02

What Do We Know about Impacts & Risk Factors to Wildlife and Habitat?

To maximize wind energy’s benefits while addressing the risk to wildlife, a first step is to better understand the extent and nature of the risk. Risk is defined as the likelihood that adverse impacts will occur to individuals or populations of wildlife as a result of wind energy development and operation. The potential impacts of wind energy to wildlife can be grouped in two categories: collision impacts, which refer to fatalities resulting from collision of wildlife with turbines, and habitat-based impacts, which refer to habitat changes that affect the success of local or regional wildlife populations. Impacts are studied at individual projects, but by analyzing the results of many studies we can gain insights about risk factors and potential solutions, as well as potential cumulative and population-level impacts.
Types of Impacts & Risk Factors - Infographic by AWWI

Assessing Risk

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What is the likelihood that adverse impacts will occur to wildlife as a result of wind energy development and operation, and what are the ecological consequences of those impacts? Risk can be defined as a function of hazard, vulnerability, and exposure, either to individual animals or to a population. Analyzing fatality data collected over many years and at multiple projects can help us understand which species are most at risk of collision or losing habitat, and where and under what conditions. Risk models can help us predict the wildlife impacts that might result from a particular wind energy project and can also help us estimate cumulative impacts of wind energy development on a larger scale.

Collision Risk and Risk Factors

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Some birds and bats collide with wind turbines. By collecting data and asking research questions, we are improving understanding of what species are at risk, and where and why they are at risk, so that mitigation can be targeted where it is needed. At many wind energy facilities, regular searches are conducted for birds and bats that collided with turbines. Analyzing results from fatality studies from many facilities can give us insight into patterns of collision risk and risk factors, including how risk varies across time and space, and how specific variables, such as landscape features and weather patterns, may influence risk.

Habitat-Based Impacts

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Though wind facilities can extend over thousands of acres, a small fraction is occupied by turbine pads and access roads. For species that are more sensitive to changes in habitat, wind energy development and operation may result in displacement or changes in habitat use, and potentially in decreased survival, reproduction, and distribution. Prairie grouse, grassland songbirds, ducks, shorebirds, mule deer, and pronghorn are among the species studied with respect to habitat-based impacts of wind energy. Both impacts and habituation to changes in habitat may take several years to manifest, requiring multi-year studies examining various stages of species’ life cycles and comparison of impact and control sites to account for other factors affecting their populations.

Population Impacts

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For many species, wind energy’s adverse impacts do not have population-level effects. Current estimates suggest most bird species, especially songbirds, are at low risk of population-level impacts from wind energy, while raptors may be more vulnerable to such effects. Population-level impacts on migratory tree bats are a concern, and better information on population sizes is needed to evaluate potential impact to these species. Although recorded fatalities of cave-dwelling bat species are typically low at most wind energy facilities, additional mortality from collisions is a concern given major declines in these species due to white-nose syndrome. Greater access to data from all regions and better population estimates for some species are needed to better assess the effects of wind energy impacts.

CHAPTER 03

Landscape Assessment and Siting Practices to Address Risk to Wildlife and Habitat