Agency: Mojave Solar Project Would Harm Tortoises

Desert Tortoise | Photo: USFWS/Flickr/Creative Commons License

The nation's chief wildlife protection agency is opposing a new solar project in the Ivanpah Valley just outside the California state line, saying the project as currently designed would harm the valley's beleaguered tortoise population. The US Fish and Wildlife Service has called for the BLM to either deny or redraw the proposed 350-megawatt Silver State South solar project, which would affect more than 13,000 acres of prime tortoise habitat adjacent to the California state line, a few miles north of the Mojave National Preserve.

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The Fish and Wildlife Service's (FWS) objections were made in a formal comment filed late last year in response to a draft Supplemental Environmental Impact Statement for Silver State South, released by the Bureau of Land Management (BLM). The project, proposed by the Tempe, Arizona-based firm First Solar, would directly occupy between 2,500 and 3,800 acres of land stretching from the California line to the northern edge of the Lucy Gray Mountains.

FWS's objections arise from the fact that the proposal occupies much of a north-south corridor of suitable habitat for the desert tortoise, which -- like the project's proposed footprint -- runs in a relatively narrow band between the Lucy Grays and Ivanpah Dry Lake to the west:

We are concerned about habitat fragmentation and demographic and genetic isolation of desert tortoise populations within the Ivanpah Valley and recommend that BLM select the 'No Action' alternative. Maintaining a robust population of desert tortoises within the Ivanpah Valley area is of particular importance because the habitat is already highly fragmented. Currently, the desert tortoise population within the Ivanpah Valley is only tenuously connected to the Ivanpah Critical Habitat Unit. This valley is a critical link between desert tortoise conservation areas in California and Nevada. Only four potential linkages remain in Ivanpah Valley. The linkage between the Silver State North project and the Lucy Gray Mountains is the widest of these linkages and likely the most reliable for continued population connectivity.

Tortoises don't migrate to find mates. Therefore, in order to provide adequate connectivity between populations of tortoises, says the FWS, corridors must be at least the width of a typical tortoise's lifetime range, allowing enough tortoises to have adjoining or overlapping ranges. FWS calculates that average range width at 1.4 miles, meaning that a functional corridor ought to be no narrower than that.

The BLM's draft EIS includes three variations on the project's footprint, and one "No Action" alternative in which no project would be built. The least extensive alternative would constrict the available tortoise habitat corridor to just under one mile: the BLM's Preferred Alternative would leave only 100 feet of habitat at the project's narrowest chokepoint.

The FWS's comments thus ask the BLM to either deny the project by adopting the No Action alternative, or send it back to the drawing board:

We recommend BLM select the 'No Action' alternative to avoid reducing the width of the existing corridor. If this is not possible, we ask BLM to minimize impacts to the linkage by creating and selecting a new alternative that would protect a corridor of undisturbed desert tortoise habitat between the Silver State North project and the Lucy Gray Mountains. This corridor should be wide enough to accommodate multiple desert tortoise ranges, spanning up to several times the desert tortoise lifetime utilization area.

The Silver State North project is a 50-megawatt solar facility built by First Solar and sold to the Canadian firm Enbridge in early 2012. It was completed in Ocrtober 2012 and is now generating power. Despite the projects' respective names, Silver State North would actually be surrounded on three sides by Silver State South.

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