With the price of crude oil approaching $100 per barrel, the continued volatility of foreign energy markets and increasing acceptance of the link between fossil fuels and climate change, the hunt for "clean, green" energy has spurred an alternative energy boom in the United States. One of the significant energy source investments is wind power development. Wind power production increased by 27 percent in 2006 and, so far in 2007, 2,300 megawatts (MW) have been installed. The wind industry estimates that a record-breaking 4,000 MW (enough electricity to power 1 million homes) of new wind power is likely by the end of the year, reports the Wildlife Management Institute.

Although wind power promises to reduce carbon emissions, wildlife managers are calling for improved planning for wind power siting to avoid or minimize negative impacts on wildlife and wildlife habitats. Tackling the issue head-on will be a new federal advisory committee, announced in late October by the U.S. Department of the Interior.

"By some estimates, wind power could provide clean and renewable electricity to meet up to 20 percent of the nation's energy needs," said Interior Secretary Dirk Kempthorne. "This committee will help examine issues, such as site selection and turbine design, so we can develop wind resources while protecting wildlife."

Information contained within two new reports likely will be considered during the committee's efforts. In September, The Wildlife Society (TWS) released a technical review of wind power development impacts on wildlife. The report discusses the effects of wind power on wildlife and makes recommendations about addressing these effects to protect native wildlife and their habitats. In addition, the Association of Fish and Wildlife Agencies (AFWA) reviewed the current siting requirements and wildlife guidelines in place in every state.

Wildlife impacts

"While wind power offers an array of benefits to developed and developing countries, wind energy is not environmentally neutral," commented Dr. Ed Arnett, Conservation Scientist with Bat Conservation International and chair of TWS's Technical Review Committee. "There are both direct and indirect consequences of wind energy facilities, including the often-overlooked impacts resulting from loss of habitat for wildlife due to construction, the footprint of the facility and increased human access."

Some of the earliest documentation of direct mortality of wildlife comes from the Altamont Pass Wind Resource Area in California, one of the oldest and largest wind farms in the country, where concerns for avian mortality were first raised in the late 1980s. The area, in the foothills of Alameda and Contra Costa counties, east of San Francisco, currently has approximately 5,400 turbines. Because the wind facility is located within the Pacific Flyway and is a migratory pathway for raptors, there have been particularly high rates of bird strikes by rotors since construction. Avian mortality estimates suggest that 880 to 1,300 birds are killed every year, including as many as 116 golden eagles, 300 red-tailed hawks, 333 American kestrels and 380 burrowing owls.

National averages for avian mortality range from 2.3 to 3.5 birds per MW. Of particular concern is that 78 percent of birds killed at facilities outside of California were species protected under the Migratory Bird Treaty Act.

The impact of wind power development on bats is less understood, but recent surveys have indicated potentially high mortality rates. Estimates of bat fatality from 21 studies located at 19 different facilities from 5 different regions in the United States and a Canadian province ranged from 0.9 to 53.3 bats per MW. Fatalities in the eastern part of the United States are heavily skewed to migratory, foliage-roosting species, which include the hoary bat, eastern red bat and tree-roosting silver-haired bat.

Wind power facilities also impact wildlife habitat. Habitat loss or fragmentation occurs as a result of site development, service roadways and turbine operation. The direct losses generally are small, with a rough average of 1.2 hectares per turbine during construction, and they typically are short term. Fragmentation of habitat, on the other hand, can lead to avoidance by animals that traditionally used it. Studies have shown that habitat within 110 meters of turbines had markedly decreased use by birds, and there is likelihood that such displacement may be long-term.

Avoidance of impacts

Reduction of negative habitat impacts can be achieved by proper assessment of potential wind power sites prior to development and by specific design and construction standards. Research and monitoring at wind sites are showing significant improvements when specific measures are taken earlier in the planning process to reduce potential impacts to wildlife and habitats.

Poorly sited facilities consistently show considerable impacts on wildlife, particularly in areas where birds and bats concentrate during migration and where there are rare species. Site location also is correlated strongly with the mortality of bats; wind power sites along forested ridgelines in the eastern United States have the highest documented fatalities of bats. Conducting detailed preconstruction studies at a proposed location and working with area wildlife managers to document wildlife use of the area, particularly by migratory birds and bats, can help to determine whether the location is appropriate for wind power development. It also can guide siting decisions.

Changes to turbine design and site construction can help reduce the impacts to wildlife and habitat. The "older generation" turbines were mounted on lattice towers 60 to 80 feet in height, with rotors 50 to 60 feet in diameter. They turned at rates of 60 to 80 revolutions per minute (rpm). The height of the towers placed the fast-revolving blades directly in the path of many migrating birds, and the use of lattice towers and above-ground wires provided perching areas attractive to raptors. Today's wind machines are mounted on towers 200 to 260 feet in height. Their rotors range from 150 to 260 feet in diameter and turn at rates of 11 to 28 rpm. Advanced technologies in turbine design and reducing habitat disturbance during construction can significantly reduce avian mortality or site avoidance.

Necessary guidelines

Conservation organizations and wildlife managers are becoming increasingly proactive in encouraging the inclusion of wildlife protection measures as part of wind power development. TWS's review concludes that, "given the projected development of wind energy, biologically significant cumulative impacts are possible for some species and may become more pronounced over time, unless solutions are found. Avoiding, minimizing, and mitigating harmful impacts to wildlife is [sic] an important element of 'green energy' and developers of wind energy sources should cooperate with scientists and natural resource agency specialists in developing and testing methods to minimize harm to wildlife."

However, ensuring that adequate wildlife protection guidelines are in place and implemented throughout the wind siting and development process is a challenge being faced by wildlife managers across the country. According to the AFWA report, 20 states have some form of guidelines for wind power siting and wildlife. However, only three of those have mandatory requirements, and there is great variability among the states on what the guidelines recommended. In addition, the actual permitting process for siting of wind power facilities is inconsistent, with only six states having wind-specific siting authority.

The Department of the Interior advisory committee-comprised of representatives from state and federal agencies, the wind industry, and conservation organizations-is expected to address some of the disparity in wind power siting requirements. Tasked with advising the U.S. Fish and Wildlife Service (Service) on measures to avoid or minimize impacts to wildlife and their habitats from land-based wind energy facilities, the committee will update the Service's guidelines and will provide a framework that wildlife managers will find applicable in all states. (jas)