Expert Report


There has been rapid growth in the construction of wind-powered electricity generating facilities over the past 25 years in the United States. Wind-energy facilities emit no atmospheric pollutants and are driven by a renewable source, addressing multiple environmental concerns such as air quality and climate change. But the expansion of such facilities can carry adverse environmental impacts. As wind energy development continues to expand, federal, state and local agencies should adopt a coordinated approach to evaluating the planning, regulation, and location of wind-energy projects. This National Research Council report provides a framework that can help in evaluating tradeoffs between the benefits of new wind-energy projects and risks of adverse environmental impacts before projects begin.

Key Messages

  • A better analysis of the cumulative effects of various anthropogenic energy sources, including wind turbines, on bird and bat fatalities is needed, especially given projections of substantial increases in the numbers of wind turbines in coming decades.
  • Although methods for assessing aesthetic impacts need to be adapted to the particular characteristics of wind-energy projects, such as their visibility, the basic principles of systematically understanding the relationship of a project to surrounding scenic resources apply and can be used to inform siting and regulatory decisions.
  • At the current level of wind-energy development the committee sees no evidence that fatalities caused by wind turbines result in measurable demographic changes to bird populations in the United States, with the possible exception of raptor fatalities in the Altamont Pass area, although data are lacking for a substantial portion of the operating facilities.
  • Because wind energy is new to many state and local governments, the quality of processes for permitting wind-energy developments is uneven in many respects.
  • Choosing the level of regulatory authority for reviewing wind-energy proposals carries corresponding implications for how the following issues are addressed: (1) cumulative effects of wind-energy development;(2) balancing negative and positive environmental and socioeconomic impacts of wind energy; and (3) incorporating public opinions into the review process.
  • Electricity generated from different sources is largely fungible. Depending on factors such as price, availability, predictability, regulatory and incentive regimes, and local considerations, one source might be preferentially used over others.
  • Electricity generated in the MAH including wind energy is used in a regional grid in the larger mid-Atlantic region. Electricity generated from wind energy in the MAH has the potential to displace pollutant emissions, discharges, wastes, and other adverse environmental effects of other sources of electricity generation in the grid. That potential is estimated to be less than 4.5%, and the degree to which its beneficial effects would be realized in the MAH is uncertain.
  • If the future were to bring more aggressive renewable-energy-development policies, potential increased energy conservation, and improved technology of wind-energy generation and transmission of electricity, the contribution of wind energy to total electricity production would be greater.
  • Not enough information is available to form a reliable judgment on whether the number of bats being killed will have overall effects on populations, but given a general region-wide decline in the populations of several species of bats in the eastern United States, the possibility of population effects, especially with increased numbers of turbines, is significant.
  • There are systematic and well-established methods for assessing and evaluating human impacts; they allow better informed and more-enlightened decision making.
  • There is insufficient information available at present to form a reliable judgment on the likely effect of all the proposed or planned wind energy installations in the mid-Atlantic region on bird and bat populations.
  • There is little anticipatory planning for wind-energy projects, and even if it occurred, it is not clear whether mechanisms exist that could incorporate such planning in regulatory decisions.
  • Using an evaluation guide to organize regulatory review processes can help to achieve comprehensive and consistent regulation coordinated across jurisdictional levels and across types of effects.
  • Using the future projections of installed U.S. energy capacity by the DOE, the committee estimates that wind-energy development probably will contribute to offsets of approximately 4.5% in U.S. emissions of CO2 from electricity generation by other electricity-generation sources by the year 2020. In 2005, electricity generation produced 39% of all CO2 emissions in the United States.
  • Well-specified, formal procedures for regulatory review enhance predictability, consistency, and accountability for all parties to wind-energy development.
  • Wind energy will contribute proportionately less to electricity generation in the mid-Atlantic region than in the United States as a whole, because a smaller portion of the region has high-quality wind resources than the portion of high-quality wind resources in the United States as a whole.
  • The environmental benefits of wind-energy development, mainly reductions in atmospheric pollutants, are enjoyed at wide spatial scales, while the environmental costs, mainly aesthetic impacts and ecological impacts, such as increased mortality of birds and bats, occur at much smaller spatial scales. There are similar, if less dramatic, disparities in the scales of realized economic and other societal benefits and costs. The disparities in scale, although not unique to wind-energy development, complicate the evaluation of tradeoffs.