Wind Turbines

Bats and Turbines
 
As we strive to find alternative energy resources that are clean and renewable we must also make sure that the methods are safe for wildlife and their habitats.  As a conservation organization, we believe that using clean and renewable energy is a necessary goal that we must obtain.  However in reaching this goal we also must make sure that our plans and efforts keep negative impacts to wildlife at a minimum.  With wind energy at the forefront of alternative energy sources, wind turbine sites are growing and with this growth we also find an increase of bat and bird mortalities.  This is a worldwide issue and in North America alone, it is estimated that thousands of bats are dying due to wind turbines each year.  Bat mortality is found at nearly every wind facility site.  With the cooperation of wind energy organizations, scientists are working to reduce these fatalities, and understand why they are happening in the first place.  There are many questions that need to be answered when trying to understand this dire situation.  Unfortunately, not all of the 
questions have yet been answered, but researchers are performing many studies in an attempt to answer these questions.  We don't fully understand why bats are dying at wind energy sites.  Nor do we fully understand why they are attracted to tall turbines, but not other human-made structures of similar height. 
 
Although we can't answer these questions in full detail, scientists are gathering some clues that will eventually lead us to a better understanding of this fatal attraction.  So lets take a look at what we do know.
 
The bats impacted the most at wind energy sites are a group of species known as migratory tree bats.  As the name suggests, these bats migrate in the spring and fall and they roost in trees.  North American bats that fall into this category are hoary bats (Lasiurus cinereus),  silver-haired bats (Lasionycteris noctivagans), and red bats (Lasiurus borealis and L. blossevillii).  All of these bats play key roles in the ecosystem. They help to balance insect populations with their insectivorous diets, which is also crucial to the farmers of North America and those that rely on their resources. In addition to these bats being the most commonly found deceased at the wind energy sites, a seasonal pattern also exists.  In the late summer and early fall, bat mortalities are at the highest.  This timing coincides with the migratory and breeding patterns of these species.
 
Many hypotheses are being tested to better understand these patterns and to also test for significant results gathered from the data collected.  Migration patterns of the bats are studied to identify their routes.  Using stable isotopes from the hair of deceased animals has allowed scientists to determine the originating location of the bats.  Many of them grew their fur away from the sites in which they were found, indicating that they were killed during migration.  Other theories are also being researched looking at tall objects possibly being used for mating areas of the tree bats.  Trial experiments are also underway to deter bats from the wind turbines using electromagnetic radiation.  Sampling with various acoustic surveying tools to obtain the best results for collecting data at these sites are also in progress.  Scientists are analyzing the curtailment of turbine cut-in speeds (the minimum wind speed level in which to turn on turbines) to both reduce bat morality and prevent economic loss. 
 
Collaborative planning between wind facilities and scientists for both future and current wind energy sites is crucial to the protection of wildlife and their habitats.  Many wind energy sites have allowed researchers access to their fields and have also been open to suggestions to reduce the detrimental impacts to wildlife.  Working together, we can obtain results that benefit wind energy advances without devastating wildlife. 
 
Resources and for more information:
© 2012 Organization for Bat Conservation
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