News and analysis about renewable energy in California.

Solar Project Would Destroy Half of Rare Plant's Population in California

Gravel milkvetch, Astragalus sabulonum | Photo © James M. Andre

The Hidden Hills Solar Electric Generating System, proposed by BrightSource Energy for the Pahrump Valley in Inyo County, would destroy half the known occurrences of a rare plant in California, according to the California Native Plant Society (CNPS) -- and the California Energy Commission (CEC) isn't doing enough to make sure that loss of population won't result in the plant's extinction in the state, says the group.

The gravel milk-vetch, Astragalus sabulonum, is known from just eight spots in the state, all of them in the Pahrump Valley.

Four of those occurrences would be wiped out by the Hidden Hills project as it's currently designed, says CNPS.

The charges by CNPS came in the form of a protest letter sent to the CEC on February 4 by the CNPS's Conservation Program Director Greg Suba. In the letter, Suba charges that BrightSource's current mitigation plan for protecting milkvetch populations that remain are insufficient to keep the species in California:

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As described in the FSA [Final Staff Assessment]... there are eight reliably certain occurrences of ASSA [gravel milk-vetch] documented in California. Four of these will be destroyed by project impacts -- 50 percent of the occurrences. There are four remaining off-site occurrences in CA, all of which occur on lands where the plant's habitat faces continued degradation over time from a high percent cover of weedy, invasive plant species, impacts from off-road vehicle activity, and other stressors.... [O]nly 2 of the 8 California occurrences of ASSA will be placed in conservation status as mitigation, while 4 of the 8 occurrences will be destroyed. [F]or every 2 occurrences of ASSA lost onsite (4 total), only 1 occurrence will be protected offsite through mitigation (2 total). This "kill 2 : save 1" ratio of mitigation does not bode well for the species.

CNPS is urging the Energy Commission to require all remaining populations of the gravel milk-vetch be protected.

The gravel milk-vetch is a low-growing annual herbaceous plant in the bean family, with compound leaves covered in thick gray hairs. It puts out purple flowers in spring when the previous wet season has delivered between 4 and 12 inches of rain.

Another Astragalus species, the Nye milk-vetch (Astragalus nyensis), also turns out to have its only California occurrences in the vicinity of the Hidden Hills plant. The area is home to more than 90 other special-status plant species.

The Hidden Hills project, proposed for 3,277 acres of private land, would incorporate hundreds of thousands of mirrored heliostats surrounding two 750-foot power towers. If completed, it would generate a maximum of 500 megawatts of power during the day.

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About the Author

Chris Clarke is a natural history writer and environmental journalist currently at work on a book about the Joshua tree. He lives in Joshua Tree.
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