The growth of alternative energy development in desert ecosystems has the potential to impact the acoustic ecology of aerial and terrestrial species. Wind energy facilities produce high levels of broadband noise during construction, operation, and decommission. Noise impacts have been well documented for many animals. Impacts include: change in habitat use, behavioral shifts, increased stress levels, higher predation risk, and degradation in communication. We used calibrated acoustic recording units at the Mesa Wind Energy Facility in the San Bernardino Mountains in Southern California to determine the ambient sound levels and bioacoustic activity while turbines were operating and following a facility shutdown. Acoustic recordings were collected adjacent to the wind energy facility as well as 1.5km away from the facility. A subset of acoustic data was analyzed for the presence of biological activity. Analysis involved listening to ten second clips, sampled every two minutes for the presence of biological sounds (e.g. birds, bats, rodents, insects) and anthropogenic sources (e.g. wind turbines, aircraft). Percent of samples with each acoustic source was compared at the near site before and after the wind energy facility was shutdown. When the turbines were on, bioacoustical activity was compared at the near and far site.
Ambient sound levels (L50) at the near site during wind turbine operation ranged between 53-56.1 SPL dBA. After shutdown sound levels decreased to a range of 34.7-37.6 SPL dBA. This difference in sound level, represents a theoretical decrease in listening area of 98%. A variety of biological sounds were detected only after the facility shutdown. When the facility shutdown, bioacoustic activity increased by 14%. Most of the increased activity was from insects and birds.
When wind turbines were operational ambient sound levels at the near site were16.1dB higher than the far site. Bioacoustic activity at the near site was present in 0% of samples whereas the far site had bioacoustic detections in 41.25% of samples. Most of the detected bioacoustic activity was from insects and birds. Future analysis will include a characterization of wind energy facility noise to determine the potential masking effects on biological signals. These results provide important insights into the potential impacts of alternative energy development on the acoustic ecology of desert organisms.
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