In January, the Minnesota chapter of America's powerful bird protection organisation, the National Audobon Society (NAS), adopted a resolution supporting wind development but cautioning that towers should be "user friendly" to birds. "The lattice towers seem to act as perches and nesting areas for raptors -- they almost invite bird activity," says Don Arnosti of the Minnesota Audubon Council. "If there are solid towers, that is not the case." But Sue Orloff of Biosystems Inc, who has studied the issue of bird kills and wind plant for two years for the California Energy Commission (CEC), vehemently disagrees. "Preliminary data indicate lattice [towers] may have a higher mortality rate, but we need more research," she says. "There is some indication that may be the case, but you can't say that yet."
Orloff says cause and effect has simply yet to be proven. She suggests that lattice towers could, for example, kill more birds if they operate more often than tubular tower machines. Orloff notes that preliminary data also indicate that a high tip speed may cause more bird kills, but again she stresses that cause and effect has yet to be proven. A current Biosystems study is probing the potential links, concentrating on 12 factors that were not isolated in previous studies, including tower type, tip speed and length of blade. It will be issued this autumn, she says.
Anecdotal evidence is that "whitewash" -- bird droppings -- can be seen more often on lattice towers than tubular ones, says Dick Anderson, staff biologist for the CEC. "But although there's intuition," he says, "there's no evidence that any type of turbine is more dangerous than another." He says the sample sizes are so small, that years of studies should be conducted. Jan Beyea, chief scientist of NAS, agrees that the jury is still out on lattice towers. "It's a prime hypothesis, but it's not proven," he says. "It's untested but reasonable. It's pretty clear that designs are going to have an impact." He also notes there is a tremendous lack of data. NAS has called for a moratorium on wind development in the migratory paths of birds, including the Altamont Pass in northern California. "There are different problems in different parts of the country," he says, noting that in the Midwest migration is not such an issue as it is in northern California or southern Spain.
A fundamental problem is there is not enough funding for studies, says the CEC's Anderson. Although the bird issue is crucial to the future of wind development, state and federal policy-makers do not see it as enough of a priority, especially at state level where the election year focus is on crime.
The industry, particularly Kenetech Windpower, is funding substantial studies, notes Anderson. Last month the company was not prepared to comment on the lattice tower issue. Kenetech, based in San Francisco, is the main manufacturer of lattice tower turbines. American trade magazine Wind Energy Weekly reports that in "a related story" to the NAS opinion on wind turbines, "Kenetech is using tubular towers for 33M-VS turbines being installed on Buffalo Ridge in Minnesota."