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IMPACTS OF WIND ENERGY DEVELOPMENT ON WILDLIFE JANUARY 2004
(Note: In general, Department guidelines for all commercial/industrial-sized wind energy development projects would also include the Department's Trenching and Powerline Guidelines, as well as the standard New Mexico Wildlife of Concern county list. Most of the following recommendations were developed by the U.S. Fish and Wildlife Service and published as "Interim Guidance on Avoiding and Minimizing Wildlife Impacts from Wind Turbines". Federal Register: July 10, 2003. Volume 68, Number 132.)
Background Although wind-generated electrical energy is environmentally friendly in that it does not create air-polluting and climate-modifying emissions, wind turbines, particularly in the large arrays needed for commercial electricity generation, can have significant impacts on wildlife and wildlife habitats. These impacts include: • Habitat fragmentation from access roads, tower pads, above-ground powerlines and trenching for underground power lines. One mile of 16-foot wide road removes two acres of habitat. • Direct killing can occur to bats and birds, particularly raptors, from striking moving blades. When birds approach spinning turbine blades, a phenomena called "motion smear" occurs, which is caused by the inability of the bird's retina to process high speed motion stimulation. This occurs primarily at the tips of the blades, making the blades deceptively transparent at high velocities. This increases the likelihood that a bird will fly through this arc, be struck by a blade and be killed (Hodos et al. 2001). • Wind generator towers over 200 feet tall with lighting on top for aircraft avoidance can be assumed to potentially have some of the same effects on night-flying migratory birds as tall communications towers, with birds striking moving blades rather than guy-wires. For a description of effects of tall towers with lights on night-flying migratory birds, with specific lighting recommendations for wind generators, refer to Turbine Design and Operation Recommendations (below) or NMGF 2003 Tower Guidelines . • Raptors can be electrocuted on associated powerlines if raptor-safe technology is not used. Refer to Trenching and Powerline Guidelines. • Noise and visual disturbance can occur to sensitive species such as the Lesser Prairie Chicken, which rely on auditory communication for reproductive efforts and avoid vertical objects on the horizon, presumably due to the potential occurrence of predators such as hawks. • Documented mortalities indicate that bats are susceptible to being killed by wind turbines (Adams 2003). Although this does not appear at this time to be as much of a problem as it may be for birds, adverse impacts should be considered for migrating groups of bats or for local populations, due in part to the low reproductive rates of bats.
Site Development Recommendations (From USFWS Interim Guidance on Avoiding and Minimizing Wildlife Impacts from Wind Turbines)• Avoid placing turbines in documented locations of any species of wildlife, fish or plant protected under the Federal Endangered Species Act. • Avoid locating turbines in known local bird migration pathways or in areas where birds are highly concentrated, unless mortality risk is low (e.g., birds present rarely enter the rotor-swept area). Examples of high concentration areas for birds are wetlands, State or Federal refuges, private duck clubs, staging areas, rookeries, leks, roosts, riparian areas along streams, and landfills. Avoid known daily movement flyways (e.g., between roosting and feeding areas) and areas with a high incidence of fog, mist, low cloud ceilings, and low visibility. • Avoid placing turbines near known bat hibernation, breeding, and maternity/nursery colonies, in migration corridors, or in flight paths between colonies and feeding areas. • Configure turbine locations to avoid areas or features of the landscape known to attract raptors (hawks, falcons, eagles, owls). For example, Golden Eagles, hawks, and falcons use cliff/rim edges extensively; setbacks from these edges may reduce mortality. Other examples include not locating turbines in a saddle or pass in a ridge, or in or near prairie dog colonies. • Configure turbine arrays to avoid potential avian mortality where feasible. For example, group turbines rather than spreading them widely, and orient rows of turbines parallel to known bird movements, thereby decreasing the potential for bird strikes. Implement appropriate storm water management practices that do not create attractions for birds, and maintain contiguous habitat for area-sensitive species (e.g., Lesser Prairie Chicken). • Avoid fragmenting large, contiguous tracts of wildlife habitat. Where practical, place turbines on lands already altered or cultivated, and away from areas of intact and healthy native habitats. If not practical, select fragmented or degraded habitats over relatively intact areas. • Avoid placing turbines in habitat known to be occupied by Lesser Prairie Chickens or other species that exhibit extreme avoidance of vertical features and/or structural habitat fragmentation. In known Lesser Prairie Chicken habitat, avoid placing turbines within 5 miles of known leks (communal pair formation grounds). • Minimize roads, fences, and other infrastructure. • Develop a habitat restoration plan for proposed sites that avoids or minimizes negative impacts on vulnerable wildlife while maintaining or enhancing habitat values for other species. For example, avoid attracting high densities of prey animals (rodents, rabbits, etc.) used by raptors. • Reduce availability of carrion by practicing responsible animal husbandry (removing carcasses, fencing out cattle, etc.) to avoid attracting Golden Eagles and other raptors. • Post-development mortality studies should be a part of any site development plan in order to determine if or to what extent mortality occurs. Turbine Design and Operation Recommendations (From USFWS Interim Guidance on Avoiding and Minimizing Wildlife Impacts from Wind Turbines).• Use tubular supports with pointed tops rather than lattice supports to minimize bird perching and nesting opportunities. Avoid placing external ladders and platforms on tubular towers to minimize perching and nesting. Avoid use of guy wires for turbine or meteorological tower support. All existing guy wires should be marked with recommended bird deterrent devices (Avian Power Line Interaction Committee 1994). • If taller turbines (top of the rotor-swept area is >199 feet above ground level)) require lights for aviation safety, the minimum amount of pilot warning and obstruction avoidance lighting specified by the Federal Aviation Administration (FAA) should be used (FAA 2000). Unless otherwise requested by the FAA, only white strobe lights should be used at night, and these should be the minimum number, minimum intensity, and minimum number of flashes per minute (longest duration between flashes) allowable by the FAA. Solid red or pulsating red incandescent lights should not be used, as they appear to attract night-migrating birds at a much higher rate than white strobe lights. • Where the height of the rotor-swept area produces a high risk for wildlife, adjust tower height where feasible to reduce the risk of strikes. • Where feasible, place electric power lines underground (see trenching guidelines) or on the surface as insulated, shielded wire to avoid electrocution of birds. Use recommendations of the Avian Power Lines Interaction Committee (1994, 1996) for any required above-ground lines, transformers or conductors. • High seasonal concentrations of birds may cause problems in some areas. If, however, power generation is critical in these areas, an average of three years monitoring data (e.g., acoustic, radar, infrared, or observational) should be collected and used to determine peak use dates for specific sites. Where feasible, turbines should be shut down during periods when birds are highly concentrated at those sites. • When upgrading or retrofitting turbines, follow the above guidelines as closely as possible. If studies indicate high mortality at specific older turbines, retrofitting or relocating is highly recommended.
Background The problem in the U.S. surfaced in the late 1980s and early 1990s at the Altamont Pass Wind Resource Area, a facility then containing some 6,500 turbines on 73 mi² of gently rolling hills just east of San Francisco Bay, California (Davis 1995). Orloff and Flannery (1992) estimated that several hundred raptors were killed each year due to turbines collisions, guy wires strikes, and electrocutions. The most common fatalities were those of Red-tailed Hawks (Buteo jamaicensis ), American Kestrels (Falco sparvarius ) and Golden Eagles (Aquila chrysaetos), with fewer mortalities of Turkey Vultures (Cathartes aura), Common Ravens (Corvus corax), and Barn Owls (Tyto alba). The Altamont turbines are still estimated to kill 40-60 subadult and adult Golden Eagles each year, as well as several hundred Red-tailed Hawks and American Kestrels. Of the variety of wind turbines at the site, the smaller, faster moving, Kenetech-built, lattice-supported turbines caused most of the mortality. As part of a re-powering effort, these turbines are now being replaced with slower moving, tubular-supported turbines. While Europeans have used tubular towers almost exclusively, the U.S. has almost solely used lattice support, at least until recently (Berg 1996).
Low wind speed turbine technology requires much larger rotors, blade tips often extending more than 420 ft. above ground, and blade tips can reach speeds in excess of 200 mph under windy conditions (J. Cadogan, U.S. Department of Energy, 2002, per. comm.). When birds approach spinning turbine blades "motion smear" - the inability of the bird's retina to process high speed motion - occurs primarily at the tips of the blades, making the blades deceptively transparent at high velocities. This increases the likelihood that a bird will fly through this arc, be struck by a blade, and be killed (Hodos et al. 2001).
Howell and Noone (1992) estimated U.S. avian mortality at 0.0 to 0.117 birds/turbine/yr., while in Europe, Winkelman (1992) estimated mortality at 0.1 to 37 birds/turbine/yr. Erickson et al. (2001) reassessed U.S. turbine impact, based on more than 15,000 turbines (some 11,500 n California), and estimated mortality in the range of 10,000 to 40,000 (mean = 33,000), with an average of 2.19 avian fatalities/turbine/yr. And 0.033 raptor fatalities/turbine/yr. This may be a considerable underestimate.
In addition to protections under the Migratory Bird Treaty Act, Bald and Golden Eagles, are afforded protection under the Endangered Species Act for the former and the Bald and Golden Eagle Protection Act for both raptors. Wind farms can affect local populations of Golden Eagles and other raptors whose breeding and recruitment rates are naturally slow and whose populations tend to have smaller numbers of breeding adults (Davis 1995). Raptors also have a lower tolerance for additive mortality (Anderson et al. 1997).
Literature Cited
Adams, R.A. 2003. Bats of the Rocky Mountain West. Natural History, Ecology and Conservation. University Press of Colorado, Boulder. 289 pp.
Anderson, R.L., H. Davis, W. Kendall, L.S. Mayer, M.L. Morrison, K. Sinclair, D. Strickland, and S. Ugoretz. 1997. Standard metrics and methods for conducting avian/wind energy interaction studies. Pp. 265-272 in G. Miller (editor). Windpower "97 Proceedings, June 15-18, 1997, Austin, TX, American Wind Energy Association.
Avian Powerline Interaction Committee. 1994. Mitigating bird collisions with powerlines: the state of the art in 1994. Edison Electric Institute. Washington, D.C. 78 pp.
Avian Powerline Interaction Committee. 1996 (reprinted 2000). Suggested practices for raptor protection on powerlines: the state of the art in 1996. Edison Electric Institute/Raptor Research Foundation, Washington D.C. 125 pp.
Berg, P. 1996. The effects of avian impacts on the wind energy industry. Undergraduate Engineering Review, Department of Mechanical Engineering, University of Texas, Austin. 9 pp.
Davis, H. (editor). 1995. A pilot Golden Eagle population study in the Altamont Pass Wind Resource Area, California. National Renewable Energy Laboratory, Golden, CO., Contract No. DE-AC36-83CH10093.
Erickson, W.P., G.D. Johnson, M.D. Strickland, K.J. Sernka, and R.E. Good. 2001. Avian collisions with wind turbines: a summary of existing studies and comparisons to other sources of avian collision mortality in the United States. Western Ecosystems Technology, Inc., Cheyenne, WY. National Wind Coordinating Committee Resource Document, August : 62 pp.
Federal Aviation Administration. 2000. Obstruction marking and lighting. Advisory Cicular AC 70/7460-1K, Air Traffic Airspace Management, March 2000. 31 pp.
Hodos, W., A. Potocki, T. Storm, and M. Gaffney. 2001. Reduction of motion smear to reduce avian collisions with wind turbines. Proceedings of the National Avian-Wind Power Planning Meeting IV:88-105.
Howell, J.D., and J. Noone. 1992. Examination of avian use and mortality at a U.S. windpower, wind energy development site, Montezuma Hills, Solano County, CA.
Orloff, S., and A. Flannery. 1992. Wind turbine effects on avian activity, habitat use and mortality in Altamont Pass and Solano County Wind Resource Areas. Report to the Planning Departments of Alameda, Contra Costa and Solano Counties and the California Energy Commission, Grant No. 990-89-003 to BioSystems Analysis, Inc., Tiburton, CA.
Winkelman, J.E. 1992. The impact f the SEP wind park near Oosterbierum (Fr.), the Netherlands, on birds, 2: nocturnal collision risks (Dutch, English summary). RIN report 92/3, DLO-Institute for Forestry and Nature Research, Arnhem. |
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