A summary of bird mortality at photovoltaic utility scale solar facilities in the Southwestern U.S.

Karl Kosciuch,Michael Gerringer,Wallace Erickson,Daniel Riser-Espinoza

doi:10.1371/journal.pone.0232034

Abstract

Recent trends in renewable energy development in the United States (U.S.) show that new installed capacity of utility-scale solar energy has exceeded 30% of total installed capacity of all sources per year since 2013. Photovoltaic solar energy provides benefits in that no emissions are produced; however, there are potential impacts from photovoltaic solar development on birds that include habitat loss and potential for collision mortality. Only 2 papers in the peer-reviewed literature present fatality information from fatality monitoring studies at a photovoltaic utility-scale solar energy facility; however, more data exists in unpublished reports. To provide a more comprehensive overview of bird mortality patterns, we synthesized results from fatality monitoring studies at 10 photovoltaic solar facilities across 13 site-years in California and Nevada. We found variability in the distribution of avian orders and species among and within Bird Conservation Regions, and found that water-obligate birds, which rely on water for take-off and landing, occurred at 90% (9/10) of site-years in the Sonoran and Mojave Deserts Bird Conservation Region. We found that a cause of mortality could not be determined for approximately 61% of intact carcasses, and that approximately 54% of all carcasses were feather spots, introducing uncertainty into the interpretation of the fatality estimates. The average annual fatality estimate we calculated for photovoltaic solar (high-end estimate of 2.49 birds per megawatt per year) is lower than that reported by another study (9.9 birds per megawatt per year) that included one photovoltaic facility. Our results provide a summary of fatalities in bird conservation regions where the facilities are located, but expanding our conclusions to new regions is limited by the location of facilities with fatality monitoring data.

Highlights

Recent trends in renewable energy development in the United States (U.S.) show that new installed capacity of utility-scale solar energy (USSE) has exceeded 30% of total installed capacity of all energy sources per year since 2013 [1]
We identified useable data that met our inclusion criteria from 13 site-years occurring between November 2013 and September 2018 at 10 PV USSE facilities located in southern California in Imperial, Riverside, San Bernardino, and San Luis Obispo counties, and Nevada in Clark and Mineral counties (Fig 2; S2 Appendix)
A phenology pattern emerged where most detections occurred in fall in the Sonoran and Mojave Deserts (SMD) Bird Conservation Region (BCR), with a pattern of higher detections occurring through winter in the Coastal California (CC) BCR

Summary

Methods

We used several sources of information to obtain studies on bird fatality rates at PV USSE. We conducted an internet-based search for studies on avian mortality at solar facilities in a manner similar to that of Walston et al [6]. We used Google [13] and Web of Science [14] to search the term “solar energy” in various combinations with bird, avian, death, fatality, monitoring, mortality, and report. As fatality monitoring reports at PV USSE could be available outside of the peer-reviewed literature, we obtained studies on standardized surveys for avian mortality at PV USSE from state and federal agencies, and from solar energy developers and operators. We excluded any studies of residential PV or studies of concentrated solar power or solar trough technologies.

Results

Discussion

Conclusion