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Know the West

More desert tortoises found at Mojave solar project


On Friday, April 15, the Bureau of Land Management issued a notice ordering the “immediate temporary suspension of activities” for part of the Ivanpah Solar Electric Generating Station construction site in the Mojave Desert (see HCN story “High Noon,” May 9, 2009). The reason: More desert tortoises, a federally threatened species, have been found in the proposed development area than official surveys anticipated.

Way more.

The Biological Opinion submitted by U.S. Fish and Wildlife in October 2010 estimated that up to 32 tortoises Mojave desert tortoisemight live in the 5.4-square mile site, which lies just west of the California-Nevada state line near the Mojave National Preserve. It allowed for 38 tortoises to be “captured and harassed” during project construction and for three to be killed in any one year throughout the project’s 40 years of operation. Biologists got to work last fall digging tortoises out and collapsing empty burrows, relocating the creatures to nearby pens in which they’d wait out the winter.

But by late March of this year, the biologists roaming the site had already turned up 39 adult tortoises. Two animals had already been killed – one by overheating as it paced along an exclusion fence, trying to find a way back to its ancestral home.

The discovery “indicates that there are more tortoises on the site than indicated in the biological opinion,” says Brian Croft, senior biologist with U.S. Fish and Wildlife in Ventura, Calif. "We’re reassessing the project and writing a new one.”

The news comes as no surprise to Michael Connor of the Western Watersheds Project, whose organization filed suit in January against the Interior Department, alleging hasty and inadequate analysis of the project’s environmental impacts.

“We told them repeatedly that they needed to do a better estimate and better count of the tortoises,” Connor says. Instead, Fish and Wildlife’s biological opinion took what Connor calls a “lowball” tortoise population number from official surveys provided by the Oakland, Calif.-based developer, BrightSource Energy. BrightSource biologists found 25 tortoises on the site in 2007 and 2008. BrightSource later reduced the project’s footprint.

Since tortoises spend more than half of the year underground, counting them requires more than an above-ground count, says Connor. Tortoises are often referred to as a "cryptic" species, which, in zoology, is a term referring to an animal's ability to camouflage and conceal itself to avoid detection.  Cryptic animals are hard to find, and harder to count.

Connor advocates a counting method that includes a “mark recapture,” in which biologists find tortoises and mark them in some way, and then return later for another survey.

By some estimates, the tortoise population on the site might be as high as 140. “That’s the upper confidence limit of the population estimate,” Croft says.  “But anytime you’re dealing with a cryptic species like tortoises your confidence estimates are really wide. The smaller size classes of tortoises are really hard to find, even for incredibly experienced (researchers).”

BrightSource spokesperson Keely Wachs has said that the temporary suspension won’t delay the 2013 start of the project. The suspension order doesn’t affect ongoing work on Phase I, where the tortoises have already been cleared.

Nature and the federal agencies tasked with protecting it on public land, however, may have the final say.

“If we look at it and decide that there are too many tortoises on the site we could conceivably call jeopardy,” Croft says. “But we can’t be pre-decisional or give any inkling of what we want to do." (If the FWS did determine the species was in jeopardy, it would halt the project and potentially force the developers to make significant changes to the generating station.)

“We are trying to do it as quickly as possible,” he adds, if not for the developer’s sake, then for the tortoises themselves. “We have some tortoises in quarantine pens from Phase I already. We don’t want to just leave them there."

Judith Lewis Mernit is a contributing editor at High Country News.

Image of desert tortoise courtesy Flickr user Mike Jones.