The construction and operation of a wind farm will have some local impact to the natural environment, but the specific impacts are site specific. Effects can include avian (bird), bat, and other wildlife activity. Some of the following documents are available as Adobe Acrobat PDFs. Download Adobe Reader.
Largely because of the unique circumstances and experiences surrounding one region in Northern California with significant wind energy development in the 1980s, wind power proponents now conduct wildlife (and particularly avian) studies as a regular part of screening sites for development. Earlier generations of wind turbines were smaller and located close together. They were mounted on lattice towers and had rapidly spinning blades. These wind turbines were located in great numbers in the Altamont Pass, an area of rolling grassland home to a substantial population of raptors. A high number of bird kills resulted. Wind technology has advanced substantially since the 1980s. Today's larger turbines have wider spacing, more slowly spinning blades, and are mounted on tubular towers. Nonetheless, wind turbines, like all manmade structures, do have the potential to impact birds and/or bats. Careful selection of development sites avoids placement in particularly sensitive locations, and for well-sited wind projects, avian impacts can be minimal including relative to other sources of avian collision. The National Wind Coordinating Collaborative published a report discussing bird interaction with wind turbines in the Spring of 2010, "Wind Turbine Interactions with Birds, Bats, and their Habitats: A Summary of Research Results and Priority Questions (PDF 2.0 MB)."
Still, in the forefront of discussions around the environmental impacts of wind energy projects is the interaction of wind farms with birds of particular concern to wildlife agencies: migrating and endangered species. As a result of this concern and their role in protecting this wildlife, the U.S. Fish and Wildlife Service (USFWS) issued interim guidelines on May 13, 2003 regarding the development of wind energy projects and compliance with the Endangered Species Act (ESA) and the Migratory Bird Treaty Act (MBTA).
On April 13. 2010, the Wind Turbine Guidelines Advisory Committee transmitted its final recommendations (PDF 2.3 MB) to the Secretary of the Interior through the U.S. Fish and Wildlife Service. The committee was formed in 2007 under the Federal Advisory Committee Act, to provide advice and recommendations on how to avoid and minimize the impacts of land-based wind farms on wildlife and its habitats.
As summarized in the report, the Committee's Guidelines are founded upon a "tiered approach" for assessing potential impacts to wildlife and their habitats. The tiered approach is an iterative decision-making process for collecting information in increasing detail, quantifying the possible risks of proposed wind energy projects to wildlife and habitats, and evaluating those risks to make siting, construction, and operation decisions. The tiers include:
- Tier 1 — Preliminary evaluation or screening of sites (landscape-level screening of possible project sites)
- Tier 2 — Site characterization (broad characterization of one or more potential project sites)
- Tier 3 — Field studies to document site wildlife conditions and predict project impacts (site-specific assessments at the proposed project site)
- Tier 4 — Post-construction fatality studies (to evaluate direct fatality impacts)
- Tier 5 — Other post-construction studies (to evaluate direct and indirect effects of adverse habitat impacts, and assess how they may be addressed).
This framework allows the developer to determine whether he or she has sufficient information, whether and/or how to proceed with development of a project, or whether additional information gathered at a subsequent tier is necessary to make those decisions.
The Committee agrees that incentives should be available to those developers who demonstrate due care by voluntarily implementing the tiered approach and through coordination with the U.S. Fish and Wildlife Service early and throughout the tiered process. The Committee recognizes substantial variability among project sites and recommended methods and metrics that should be applied flexibly on a site-by-site basis, while maintaining consistency in the overall tiered process. Other elements in the Guidelines include a full discussion of mitigation policies and principles; the applicability of adaptive management, including the potential use of operational modifications; and considerations related to cumulative impacts, habitat fragmentation, and landscape-level analysis. Finally, the Guidelines discuss the need for additional research and collaboration related to potential wind energy-wildlife impacts, and offer some alternatives for accomplishing the needed research.
Similar attention is now being given to the impact of wind farms on bats. Until recently, no material impacts on bat communities from wind power installations had been observed. However, an incident in which a fairly substantial number of bat fatalities occurred at the site of a West Virginia wind farm has stimulated substantial attention to understanding and mitigating potential impacts to bats. Little is currently known about bat interaction with wind turbines, and both industry and wildlife organizations have been collaborating on studying and understanding how bats interact with wind turbines. The issue is continuing to become a focus in the permitting process of wind farms in areas where bats are known to exist. A 2005 study by the Government Accountability Office entitled "Wind Power Impacts on Wildlife and Government Responsibilities for Regulating Development and Protecting Wildlife" (PDF 1.7 MB) is available. General information specifically on bats and wind turbines can be found at the Bat Conservation International, Inc. Web site.