allow for positiveidentification. This is not true for the MGS. As such, it is relatively straightforward todetermine occupied (or recently occupied) tortoise habitat. MGS detection, by contrast,relies on either observing or trapping animals, or occasionally finding road-killedsquirrels. For these reasons, nothing comparable to the relatively accurate tortoise rangemap could be developed for the MGS without a focused trapping survey. Even the 1993range reduction (Gustafson 1993) was based more on anecdotal information than onsubstantiated absence of the MGS west of Highway 14, in the Antelope Valley.• Records: MGS records have been maintained for more than 100 years. This historicinformation is not available for the tortoise, for which records have only been availablesince the mid-1970s (except for anecdotal accounts). This is critically important, as itallows for a MGS range map that shows both historical and current distribution, eventhough current distribution cannot be fully ascertained based on available data. Giventhese data, it is possible to determine what percent of the known and historic range hasbeen converted to urban, agricultural, and other uses.• Current Distribution: It cannot be emphasized enough that the entire known range ofthe MGS occurs within the West Mojave; all but a small part of that, which is locatednortheast of Searles Dry Lake, occurs within the planning area, west and north of theMojave River. The tortoise occurs in four different states on millions of acres, whereasChapter 3 3-166