A report just made public by the U.S. Fish and Wildlife Service documents a disturbing amount of bird injuries at three large California desert solar power plants, and says that there are no easy fixes to the issue.
The report, compiled by the USFWS's National Fish and Wildlife Forensics Laboratory, describes the results of examinations of 233 carcasses of birds found at the Ivanpah Solar Electric Generating System (ISEGS) south of Las Vegas, the Desert Sunlight facility near Joshua Tree National Park, and the Genesis Solar project west of Blythe in Riverside County.
The occasionally gruesome report indicates that injuries from concentrated solar flux and from impact with mirrors or photovoltaic panels constitute the two largest solar facility threats to wild birds, and suggests that the limited scope of carcass surveys at solar projects may be obscuring the true magnitude of bird mortalities they cause.
ISEGS is a 392-megawatt concentrating solar power tower facility operated by NRG Energy for partners BrightSource Energy and Google. NextEra Energy Resources owns both the Genesis Solar project, a 250-megawatt parabolic trough concentrating solar project, and Desert Sunlight, a 550-megawatt photovoltaic project being built by First Solar. The report thus examines one of each of the main technology types used in large desert solar projects.
Of the bird carcasses studied, significantly more than half came from one project: 141 out of the 233 carcasses examined by the National Fish and Wildlife Forensics Laboratory team came from ISEGS. Two thirds of the remainder, or 61, came from Desert Sunlight, with 31 provided by the operators of the Genesis Solar project.
Those proportions may or may not represent each project's relative risk to wildlife: the majority of the carcasses provided were "incidental" finds, discovered as workers were performing other tasks. And it's worth noting that the number of birds examined from Genesis Solar totaled less than half the number of carcasses project owner NextEra told the CEC it found on the site in August 2013.
But taking the numbers at face value, the report's authors conclude that Desert Sunlight may pose the greatest risk of the three projects to water birds, and that ISEGS, the only project of the three to use solar power tower technology, constitutes a unique threat to wildlife due to the highly concentrated solar energy -- "solar flux" -- around its boilers.
A third cause of death among the birds studied, predation by other animals, likely results from birds having been injured or stranded at the facilities by solar flux, impact trauma, or other injuries, where opportunistic meat-eaters such as ravens, coyotes, or desert kit foxes then take advantage of the easy prey.
The ISEGS solar flux portion of the National Fish and Wildlife Forensics Lab report is notably striking, even distressing. 47 of the 141 bird carcasses provided the lab by ISEGS showed clear signs of solar flux injury, with feather damage ranging from singeing to charring, and a few instances of skin burns.
Also distressing, though for different reasons: the authors mention that ISEGS' owners have failed to provide them with information on the project's solar flux operating temperatures "despite repeated requests," forcing them to compile data from other sources.
One bird not examined by the lab, but which the authors cite as evidence that current carcass search strategies may be woefully inadequate, was a bird of prey that flew through the zone of solar flux at ISEGS during an October inspection by USFWS :
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.
Damage to feathers that impedes flight generally means the bird in question can't feed, escape predators, or regulate its body temperature, say the authors.
One other description of the scene at ISEGS during that October visit is especially chilling, and confirms ReWire's speculation that ISEGS may function as a huge "ecological trap" endangering an entiire food chain:
OLE [USFWS Office of Law Enforcement staff] observed large numbers of insect carcasses throughout the Ivanpah site during their visit. In some places there were hundreds upon hundreds of butterflies (including monarchs, Danaus plexippus) and dragonfly carcasses. Some showed singeing, and many appeared to have just fallen from the sky. Careful observation with binoculars showed the insects were active in the bright area around the boiler at the top of the tower. It was deduced that the solar flux creates such a bright light that it is brighter than the surrounding daylight. Insects were attracted to the light and could be seen actively flying the height of the tower. Birds were also observed feeding on the insects. At times birds flew into the solar flux and ignited.
The authors suggest that ISEGS and other proposed power tower facilities may have a "significant impact on monarch populations in the desert southwest."
The report also offers a bit of grisly jargon used by ISEGS workers to describe the effect of the solar flux on wildlife that flies into it:
Ivanpah employees and OLE staff noticed that close to the periphery of the tower and within the reflected solar field area, streams of smoke rise when an object crosses the solar flux fields aimed at the tower. Ivanpah employees used the term "streamers" to characterize this occurrence.
When OLE staff visited the Ivanpah Solar plant, we observed many streamer events. It is claimed that these events represent the combustion of loose debris, or insects. Although some of the events are likely that, there were instances in which the amount of smoke produced by the ignition could only be explained by a larger flammable biomass such as a bird. Indeed OLE staff observed birds entering the solar flux and igniting, consequently becoming a streamer.
OLE staff observed an average of one streamer event every two minutes.
The authors recommend a number of measures at the different facilities to lessen mortalities, including netting off evaporation ponds at Desert Sunlight to discourage water birds from landing there. Also suggested: clearing all vegetation inside the fenceline at Ivanpah to reduce the attractiveness of the site to predators, who might be attracted to the presence of disabled birds and themselves fall prey to solar flux injures or other harms.
The report may well have ramifications beyond the three power plants examined: the California Energy Commission will soon be considering whether to proceed with the Palen Solar Electric Generating System, a much larger version of Ivanpah proposed for the Chuckwalla Valley in Riverside County. That project's backers have agreed to provide avian mortality data from Ivanpah to use as a way to assess Palen's likely damage to wildlife, a main concern of the CEC's when it proposed to deny the project late last year.