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Panel Discards Scientists' Recommendations on Wildlife Kills at Solar Plant

Solar flux field surrounds a power tower at Ivanpah | Photo: Craig Dietrich/Flickr/Creative Commons License

A task force charged with addressing the burgeoning issue of bird and bat deaths at the Ivanpah Solar Electric Generating System (ISEGS) has dismissed many of the recommendations in a report on the topic issued by the U.S. Fish and Wildlife Service's forensics lab, according to documents released by the California Energy Commission.

That report by USFWS's National Fish and Wildlife Forensics Laboratory, which ReWire reported on in April, suggested that actual levels of wildlife mortality and injuries at ISEGS are being obscured by inadequate surveys for injured and dead animals, and proposed several measures by which those surveys could be made more scientifically rigorous.

But according to minutes of a May 20 meeting of the ISEGS Avian & Bat Technical Advisory Committee (TAC), an interagency body convened to assess the wildlife mortality issue at the plant, members dismissed a number of apparently common-sense steps to increase the validity of carcass surveys -- and one likely method to sharply reduce injuries to birds during migration season.

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The TAC meeting, held in Nipton, California, included members Roger Johnson of the CEC, Larry LaPre from the Bureau of Land Management, Amedee Brickey of USFWS, Magdalena Rodriquez of the California Department of Fish and Wildlife, and Mitch Samuelian and Ray Kelly from ISEGS. The TAC was convened to address two main sources of mortality at ISEGS: burn injuries sustained when animals fly through the field of concentrated solar flux focused on the plant's three power towers by its tens of thousands of mirrored heliostats, and collisions with those heliostats by birds who apparently fail to recognize them as solid, impermeable surfaces.

Also in attendance were Brian Boroski and Dave Johnston of the ecological consulting firm H.T. Harvey & Associates. Boroski and Johnston spoke to TAC at some length about one way in which the committee has agreed to make carcass surveys at ISEGS more thorough: using specially trained dogs that will signal their handlers when they find dead birds or portions thereof.

But other recommendations designed to increase the accuracy of mortality surveys were dismissed, some with only cursory explanation in the minutes.

Among them was a recommendation that surveys be expanded to include areas outside the perimeter of the project. In the National Fish and Wildlife Forensics Laboratory report, justification for this recommendation took the form of a happenstance observation by USFWS investigators on site at ISEGS:

Forensic Lab staff observed a falcon or falcon-like bird with a plume of smoke arising from the tail as it passed through the flux field. Immediately after encountering the flux, the bird exhibited a controlled loss of stability and altitude but was able to cross the perimeter fence before landing. The bird could not be further located following a brief search... As demonstrated by the falcon, injured birds (particularly larger birds), may be ambulatory enough to glide or walk over the property line indicating a need to include adjacent land in carcass searches.

But at the meeting in Nipton, H.T. Harvey's representatives offered evidence that just under 95 percent of all birds found singed by exposure to solar flux were found within 260 meters, or just under 285 yards, from the power towers. That statistic was used as a reason to dismiss offsite surveys. In the words of the meeting minutes, that data "indicates a low probability of observing off-site singed carcasses through systematic ground surveys."

The possibility that offsite carcasses would be strongly weighted toward larger birds, raptors, and others, with sufficient momentum and wing surface area to carry them out of the perimeter, is not apparently addressed in the minutes. Nor is the possibility that mortality of these larger birds would have special conservation impact.

Also dismissed by the TAC were the Forensics Lab's recommendations that daily carcass surveys be performed around the bases of the towers, and that vegetation be cleared inside the fenceline to reduce the facility's attractiveness to predators that might either consume carcasses before they can be recorded, or even become casualties themselves. Both recommendations were dismissed by TAC with the note that "current data does not support implementing this measure."

So was the Forensics Lab's recommendation that ISEGS operations be suspended during peak bird migration periods.

One thing TAC did agree to was to ask H.T Harvey & Associates to step up its documentation of insect mortalities at ISEGS, as a way of determining whether the facility is attracting those insects, which in turn would attract birds who eat insects. Special mention was made of monarch butterflies, reported by USFWS to be a frequent apparent casualty at ISEGS. TAC directed H.T Harvey & Associates to look into the possibility that native milkweed growing on and near the site might be helping to attract monarchs, which USFWS's Brickey pointed out may themselves become a protected species in the future, given their population declines over the last decade or two.

The TAC will be meeting next in July, at which point it will discuss progress on the dog program and research into ways to dissuade birds from approaching the six square-mile plant.

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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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