The Wildlife Professional

Legend Transmission Lines*

735kV - 999kV 500kV - 734kV 345kV - 499kV 230kV - 344kV Belo w 230kV

Direct Normal Solar Radiation

kWh/m2/day Greater than 8.00 7.75 - 8.00 7.50 - 7.75 7. 25 - 7.50 7.00 - 7. 25 6.75 - 7.00 6.50 - 6.75 6. 25 - 6.50 6.00 - 6. 25 5.75 - 6.00 5.50 - 5.75 Less than 5.50

*Source: POWERmap, powermap.platts.com ©2007 Platts, A Division of The McGraw-Hill Companies The direct normal solar resource estimates shown are derived from 10 km SUNY data, with modifications by NREL.

Credit: Department of energy’s National renewable energy Laboratory

in the western United states, the sun’s most intense radiation bakes parts of the Mojave Desert in California, Nevada, and Arizona, fertile ground for solar development. in those three states alone, permit applications for solar power projects on public land cover more than two million acres.

plants will tend to be sited near existing power lines that march across the desert. If that’s the case, the solar facilities could form extensive barriers to wildlife movements and gene flow. There is evidence that the isolation of desert bighorn sheep populations by interstate highways, for example, has led to rapid loss of genetic diversity (Epps et al. 2005). Further loss of connectivity due to the barriers posed by large solar projects, which are typically surrounded by fencing, could adversely affect a variety of wildlife species, including those that depend on isolated dune systems (Murphy et al. 2006).

Loss of vegetation. Parabolic trough facilities employ long rows of curved mirrors to concentrate solar heat. These require precise orientation to the sun on relatively level ground, so the sites are typically cleared of all vegetation. Though other solar technologies do not necessarily require complete clearance, leveling, and grading, much of the natural vegetative cover must nevertheless be removed or modified to prevent fire danger and allow for the placement of solar collectors, roads, and other improvements. The solar collectors themselves may shade a large proportion of each site, affecting remaining vegetation. Therefore, not only will desert plant life be lost, but so will some of the creatures that depend on it

for food, water, shade, and shelter from predators. “All solar technologies have the potential to contribute to significant habitat loss and fragmentation,” says Jody Fraser, a biologist with the U.S. Fish and Wildlife Service (FWS) in Carlsbad, California.

Water loss. Concentrating solar power (CSP) facilities that generate electricity using thermal heat typically require groundwater for energy generation, cooling of condensers, and washing mirrors and other components. By some accounts, CSP generation can require more than a million gallons per megawatt per year. Pumping large amounts of water out of desert aquifers can impact nearby wetlands or riparian areas by reducing water availability. In addition, desert washes may have to be re-routed and channelized to control flooding hazards at many potential solar sites. The water demands of large-scale, wet-cooled solar technologies could have serious implications for rare desert creatures like the tiny Devil’s Hole pupfish (Cyprinodon diabolis), which lives only in an aquifer-fed pool in the Amargosa Desert of Nevada, an area now slated for large solar projects.

Taking Action: A Case Study Few would dispute the value of conserving desert biodiversity or of developing clean, renewable energy. The challenge is learning how to reconcile these often conflicting goals. Desert tortoises offer a case study on what stakeholders can do to meet this challenge. The Mojave population of the desert tortoise has been federally listed as threatened since 1990. Consequently, FWS developed a recovery plan that was published in 1994, long before Big Solar emerged as an issue. FWS and its Nevada-based Desert Tortoise Recovery Office (DTRO) are now working with numerous stakeholders to complete a new Revised Recovery Plan (FWS 2008), which considers some potential impacts from large-scale desert development.

Those impacts could be severe for the elusive desert tortoise, which spends up to 95 percent of its life in underground burrows to escape the desert’s heat and cold. The animals eat wildflowers, grasses, and cacti—the source of most of their water—and require roughly 100 acres of habitat per adult. With low reproductive rates, threats from desert development and long-term drought, and predation from ravens and coyotes, desert tortoises are in decline. It’s clear that the tortoises “are going downhill virtually throughout their range,” says biologist Peter Woodman. Solar facilities could add a significant threat,